The On-Board Diagnostic (OBD) system is a crucial component of modern vehicles, acting as the car’s internal health monitor. Since the introduction of OBDII in the mid-1990s, this standardized system has revolutionized how we diagnose and maintain our cars. Whether you’re a seasoned mechanic or a car owner keen on understanding your vehicle better, grasping the basics of OBD2 tests is essential. While some might mistakenly believe tools like a Cen-Tech OBD2 scanner adds miles to odometer, the reality is far more about diagnostics and ensuring your vehicle runs efficiently and cleanly.
This comprehensive guide delves into the world of OBD2 testing, drawing from established standards and addressing common issues encountered during vehicle inspections. We’ll explore the pass/fail criteria for OBD tests, delve into readiness monitors, malfunction indicator lamps (MILs), communication protocols, and even permanent diagnostic trouble codes (PDTCs). Understanding these aspects is key to navigating smog checks and ensuring your vehicle meets emission standards. Furthermore, we will shed light on specific vehicle models known to have OBD system quirks, providing insights for both vehicle owners and technicians.
Understanding OBD2 Smog Check Inspection Standards
Smog checks, or emission tests, are mandatory in many regions to ensure vehicles meet environmental regulations. A significant part of these inspections involves the OBD2 system. The OBD test evaluates various emission control systems and reports any malfunctions. Here’s a breakdown of the key pass/fail standards:
Readiness Monitors: Ensuring System Self-Checks
Readiness monitors are self-diagnostic tests run by your car’s computer to verify that emission control systems are functioning correctly. These monitors cover components like the oxygen sensors, catalytic converter, evaporative system, and more. For a vehicle to pass an OBD smog check, most of these monitors need to be in a “ready” state, indicating they’ve completed their self-tests and found no issues.
However, not all monitors need to be complete. The allowable number of incomplete monitors depends on the vehicle’s model year and fuel type:
| Model Year | Fuel Type | Incomplete Monitors Allowed |
|---|---|---|
| 1996-1999 | Gasoline | Any one |
| 2000 and newer | Gasoline | Evaporative system only |
| 1998-2006 | Diesel | Zero |
| 2007 and newer | Diesel | Particulate Filter and NMHC |
It’s important to note that continuous monitors like misfire, fuel system, and comprehensive components are typically ignored during OBD tests on gasoline vehicles. If your vehicle fails a smog check due to incomplete monitors, it doesn’t necessarily mean there’s a malfunction. It might simply require a specific drive cycle to allow the monitors to run and complete. Vehicle owner’s manuals or repair service literature sometimes provide these drive cycle procedures.
Malfunction Indicator Lamp (MIL): The “Check Engine Light”
The Malfunction Indicator Lamp, commonly known as the “Check Engine Light,” is a crucial indicator of potential issues within your vehicle’s emission control systems. The MIL’s behavior during an OBD test is a straightforward pass/fail criterion:
| Condition | Result | Standard |
|---|---|---|
| MIL illuminates when key is turned to “ON” (engine off) | Pass | System check – bulb is working |
| MIL turns off when engine is running | Pass | No active emissions-related faults detected |
| MIL does not illuminate when key is turned to “ON” (engine off) | Fail | Bulb malfunction or system fault |
| MIL remains illuminated when engine is running | Fail | Active emissions-related fault detected |
A failing MIL status is a clear indication of a problem that needs attention. It’s essential to address the underlying issue causing the MIL to illuminate to ensure your vehicle runs efficiently and passes emission tests.
Communication Standards: Establishing a Connection
For an OBD test to proceed, the diagnostic tool must successfully communicate with the vehicle’s computer. Communication failures can stem from various sources, including:
- Damaged OBD connector or wiring
- Aftermarket stereo installations interfering with the system
- Incorrect computer response (e.g., transmission computer instead of engine computer)
- Invalid data from the vehicle
The communication standards are simple:
| Test Type | Standard |
|---|---|
| BAR-97 | Vehicle communicates with BAR-97 analyzer |
| OIS | Vehicle communicates with OIS and transmits required data |
Required data typically includes information from OBD addresses Mode $01 PID $00 and Mode $01 PID $01, which provide details about supported data parameters, MIL status, diagnostic trouble codes (DTCs), and monitor status. If communication fails, troubleshooting the connection and vehicle’s OBD system is necessary.
Permanent Diagnostic Trouble Codes (PDTCs): Persistent Fault Indicators
Permanent Diagnostic Trouble Codes (PDTCs) were introduced to address the issue of clearing DTCs just before a smog check to temporarily hide problems. PDTCs are similar to regular DTCs but cannot be erased by simply using a scan tool or disconnecting the battery. They can only be cleared by the OBD II system itself after verifying that the fault condition is no longer present, usually after the vehicle has been driven through several drive cycles without the issue reoccurring.
Since July 1, 2019, PDTC checks have become part of BAR-OIS Smog Check inspections. The standards are as follows:
| Model Year | Standard |
|---|---|
| 1996-2009 | Not applicable |
| 2010 and newer | Vehicles fail if a PDTC is present |
A vehicle will fail the PDTC check even if the MIL is off. However, PDTC presence is ignored if the vehicle has completed at least 15 warm-up cycles and been driven 200 miles since the OBD information was last cleared. It’s also worth noting that some vehicles have known issues with clearing certain PDTCs, and these are often addressed by vehicle manufacturers through recalls or extended warranties.
Modified Software Standards: Upholding Emission Integrity
To prevent tampering with vehicle emission controls, modified software checks were added to BAR-OIS Smog Check inspections on July 19, 2021. Software that has been approved by the California Air Resources Board (CARB) through an Executive Order is permissible. However, any illegally modified software that alters emission controls will result in a Smog Check failure.
Vehicles with modified software will fail the inspection, and the report will indicate “Modified Software.” To pass, the vehicle must be restored to an OEM-approved or CARB-approved software configuration. Consumers who wish to dispute inspection results can contact the Smog Check Referee.
Vehicles of Interest: Navigating Known OBD Test Issues
Certain vehicle models are known to exhibit specific issues during OBD tests. These issues can range from communication problems and incomplete readiness monitors to false MIL illumination. In many cases, the inspection systems are programmed to accommodate these known anomalies. However, in some situations, vehicle repair may be necessary.
Here are some vehicles of interest, categorized by the type of OBD test issue:
OIS Vehicles of Interest: Common OBD Inspection Quirks
This section highlights gasoline, flex-fuel (model-year 2000 and newer), and diesel (model-year 1998 and newer) vehicles with known OBD test issues during an OIS (OBD Inspection System) inspection.
| Make | Year | Model & Engine | Issue | Cause & Remedy | Inspector Instruction |
|---|---|---|---|---|---|
| Audi | 2000-2004 | A4 & A6 | No OBD communication | Broken ground wire in ABS module | Repair per Audi TSB #A45-15-10 |
| BMW | 6/1/99 – 7/31/00 | 323i Sedan | Oxygen sensor monitor not set | DME Software error | Check DME number in TSB #SI B12 16 16, reprogram DME |
| BMW | 9/3/99 – 7/31/00 | 323iT Touring | Oxygen sensor monitor not set | DME Software error | Check DME number in TSB #SI B12 16 16, reprogram DME |
| BMW | 6/1/99 – 7/29/00 | 323Ci Coupe | Oxygen sensor monitor not set | DME Software error | Check DME number in TSB #SI B12 16 16, reprogram DME |
| BMW | 6/23/99 – 7/29/00 | 323 Cic Convertible | Oxygen sensor monitor not set | DME Software error | Check DME number in TSB #SI B12 16 16, reprogram DME |
| BMW | 2000 | M52 (TU) engine | Oxygen sensor monitor not set | DME Software error | Check DME number in TSB #SI B12 16 16, reprogram DME |
| BMW | 2000 | Readiness failure, oxygen sensor monitor | Software error in ECM | Reflash ECM per Recall #00E-A01, BMW bulletin #SI B 12 15 99 | |
| BMW | built 3/98 – 7/99 | 323i, 323iA, 328i, 328iA | Readiness failure, oxygen sensor monitor | Software error in ECM | Reflash ECM per Recall #00E-A01, BMW bulletin #SI B 12 15 99 |
| BMW | built 2/99 – 7/99 | 328iC, 328iCA, 323iC, 323iCA, 528i, 528iA, 528iT, 528iAT | Readiness failure, oxygen sensor monitor | Software error in ECM | Reflash ECM per Recall #00E-A01, BMW bulletin #SI B 12 15 99 |
| BMW | built 9/98 – 7/99 | Z3 roadster 2.3 | Readiness failure, oxygen sensor monitor | Software error in ECM | Reflash ECM per Recall #00E-A01, BMW bulletin #SI B 12 15 99 |
| BMW | built 4/99 – 7/99 | Z3 roadster coupe/ roadster 2.8 | Readiness failure, oxygen sensor monitor | Software error in ECM | Reflash ECM per Recall #00E-A01, BMW bulletin #SI B 12 15 99 |
| BMW | 2001-2003 | Z3 M Roadster/coupe with S54 engine | No communication when ignition off/on | ECM software issue, Recall Campaign | Follow OIS prompts, connect/disconnect DAD when key off |
| BMW | 2000-2003 | Z8 & M5 with S62 engine | No communication when ignition off/on | ECM software issue, Recall Campaign | Follow OIS prompts, connect/disconnect DAD when key off |
| BMW | Up to 8/27/2004 | M3 with S54 engine | No communication when ignition off/on | ECM software issue, Recall Campaign | Follow OIS prompts, connect/disconnect DAD when key off |
| BMW | 2003 | M3 | EGR monitor failure | Thermostat issue | Repair and retest |
| BMW | 2007 | 328i | Engine dies during OBD test | Keyless ignition issue | Separate key, wait 20+ min, restart, test normally |
| Chevrolet | 1998-2005 | DIESEL C/K2500 & C/K3500, G30, G3500, P30 (Federal diesel >8500 GVWR) | Not OBD-II certified | Federal diesel vehicles over 8,500 GVWR not OBD-II compliant | Test normally, OIS ignores continuous monitors, bulb check if no communication |
| Chevrolet | 1999-2005 | 3500 W35042 (box truck) (diesel, Federal certified) | Not OBD II equipped | OBD not installed in federal vehicles in this GVWR range | OIS skips OBD functional test |
| Chevrolet | 2000-2002 | S-10 (2WD), 2.2L I-4 (E85) | Monitors don’t set on flex fuel models | System monitors disabled for >E15 blends | OIS ignores all 11 readiness monitors |
| Chevrolet | 2000-2005 | Suburban, Silverado, Express, Avalanche (gasoline, Federal certified) | “Unable to confirm OBD II requirements” message | Federally certified vehicle may not be OBD II certified | Check under-hood label, enter result, follow OIS prompts, BAR-97 test possible |
| Chevrolet | 2001 | Silverado / Tahoe C/K 1500 | Secondary air system monitor failure | Air injection problem | Diagnose, repair and retest |
| Chevrolet | 2002 | Silverado C/K 2500HD (diesel) | EGR monitor failure | Difficult drive cycle | OIS reprogrammed to allow incomplete monitor |
| Chevrolet | 2001-2002 | Cavalier CNG (Mexico built) | CAT monitor failure | Vehicle design anomaly | OIS allows one incomplete monitor |
| Chevrolet | 2019 | Express 2.8L (diesel, CA certified) | Exhaust Gas Sensor monitor incomplete | ECM diagnostic handling issue | ECM reflash per Recall N232408230, retest |
| Chrysler | 1999-2000 | Town & Country 3.0L (built after 12/1/98) | EGR Monitor incomplete at high altitude | Reflash available | Reflash PCM per TSB 18-03-00, retest |
| Chrysler | 2000 | Town and Country 3.3L V-6 (E-85) | Readiness monitors don’t set on flex fuel models | All monitors disabled for >E30 | OIS ignores all 11 readiness monitors |
| Chrysler | 2003 | PT Cruiser 2.4L turbo 5-spd manual | Catalyst monitor failure | PCM software error | PCM reflash per TSB #18-112-16, lifetime warranty |
| Chrysler | 2010 (built before 2/20/10) | 300, Charger, Challenger 3.5L (5-spd auto) | Readiness failure, MIL P0456, P0452, P1115 | Reflash available | Reflash per TSB #18-008-10, retest |
| Dodge | 1998-2002 | Ram Truck 5.9L (Cummins diesel, CA certified) | Continuous monitors incomplete | Vehicle design anomaly | Test normally, OIS allows one incomplete continuous monitor |
| Dodge | 1998-2006 | Ram 2500, Ram 3500 (diesel, Federal certified >8500 GVWR) | Not OBD-II certified | Federal diesel vehicles over 8,500 GVWR not OBD-II compliant | Test normally, OIS ignores continuous monitors, bulb check if no communication |
| Dodge | 1999-2000 | Caravan 3.0L (built after 12/1/98) | EGR Monitor incomplete at high altitude | Reflash available | Reflash PCM per TSB 18-03-00, retest |
| Dodge | 2003 | Dakota, Durango, Ram 4.7L (CA or 50-state certified) | Catalyst monitor “not supported” | Broken vehicle, repair needed | Test normally, OIS ignores unsupported monitors |
| Dodge | 2003 | Ram Truck 5.9L (Cummins diesel, CA certified) | MIL on, no DTCs stored | Vehicle design anomaly, Recall #K01 | Test normally, OIS ignores MIL command if no DTCs, advise of Recall #K01 |
| Dodge | 2003-2004 | 2500 4X2, Sprinter 3500 4X2 (diesel, 2003/2004 Federal certified >8500 GVWR) | Not OBD-II certified | Federal diesel vehicles over 8,500 GVWR not OBD-II compliant | Test normally, OIS ignores continuous monitors, bulb check if no communication |
| Dodge | 2004-2005 (built after 12/7/03) | Ram Truck 5.9L (Cummins diesel, CA certified) | Comprehensive component monitor incomplete | Vehicle design anomaly, TSB #18-030-10, lifetime warranty | Test normally, OIS allows one incomplete monitor, advise of fix with lifetime warranty TSB #18-003-11 |
| Dodge | 2004-2006 | 2500 3500 Sprinter (diesel) | EGR/VVT monitor incomplete | ECU software error | Test normally, OIS ignores EGR/VVT monitor |
| Dodge | 2005 | Ram Truck 5.9L (Cummins diesel, Federal certified) | Misfire, Comprehensive Component monitors incomplete | Vehicle design anomaly | Test normally, OIS ignores misfire and comprehensive component monitor readiness |
| Dodge | 2006-2007 | Ram Truck 5.9L, 6.7L (Cummins diesel, CA certified) | Fuel System, Comprehensive Component monitors incomplete | Recall #K01 | Test normally, OIS ignores fuel and comprehensive component monitor readiness, advise of Recall #K01 |
| Dodge | 2006-2007 | Ram Truck 5.9L (ETC/ETH after 1/1/06, Federal), Cab Chassis 6.7L (ETJ before 1/11/07, Federal) (Cummins diesel) | Fuel System, Comprehensive Component monitors incomplete | TSB #18-017-10 | Test normally, OIS ignores fuel and comprehensive component monitor readiness, advise of TSB #18-017-10 |
| Dodge | 2010 (built before 2/20/10) | 300, Charger, Challenger 3.5L (5-spd auto) | Evaporative monitor not set | Evaporative leak detection monitor issue | Test normally, inform consumer of TSB #18-008-10 Revision A |
| Dodge/Ram | 2010-2015 | 2500 & 3500 6.7L (diesel, CA certified) | NOx after-treatment monitor incomplete | Vehicle design anomaly | Test normally, OIS temporarily allows NOx after-treatment monitor incomplete |
| Dodge/Ram | 2014 | ProMaster 2500 & 3500 High 3.0L (diesel, CA certified) | Exhaust Gas Sensor monitor incomplete | Vehicle design anomaly, Recall V97, ZC0 | Reflash, perform recall, retest |
| Dodge/Ram | 2015 | ProMaster 1500, 2500, & 3500 High & Standard 3.0L (diesel, CA certified) | Exhaust Gas Sensor monitor incomplete | Vehicle design anomaly, Recall V97, ZC0 | Reflash, perform recall, retest |
| Dodge/Ram | 2016 | ProMaster 2500 & 3500 High 3.0L (diesel, CA certified) | Exhaust Gas Sensor monitor incomplete | Vehicle design anomaly, Recall V97 | Reflash, perform recall, retest |
| Ford | 1998-2003 | Truck 7.3L (diesel) | Engine shut off with Mode $09 data request | Vehicle design anomaly | Test normally, OIS skips Mode $09 data request |
| Ford | 1998-2004 | F250, F350, E350, E450, E Super Duty, Econo Commercial S- Duty, Econo RV S- Duty (diesel, Federal certified >8500 GVWR) | Not OBD-II certified | Federal diesel vehicles over 8,500 GVWR not OBD-II compliant | Test normally, OIS ignores continuous monitors, bulb check if no communication |
| Ford | 2000-2004 | F250, F350, E350, Excursion (gasoline, Federal certified) | “Unable to confirm OBD II requirements” message | Federally certified vehicle may not be OBD II certified | Check under-hood label, enter result, follow OIS prompts, BAR-97 test possible |
| Ford | 2003 | Focus | Readiness failure | Monitors difficult to complete | Reflash PCM per TSB #06-7-5, retest |
| Ford | 2004 | E350 Super duty 5.4 (gas) | CAT monitor failure | Vehicle design anomaly, Recall #15E06 | Reflash ECM, repair per recall, retest |
| Ford | 2011 | Edge, Explorer 3.5L & 3.7L | Readiness failure | OBD-II data clearing/VIN reporting issue | Consult Ford Emission Recall #13E04, ensure recall performed, complete drive cycles |
| Ford | 2013-2016 | F series, Super Duty 6.7L (diesel) | Exhaust Gas Sensor monitor incomplete | EGS monitor degreening strategy after DOC/DPF replacement (6000-10000 miles) | Test normally, OIS ignores EGS monitor on certain VINs until 10/8/2025 |
| Ford | 2015-2019 | Transit 3.2L (diesel) | Exhaust Gas Sensor monitor incomplete | EGS monitor degreening strategy after DOC/DPF replacement (6000-10000 miles) | Test normally, OIS ignores EGS monitor on certain VINs until 10/8/2025 |
| Ford | 2020-2022 | Escape (all engines, gasoline & hybrid) | No communication | Design issue, software update available | Direct to Ford dealer for software update, see SSM 50974 |
| Ford | 2021-2022 | Bronco Sport (all engines, gasoline not hybrid) | No communication | Design issue, software update available | Direct to Ford dealer for software update, see SSM 50974 |
| Ford | 2021-2023 | E350, E450 (all engines, gasoline not hybrid) | No communication | Design issue, software update available | Direct to Ford dealer for software update, see SSM 50974 |
| Ford | 2025 and newer | Explorer (2.3L) AWD, RWD (Test Group SFMXT02.34K2) | No OBD communication | OBDonUDS, DAD 1.0 incompatible | Cal-VIS skips OBD test until DAD 2.0 certified |
| Freightliner | 1998-2004 | M Line Walk In Van (diesel, Federal certified, GVWR 6,001-14,000) | Not OBD II equipped | OBD not required in federal vehicles in this GVWR range | OIS skips OBD functional test |
| Freightliner | 2004-2006 | Sprinter (diesel) | EGR/VVT monitor incomplete | ECU software error | Test normally, OIS ignores EGR/VVT monitor |
| GM | 2000 – 2008 | Various models, Silverado 1500 | No vehicle voltage prompt | No power on OBDII connector (DLC pin 16) | Use auxiliary DAD cables/power supply |
| GM | 2015-2017 | All gasoline powered | Readiness failure | Post catalyst oxygen sensor monitor break-in (1000 miles) | Inspect after 1000 miles or send to Referee |
| GMC | 1998-2005 | DIESEL C/K2500 & C/K 3500, Savana G3500, Workhorse P30 (Federal diesel >8500 GVWR) | Not OBD-II certified | Federal diesel vehicles over 8,500 GVWR not OBD-II compliant | Test normally, OIS ignores continuous monitors, bulb check if no communication |
| GMC | 1999-2005 | W3500 W35042 (box truck) (diesel, Federal certified, GVWR 10,001 – 14,000) | Not OBD II equipped | OBD not required in federal vehicles in this GVWR range | OIS skips OBD functional test |
| GMC | 2000-2002 | Sonoma (2WD), 2.2L I-4 (E85) | Monitors don’t set on flex fuel models | System monitors disabled for >E15 blends | OIS ignores all 11 readiness monitors |
| GMC | 2000-2005 | Sierra, Yukon, Savana (gasoline, Federal certified) | “Unable to confirm OBD II requirements” message | Federally certified vehicle may not be OBD II certified | Check under-hood label, enter result, follow OIS prompts, BAR-97 test possible |
| GMC | 2002 | Sierra C/K 2500HD (diesel) | EGR monitor failure | Difficult drive cycle | OIS reprogrammed to allow incomplete monitor |
| GMC | 2019 | Savana 2.8L (diesel, CA certified) | Exhaust Gas Sensor monitor incomplete | ECM diagnostic handling issue | ECM reflash per Recall N232408230, retest |
| GMC | 2022 | Sierra K2500 SLT 6.6L (diesel, CA certified) | Exhaust Gas Sensor monitor incomplete | Vehicle design anomaly | Test normally, OIS temporarily allows Exhaust Gas Sensor monitor incomplete |
| Hyundai | 2002 | Sonata | Readiness failure | Monitors difficult to complete | Run drive cycle, see TSB #02-36-030 |
| Hyundai | 2003 | Tiburon | No communication with generic OBD equipment | Pin 5 not grounded | Test normally on OIS, for generic OBD, recall #057, Hyundai TSB #03-01-003-01 |
| Infiniti | 2000 -2001 | I30 | Catalyst monitor failure | OEM scan tool only shows OBD catalyst code | Test catalyst, replace if defective |
| Infiniti | 2000 -2001 | I30 | Readiness failure | Monitors difficult to complete in normal driving | Run drive cycle |
| Isuzu | 1998-2005 | NPR (diesel, Federal certified, GVWR 10,001-14,000) | Not OBD II equipped | OBD not required in federal vehicles in this GVWR range | OIS skips OBD functional test |
| Isuzu | 2000-2002 | Hombre (2WD) 2.2L I-4 (E85) | Monitors don’t set on flex fuel models | System monitors disabled for >E15 blends | OIS ignores all 11 readiness monitors |
| Jaguar | 2017 | XE, XF, F-Pace 2.0L (diesel, CA certified, Test Group HJLXJ02.0STY) | NOx Aftertreatment System monitor incomplete | Vehicle design anomaly, Dealer recall H444 | Direct to Jaguar dealer for software update |
| Jaguar | 2018 | XE, XF, F-Pace & Rover Velar 2.0L (diesel, CA certified, Test group JJLXJ02.0STY) | NOx Aftertreatment System monitor incomplete | Vehicle design anomaly, Dealer recall H444 | Direct to Jaguar dealer for software update |
| Jaguar | 2019 | XE, XF, & F-Pace 2.0L (diesel, CA certified, Test group KJLXJ02.0STY) | NOx Aftertreatment System monitor incomplete | Vehicle design anomaly, Dealer recall H444 | Direct to Jaguar dealer for software update |
| Jeep | 2005-2006 | Wrangler | O2 sensor, O2 heater, catalyst monitors not ready | Vehicle design anomaly, TSB #25-005-13 Rev. A wiring mod | OIS allows incomplete O2 heater monitor |
| Jeep | 2010-2011 | Wrangler 3.8L | Oxygen sensor monitor failure | PCM monitor frequency issue, Recall L34/L35, OEM drive cycle issue | Reflash PCM per TSB 18-027-10, special drive cycle needed |
| Kia | 2009 | Borrego LX/EX 3.8L | Readiness failure, EGR monitor | EGR monitor difficult to complete, drive cycle issue | OIS allows EGR/VVT monitor incomplete |
| Land Rover | 2017 | Discovery, Range Rover, Range Rover Sport 3.0L (diesel, CA certified, Test group HJLXT03.0GTR) | NOx Aftertreatment System monitor incomplete | Vehicle design anomaly, Dealer recall N808 | Direct to Land Rover dealer for software update |
| Land Rover | 2018 | Velar 2.0L (diesel, CA certified, Test group JJLXJ02.0STY) | NOx Aftertreatment System monitor incomplete | Vehicle design anomaly, Dealer recall N808 | Direct to Land Rover dealer for software update |
| Land Rover | 2019 | Velar 2.0L (diesel, CA certified, Test group KJLXJ02.0STY) | NOx Aftertreatment System monitor incomplete | Vehicle design anomaly, Dealer recall N808 | Direct to Land Rover dealer for software update |
| Lexus | 2007 | RX400 Hybrid | Oxygen sensor (air/fuel) monitor readiness failure | Air Fuel monitor issue, AC monitor issue | Software update per Lexus campaign FLD, TSB #L-SB-0027-15, advise of recall |
| Lincoln | 2011 | MKX 3.5L & 3.7L | Readiness failure | OBD-II data clearing/VIN reporting issue | Consult Ford Emission Recall #13E04, ensure recall performed, complete drive cycles |
| Lincoln | 2020-2022 | Corsair (all engines, gasoline & hybrid) | No communication | Design issue, software update available | Direct to Ford dealer for software update, see SSM 50974 |
| Mazda | 2000 | MPV | Catalyst monitor failure | Catalyst/oxygen sensor issue | Diagnose, repair and retest |
| Mazda | 2002-2003 | B3000 (2WD) 3.0L V-6 (E-85) | Readiness monitors don’t set on flex fuel models | Monitors disabled for >E10 blends | OIS ignores all 11 readiness monitors |
| Mazda | 2003-2004 | Mazda 6 | False MIL illumination, U-code DTCs during OBDII test | PCM sensitive to OBD tool connection/disconnection | Reset monitors, connect/disconnect DAD key off, Mazda Service Bulletin #01-002/05 |
| Mazda | 2005 | Mazda 6 (2.3L only) | False MIL illumination, U-code DTCs during OBDII test | PCM sensitive to OBD tool connection/disconnection | Reset monitors, connect/disconnect DAD key off, Mazda Service Bulletin #01-002/05 |
| Mazda | 2003-2005 | Mazda 6 – 2.3L non PZEV, 3.0L | False MIL illumination | PCM sensitive to OBD tool connection/disconnection | Follow OIS prompts, connect/disconnect DAD key off, TSB #01-024/05, Recall TSB #1303F |
| Mitsubishi Fuso | 1998-2004 | FE639/FG639 (diesel, Federal certified, GVWR 10,001 –14,000) | Not OBDII equipped | OBD not required in federal vehicles in this GVWR range | OIS skips OBD functional test |
| Mitsubishi | 2000-2001 | Montero, Montero Sport, Diamante, 3000GT Mirage, Galant, Expo/Expo LRV, Eclipse (except 2.0L non-turbo 420A) | Readiness failure | Monitors difficult to complete | Follow recommended drive cycles, Mitsubishi service manual |
| Nissan | 1999-2007 | UD1200 (Diesel, Federal certified, GVWR 10,001-14,000) | Not OBDII equipped | OBD not required in federal vehicles in this GVWR range | OIS skips OBD functional test |
| Nissan | 2000-2001 | Maxima | Catalyst monitor failure | OEM scan tool only shows OBD catalyst code | Test catalyst, replace if defective |
| Nissan | 2000-2006 | All models | Readiness failure | Incomplete monitors in normal driving | Follow drive cycle for specific model, owner’s manual |
| Plymouth | 1999-2000 | Voyager 3.0L (built after 12/1/98) | EGR Monitor incomplete at high altitude | Reflash available | Reflash PCM per TSB 18-03-00, retest |
| Plymouth | 2000 | Voyager 3.3L V-6 (E-85) | Readiness monitors don’t set on flex fuel models | All monitors disabled for >E30 | OIS ignores all 11 readiness monitors |
| Suzuki | 2001 | Aerio | Readiness failure | Monitors difficult to complete | Follow drive cycle, OBD Clearinghouse, Suzuki service info |
| Suzuki | 2004 | Forenza | Readiness failure | Monitors difficult to complete | Follow drive cycle, OBD Clearinghouse, Suzuki service info |
| Toyota | 2000-2006 | All models | Readiness failure | Monitors difficult to complete | Follow drive cycle, Toyota service information |
| Toyota | 2003-2004 | 4 Runner | VSC light illuminates with aftermarket scan tool, CAN protocol | Stability control calibration loss | OIS won’t use CAN protocol |
| Toyota | 2007 | Highlander Hybrid | Oxygen sensor (air/fuel) monitor readiness failure | Air Fuel monitor issue | Software update per Toyota Special Service Campaign F0P, TSB #0042-15, advise of recall |
| Volvo | 2000 | S40 / V40 | Comprehensive, Oxygen sensor, Catalyst monitor failure | Defective ECM | Referee inspection if only these monitors unset, repair other failures first |
| Volvo | 2004-2006 | S40, V50 | Air conditioning readiness monitor mistakenly supported | Vehicle design anomaly | OIS ignores A/C monitor status |
| Volvo | 2005-2007 | XC90 | Air conditioning readiness monitor mistakenly supported | Vehicle design anomaly | OIS ignores A/C monitor status |
| VW | 2000-2005 | Passat | No OBD communication | Broken ground wire in ABS module | Repair per VW TSB #45 15 01, retest |
PDTC Vehicles of Interest: Addressing Persistent Diagnostic Codes
Certain vehicles are known to have issues with clearing Permanent Diagnostic Trouble Codes (PDTCs). In these cases, even after repairs, the PDTCs may persist, leading to unnecessary smog check failures. Inspection systems often ignore specific PDTCs on these vehicles to accommodate these known issues.
| Make | Year | Model & Engine | Issue | Cause & Remedy | Inspector Instruction |
|---|---|---|---|---|---|
| Audi | 2010 | Q7; 3.0 (TDI/diesel) | PDTCs P0087, P0088, P053F won’t clear | No remedy available | Test normally, OIS ignores these codes |
| Audi | 2011-2012 | Q7; 3.0 (TDI/diesel) | PDTCs P0087, P0088, P053F, P064A, P2635, P0230 won’t clear | No remedy available | Test normally, OIS ignores these codes |
| Chrysler | 2011-2015 | 200; 2.4, 3.6 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Chrysler | 2010-2014 | 300; 3.6, 5.7, 6.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Chrysler | 2017 | Pacifica Hybrid | Fails for PDTC C2200 or B22A9-00 | Reflash modules per TSB 08-005-21 and 08-006-21 | Reflash, retest |
| Chrysler | 2018 | Pacifica Hybrid | Fails for PDTC C2200 or B22A9-00 | Reflash modules per TSB 08-008-21 and 08-009-21 | Reflash, retest |
| Chrysler | 2019 | Pacifica Hybrid | Fails for PDTC C2200 or B22A9-00 | Reflash modules per TSB 08-011-21 and 08-012-21 | Reflash, retest |
| Chrysler | 2011-2015 | Town and Country; 3.6 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2011-2014 | Avenger | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2011-2012 | Caliber; 2.0, 2.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2011-2015 | Challenger; 3.6, 5.7, 6.4 | Fails for PDTC U0140 | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2011-2014 | Charger; 3.6, 5.7, 6.4 | Fails for PDTC U0140 | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2011-2015 | Grand Caravan; 3.6 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2010-2011 | Dakota; 3.7, 4.7 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2013 | Dart; 2.0 | Fails for PDTC U0140 | Reflash per Recall V50 and V51 | Reflash, retest |
| Dodge | 2013 | Dart; 2.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2014-2015 | Dart; 2.0, 2.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2011-2014 | Durango; 3.6, 5.7 | Fails for PDTC U0140 | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2011-2015 | Journey; 2.4, 3.6 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Dodge | 2010-2011 | Nitro; 3.7, 4.0 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Ford | 2011-2014 | Mustang; 3.7 & 5.0 (gasoline) | Fails for PDTC P0315 | Vehicle not self-clearing PDTC | Refer to Ford Customer Satisfaction Program 17N01 |
| Freightliner | 2014-2015 | Sprinter 2500 Sprinter 3500 (diesel) | Fails for PDTCs P202A, P203A, P208A, P20B9, P20BD, P20BE, P20FA | Vehicle not self-clearing PDTC | Test normally, OIS ignores these codes |
| Jeep | 2014-2015 | Cherokee; 2.4, 3.2 | Fails for PDTC U0140 | Reflash per Recall V51 | Reflash, retest |
| Jeep | 2010 | Commander; 5.7 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Jeep | 2010-2015 | Grand Cherokee; 3.6, 5.7, 6.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Jeep | 2014-2017 | Grand Cherokee (diesel) | Fails for PDTC P1D30 | Vehicle not self-clearing PDTC | Test normally, OIS ignores this code |
| Jeep | 2010-2012 | Liberty; 3.7 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Jeep | 2011-2015 | Patriot / Compass; 2.0, 2.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Jeep | 2010-2015 | Wrangler; 3.6, 3.8 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Mercedes | 2010-2013 | 350 Bluetec | Fails for PDTCs P203D, P20B6, P20BD, P20BE | Vehicle not self-clearing PDTC | Test normally, OIS ignores these codes |
| Mercedes | 2014-2015 | Sprinter 2500 Sprinter 3500 (diesel) | Fails for PDTCs P202A, P203A, P208A, P20B9, P20BD, P20BE, P20FA | Vehicle not self-clearing PDTC | Test normally, OIS ignores these codes |
| Ram | 2010-2014 | 1500; 3.6, 3.7, 4.7, 5.7 | Fails for PDTC U0140 | Reflash per Recall V51 | Reflash, retest |
| Ram | 2013 | 1500; 3.6, 5.7 | PDTCs won’t clear | Reflash per Recall V50 | Reflash, retest |
| Ram | 2014-2017 | 1500 (diesel) | Fails for PDTC P1D30 | Vehicle not self-clearing PDTC | Test normally, OIS ignores this code |
| Ram | 2010-2015 | 2500; 5.7, 6.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Ram | 2011-2015 | 3500 Cab Chassis; 5.7, 6.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Ram | 2013-2015 | 3500 Pickup; 5.7, 6.4 | PDTCs won’t clear | Reflash per Recall V51 | Reflash, retest |
| Ram | 2014 | Promaster; 3.6 | PDTCs won’t clear | Reflash per Recall V50 | Reflash, retest |
| Volkswagen | 2010 | Touareg; 3.0 (TDI/diesel) | PDTCs P20B5, P0087, P0088, P053F won’t clear | No remedy available | Test normally, OIS ignores these codes |
| Volkswagen | 2011-2012 | Touareg; 3.0 (TDI/diesel) | PDTCs P20B5, P0087, P0088, P053F, P064A, P2635, P0230 won’t clear | No remedy available | Test normally, OIS ignores these codes |
BAR-97 EIS Vehicles of Interest: Older Vehicle OBD Considerations
For vehicles model-year 1996-1999, which are tested using BAR-97 EIS (Emission Inspection System), there are also specific vehicle considerations related to monitor readiness. In many cases, the BAR-97 EIS is programmed to accommodate design anomalies in these older OBD systems.
| Make | Year | Model & Engine | Issue | Cause & Remedy | Inspector Instruction |
|---|---|---|---|---|---|
| BMW | 1996 | 7-Series, 8-Series 5.0L, 5.4L | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Chrysler | 1996 | Cirrus, Concord, LHS Sebring Convertible | Monitors reset to incomplete at key-off | Recall campaign #678, TSB #18-005-01 | Comply with recall, test normally |
| Chrysler | 1996 | Concord, LHS, New Yorker, Sebring, Town & Country 2.0L, 2.4L, 2.5L, 3.3L, 3.5L | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Chrysler | 1998-1999 | Town & Country 3.3L Flex Fuel | Monitors may not function with ethanol | Test normally | Test as normal |
| Dodge | 1996 | Stratus, Intrepid, Neon | Monitors reset to incomplete at key-off | Recall campaign #678, TSB #18-005-01 | Comply with recall, test normally |
| Dodge | 1996 | Avenger, Stratus 2.0L manual | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Dodge | 1996 | Stealth 3.0L | Monitors reset to incomplete at key-off | Not reflashable | EIS ignores readiness status |
| Dodge | 1998-1999 | Caravan 3.3L Flex Fuel | Monitors may not function with ethanol | Test normally | Test as normal |
| Eagle | 1996 | Vision | Monitors reset to incomplete at key-off | Recall campaign #678, TSB #18-005-01 | Comply with TSB, test normally |
| Eagle | 1996-1997 | Talon 2.0L | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Ford | 2020-2022 | F-53 Motorhome, F-59 Commercial Stripped Chassis (Gasoline not hybrid) | No OBD communication | Design issue, software update available | Direct to Ford dealer for software update, see SSM 50974 |
| Ford | 2021-2023 | F-650, F-750 (Gasoline not hybrid) | No OBD communication | Design issue, software update available | Direct to Ford dealer for software update, see SSM 50974 |
| Hyundai | 1996 | Accent 1.5L Elantra 1.8L Sonata 2.0L | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Hyundai | 1997-1998 | Sonata 2.0L, 3.0L | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| lnfiniti | 1996 | All models | Catalyst, evaporative monitors difficult | TSB #ITB98-011F, June 7, 2013 drive cycle | Test as normal |
| Kia | 1996 | Sephia Sportage | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Lexus | 1996-1999 | All models | Monitors difficult to complete | Lexus service info drive cycles | Test as normal |
| Mercedes-Benz | 1996 | C220, E320, C280, S320, SL320 | MIL illuminates with scan tool connection, no codes | OBD II connector RPM source issue | Connect OBD II only when prompted, use conventional RPM method |
| Mitsubishi | 1996-1997 | All Models | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Mitsubishi | 1998 | Eclipse (all), Galant 2.4L, Mirage, Montero Sport 2.4L | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Mitsubishi | 1998 | 3000GT, Diamante, Galant 2.3L, Montero, Montero Sport 3.0L | Monitors difficult to complete | Mitsubishi service manual drive cycles | Test as normal |
| Mitsubishi | 1999 | All models | Monitors difficult to complete | Mitsubishi service manual drive cycles | Test as normal |
| Nissan | 1996 | Sentra 1.6L, 2.0L manual, 200SX 1.6L, 240SX 2.4L, Maxima 3.0L, Pickup 2.4L | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Nissan | 1996-1997 | All models | Catalyst, evaporative monitors difficult | Nissan TSB #NTB98-018G, June 7, 2013 drive cycle | Comply with TSB, test normally |
| Nissan | 1999 | All models | Monitors difficult to complete | Owner’s manual drive cycle | Test as normal |
| Plymouth | 1996 | Breeze, Neon | Monitors reset to incomplete at key-off | Recall campaign #678, TSB #18-005-01 | Comply with recall, test normally |
| Plymouth | 1998-1999 | Voyager 3.3L Flex Fuel | Monitors may not function with ethanol | Test normally | Test as normal |
| Saab | 1996-1998 | 900 2.3L (B234 with Motronic 4.1) | Monitors difficult to complete | EIS ignores readiness status | Test normally |
| Saab | 1996-1998 | All models | Catalyst, evaporative monitors difficult | Saab Service Instruction No. 248-9037 drive cycle | Comply with TSB, test normally |
| Subaru | 1996 | All models | Readiness cleared at key-off | EIS ignores readiness status | Test normally |
| Toyota | 1996-1999 | All models | Monitors difficult to complete | Toyota service information drive cycles | Test as normal |
| Toyota | 1996-1997 | Tercel, Paseo | Evaporative monitor never completes/unsupported | EIS allows one incomplete monitor | Test as normal |
| VW | 1997-1999 | Passat | No OBD communication | Broken ground wire in ABS module | Repair per VW TSB #45 15 01, retest |
| Volvo | 1996-1998 | All models | Monitors difficult to complete | Service Bulletin 25-19 drive cycles | EIS ignores readiness status |
Conclusion: OBD2 Testing for Vehicle Health and Compliance
Understanding OBD2 test standards and being aware of vehicle-specific issues is crucial for both vehicle owners and automotive professionals. While OBD2 scanners like Cen-Tech OBD2 are powerful tools for diagnosing vehicle problems and reading vital data, it’s important to remember their primary function is diagnostics, not odometer manipulation. Focusing on proper vehicle maintenance, addressing fault codes promptly, and ensuring your vehicle meets emission standards are the true benefits of utilizing OBD2 technology. This guide provides a foundational understanding of OBD2 testing, helping you navigate smog checks, interpret diagnostic information, and keep your vehicle running smoothly and cleanly.
Disclaimer: This information is intended for general guidance and informational purposes only. Always consult official vehicle repair manuals, technical service bulletins, and certified technicians for specific diagnostic and repair procedures. Emission testing regulations and standards may vary by location, so always refer to your local authorities for the most up-to-date requirements.
