Navigating car troubles can be stressful, especially when that ominous “Check Engine Light” (CEL) illuminates on your Honda’s dashboard. This light is your vehicle’s way of communicating that something isn’t working as it should. Modern Honda and Acura vehicles utilize an On-Board Diagnostics system, specifically OBD2, to monitor various components and systems. When a fault is detected, the system logs a Diagnostic Trouble Code (DTC), also known as a CEL code. Understanding these codes is the first step towards diagnosing and resolving the issue, potentially saving you time and money on unnecessary repairs.
This guide provides a comprehensive list of OBD2 CEL codes for Honda vehicles, alongside some OBD0 and OBD1 codes for older models, to help you understand what your check engine light is trying to tell you. While this list is extensive, remember that diagnosing car problems can be complex. This information is for informational purposes and should be used as a starting point for troubleshooting.
Understanding OBD2 and CELs in Your Honda
The introduction of OBD2 (On-Board Diagnostics II) in the mid-1990s standardized vehicle diagnostics across the automotive industry. For Honda and Acura vehicles, OBD2 provides a wealth of information about your car’s health. When your Honda’s computer, also known as the Engine Control Unit (ECU), detects a problem outside of normal operating parameters, it triggers the check engine light and stores a corresponding DTC.
These DTCs are designed to pinpoint the general area of the problem. Using an OBD2 scanner, readily available online or at most auto parts stores, you can retrieve these codes and begin to understand the potential issue. It’s important to note that a CEL code provides a starting point for diagnosis, not necessarily the definitive answer. Further investigation and testing are often required to accurately identify the root cause and perform the correct repair.
Comprehensive List of OBD & OBD2 CEL Codes for Honda and Acura Vehicles
Below is a detailed list of OBD0, OBD1, and OBD2 codes relevant to Honda and Acura vehicles. Please note that while OBD2 is the current standard, understanding older OBD systems can be helpful for owners of classic Hondas.
OBD 0/1/2 Engine CEL Codes:
- 0 – ECU: Faulty ECU or ECU ROM. This indicates a problem with the vehicle’s computer itself. Further diagnosis of the ECU is required.
- 1 – O2A: Oxygen sensor #1. This code refers to the primary oxygen sensor, usually located before the catalytic converter.
- 2 – O2B: Oxygen sensor #2. This code points to the secondary oxygen sensor, typically positioned after the catalytic converter.
- 3 – MAP: Manifold Absolute Pressure Sensor. A fault with the MAP sensor, which measures air pressure in the intake manifold.
- 4 – CKP: Crank Position Sensor. Indicates an issue with the crankshaft position sensor, crucial for ignition timing and fuel delivery.
- 5 – MAP: Manifold Absolute Pressure Sensor (Duplicate code, likely an error in original list, could indicate different MAP sensor related issue depending on context).
- 6 – ECT: Engine Coolant Temperature Sensor. Problem with the sensor that monitors engine coolant temperature.
- 7 – TPS: Throttle Position Sensor. Faulty throttle position sensor, which measures the throttle valve angle.
- 8 – TDC: Top Dead Center Sensor. Issue with the TDC sensor, related to crankshaft position and timing.
- 9 – CYP: Cylinder Sensor. Problem with the cylinder position sensor, used for misfire detection and cylinder identification.
- 10 – IAT: Intake Air Temperature Sensor. Faulty intake air temperature sensor, measuring the temperature of incoming air.
- 11 – Engine Overheating: Indicates the engine is overheating, often due to cooling system problems.
- 12 – EGR: Exhaust Gas Recirculation Lift Valve. Problem with the EGR valve or system, related to emissions control.
- 13 – BARO: Barometric Pressure Sensor. Faulty barometric pressure sensor, measuring atmospheric pressure.
- 14 – IAC (EACV): Idle Air Control Valve (Electronic Air Control Valve). Issue with the IAC valve, controlling idle speed.
- 15 – Ignition Output Signal: Problem with the ignition output signal from the ECU.
- 16 – Fuel Injectors: Faulty fuel injector or injector circuit.
- 17 – VSS: Vehicle Speed Sensor. Issue with the vehicle speed sensor, affecting speedometer and potentially transmission operation.
- 19 – Automatic Transmission Lockup Control Valve: Problem with the automatic transmission lockup control valve.
- 20 – ELD: Electrical Load Detector. Faulty electrical load detector, monitoring electrical system load.
- 21 – VTEC Spool Solenoid Valve: Issue with the VTEC (Variable Valve Timing and Lift Electronic Control) spool solenoid valve.
- 22 – VTEC Pressure Valve: Problem with the VTEC pressure valve.
- 23 – Knock Sensor: Faulty knock sensor, detecting engine knock or detonation.
- 30 – Automatic Transmission A Signal: Problem with automatic transmission signal A.
- 31 – Automatic Transmission B Signal: Problem with automatic transmission signal B.
- 36 – Traction Control: Traction control system fault (found on some JDM ECUs).
- 38 – Secondary VTEC Solenoid: Secondary VTEC solenoid issue (on JDM 3-stage D15B VTEC ECUs – P2J).
- 41 – Primary Oxygen Sensor Heater: Problem with the heater circuit for the primary oxygen sensor.
- 43 – Fuel Supply System: Issue with the fuel supply system, potentially fuel pump, filter, or pressure regulator.
- 45 – Fuel System Too Rich or Lean: Indicates the fuel system is delivering too much or too little fuel.
- 48 – LAF: Lean Air Fuel Sensor. Fault with the lean air-fuel ratio sensor.
- 54 – CKF: Crank Fluctuation Sensor. Problem with the crank fluctuation sensor, related to misfire detection.
- 58 – TDC Sensor #2: Issue with a secondary top dead center sensor (if applicable).
- 61 – Primary Oxygen Sensor: Primary oxygen sensor circuit issue (similar to code 1, may indicate circuit problem rather than sensor failure itself).
- 63 – Secondary Oxygen Sensor Circuit: Secondary oxygen sensor circuit problem (similar to code 2, may indicate circuit issue).
- 65 – Secondary Oxygen Sensor Heater Wire: Fault in the secondary oxygen sensor heater wire circuit.
- 67 – Catalytic Converter: Catalytic converter efficiency below threshold.
- 71 – Random Misfire Cylinder 1: Random misfire detected in cylinder 1.
- 72 – Random Misfire Cylinder 2: Random misfire detected in cylinder 2.
- 73 – Random Misfire Cylinder 3: Random misfire detected in cylinder 3.
- 74 – Random Misfire Cylinder 4: Random misfire detected in cylinder 4.
- 80 – EGR Valve/Line: Problem with the EGR valve or EGR line, potentially blockage or leak.
- 86 – ECT Sensor – Cooling System: Engine Coolant Temperature sensor issue specifically related to the cooling system (similar to code 6, may be more specific context).
- 91 – Fuel Tank Pressure Sensor: Faulty fuel tank pressure sensor, part of the EVAP system.
- 92 – EVAP Solenoid/Valve/Vacuum Lines: Problem within the EVAP (Evaporative Emission Control System), potentially solenoid, valve or vacuum lines.
OBD1 TCU (Transmission Control Unit) Codes:
These codes are specific to Honda vehicles equipped with OBD1 Transmission Control Units (TCUs).
- 1 – Lock-up Solenoid ‘A’ Circuit: Lock-up solenoid ‘A’ circuit open or shorted.
- 2 – Lock-up Solenoid ‘B’ Circuit: Lock-up solenoid ‘B’ circuit open or shorted.
- 3 – Throttle Position Sensor Circuit: Throttle Position Sensor circuit open or shorted (Transmission related).
- 4 – Vehicle Speed Sensor: Vehicle Speed Sensor open or shorted – No signal from speedometer (Transmission related).
- 5 – Shift Lever Position Switch Circuit: Shift Lever Position Switch circuit shorted.
- 6 – Shift Lever Position Switch Circuit: Shift Lever Position Switch circuit open.
- 7 – Shift Solenoid ‘A’ Circuit: Shift Solenoid ‘A’ circuit open or shorted.
- 8 – Shift Solenoid ‘B’ Circuit: Shift Solenoid ‘B’ circuit open or shorted.
- 9 – Counter Shaft Speed Pulse Generator: Counter shaft or transmission speed pulse generator open or shorted.
- 10 – Coolant Temperature Sensor: Coolant Temperature Sensor open or shorted (Transmission related).
- 11 – Engine RPM (Ignition Coil Signal): Engine RPM (Ignition coil signal) open or shorted (Transmission related).
- 13 – Main Shaft Speed Pulse Generator: Main shaft speed pulse generator open or shorted.
- 14 – Linear (Line Pressure Control) Solenoid: Linear (line pressure control) solenoid open or shorted.
- 15 – Kick Down Switch Circuit: Kick down switch circuit shorted.
Conclusion: Taking the Next Steps After Reading Honda CEL Codes
This comprehensive list of CEL codes for Honda vehicles is a valuable resource for understanding potential issues indicated by your check engine light. Once you have retrieved the code from your OBD2 scanner and consulted this list, remember that this is just the beginning of the diagnostic process.
For accurate diagnosis and repair, it’s recommended to consult a qualified mechanic or technician. They possess the expertise, specialized tools, and diagnostic procedures to pinpoint the exact cause of the problem and perform the necessary repairs. Using this code list in conjunction with professional advice will help you get your Honda back on the road safely and efficiently.
