Honda OBD2 Check Engine Light Codes: Your Comprehensive Guide to Understanding and Troubleshooting

The check engine light in your Honda is often the first indicator that something is amiss. Modern Honda vehicles, like most cars on the road today, utilize an On-Board Diagnostics system, specifically OBD2, to monitor various systems and components. When the system detects a problem that could affect emissions or vehicle operation, it illuminates the check engine light and stores a corresponding diagnostic trouble code (DTC). These codes can be accessed using an OBD2 scanner and are crucial for diagnosing and resolving the issue.

This comprehensive guide provides a detailed list of Honda Obd2 Check Engine Light Codes, helping you understand what each code signifies and directing you towards effective troubleshooting. Understanding these codes is the first step in maintaining your Honda’s health and performance.

Decoding Your Honda Check Engine Light: OBD2 Codes Explained

OBD2 codes are standardized across the automotive industry, but knowing Honda-specific codes can streamline your diagnostic process. The codes listed below cover a wide range of potential issues, from sensor malfunctions to engine and transmission problems.

It’s important to note that a check engine light can be triggered by something as minor as a loose gas cap or a more serious issue like a catalytic converter failure. Therefore, retrieving the specific code with an OBD2 scanner is always the recommended first step.

Honda OBD Code List (OBD 0/1/2 CEL Codes)

Here’s a breakdown of common OBD codes you might encounter in your Honda or Acura vehicle. These codes are generally consistent across OBD0, OBD1, and OBD2 systems unless specified otherwise.

• 0 – ECU – Faulty Engine Control Unit or ECU Read-Only Memory (ROM). This indicates a problem with the car’s computer itself.
• 1 – O2A – Oxygen Sensor #1 Malfunction. This sensor is crucial for air/fuel mixture monitoring.
• 2 – O2B – Oxygen Sensor #2 Malfunction. Often related to catalytic converter efficiency monitoring.
• 3 – MAP – Manifold Absolute Pressure Sensor Circuit Malfunction. Affects air intake measurement and fuel delivery.
• 4 – CKP – Crankshaft Position Sensor Circuit Malfunction. Essential for ignition timing and engine synchronization.
• 5 – MAP – Manifold Absolute Pressure Sensor Circuit Malfunction (Redundant Code).
• 6 – ECT – Engine Coolant Temperature Sensor Circuit Malfunction. Impacts fuel mixture and engine cooling fan operation.
• 7 – TPS – Throttle Position Sensor Circuit Malfunction. Relates to accelerator pedal input and engine response.
• 8 – TDC – Top Dead Center Sensor Circuit Malfunction. Used for precise engine timing.
• 9 – CYP – Cylinder Position Sensor Circuit Malfunction. Helps identify cylinder firing order.
• 10 – IAT – Intake Air Temperature Sensor Circuit Malfunction. Measures intake air temperature for fuel adjustments.
• 11 – Engine Overheating. Indicates a serious cooling system issue requiring immediate attention.
• 12 – EGR – Exhaust Gas Recirculation Lift Valve Malfunction. Affects emissions control and engine efficiency.
• 13 – BARO – Barometric Pressure Sensor Circuit Malfunction. Measures atmospheric pressure for altitude adjustments.
• 14 – IAC (EACV) – Idle Air Control Valve Malfunction. Controls engine idle speed.
• 15 – Ignition Output Signal Malfunction. Problem with the ignition system’s control signal.
• 16 – Fuel Injector Circuit Malfunction. Issues with fuel delivery to the cylinders.
• 17 – VSS – Vehicle Speed Sensor Circuit Malfunction. Affects speedometer and transmission operation.
• 19 – Automatic Transmission Lockup Control Valve Malfunction. (Automatic Transmissions)
• 20 – ELD – Electrical Load Detector Circuit Malfunction. Monitors electrical system load.
• 21 – VTEC Spool Solenoid Valve Malfunction. (VTEC Engines) Relates to variable valve timing system.
• 22 – VTEC Pressure Valve Malfunction. (VTEC Engines) Pressure issue within the VTEC system.
• 23 – Knock Sensor Circuit Malfunction. Detects engine knocking or detonation.
• 30 – Automatic Transmission A Signal Malfunction. (Automatic Transmissions)
• 31 – Automatic Transmission B Signal Malfunction. (Automatic Transmissions)
• 36 – Traction Control System Malfunction. (Specific JDM ECUs)
• 38 – Secondary VTEC Solenoid Malfunction. (JDM 3-Stage D15B VTEC ECUs – P2J)
• 41 – Primary Oxygen Sensor Heater Circuit Malfunction. Heater for the primary O2 sensor.
• 43 – Fuel Supply System Malfunction. General fuel delivery problem.
• 45 – Fuel System Too Rich or Lean. Air/fuel mixture imbalance.
• 48 – LAF – Lean Air Fuel Sensor Circuit Malfunction. Advanced type of oxygen sensor.
• 54 – CKF – Crankshaft Fluctuation Sensor Circuit Malfunction. Refined crank position sensing.
• 58 – TDC Sensor #2 Circuit Malfunction. Secondary top dead center sensor issue.
• 61 – Primary Oxygen Sensor Circuit Malfunction. (Redundant Code, similar to code 1)
• 63 – Secondary Oxygen Sensor Circuit Malfunction. (Redundant Code, similar to code 2)
• 65 – Secondary Oxygen Sensor Heater Wire Malfunction. Heater for the secondary O2 sensor.
• 67 – Catalytic Converter Efficiency Below Threshold. Indicates a failing catalytic converter.
• 71 – Random Misfire Detected – Cylinder 1. Misfire in cylinder number 1.
• 72 – Random Misfire Detected – Cylinder 2. Misfire in cylinder number 2.
• 73 – Random Misfire Detected – Cylinder 3. Misfire in cylinder number 3.
• 74 – Random Misfire Detected – Cylinder 4. Misfire in cylinder number 4.
• 80 – EGR Valve/Line Malfunction. EGR system issue.
• 86 – ECT Sensor – Cooling System Malfunction. (Redundant Code, similar to code 6)
• 91 – Fuel Tank Pressure Sensor Circuit Malfunction. EVAP system related.
• 92 – EVAP Solenoid/Valve/Vacuum Lines Malfunction. Evaporative Emission Control System problem.

Honda OBD1 TCU Codes (Transmission Control Unit)

These codes are specific to Honda vehicles equipped with OBD1 Transmission Control Units (TCUs) and relate to automatic transmission issues.

• 1 – Lock-up Solenoid ‘A’ Circuit Open or Shorted.
• 2 – Lock-up Solenoid ‘B’ Circuit Open or Shorted.
• 3 – Throttle Position Sensor Circuit Open or Shorted. (Transmission related TPS issue)
• 4 – Vehicle Speed Sensor Open or Shorted – No signal from speedometer. (Transmission related VSS issue)
• 5 – Shift Lever Position Switch Circuit Shorted.
• 6 – Shift Lever Position Switch Circuit Open.
• 7 – Shift Solenoid ‘A’ Circuit Open or Shorted.
• 8 – Shift Solenoid ‘B’ Circuit Open or Shorted.
• 9 – Counter shaft or transmission speed pulse generator open or shorted.
• 10 – Coolant Temperature Sensor Open or Shorted. (Transmission related CTS issue)
• 11 – Engine RPM (Ignition coil signal) Open or Shorted. (Transmission RPM signal issue)
• 13 – Main shaft speed pulse generator open or shorted.
• 14 – Linear (line pressure control) solenoid open or shorted.
• 15 – Kick down switch circuit shorted.

What to Do When Your Honda Check Engine Light Comes On

1. Retrieve the OBD2 Code: Use an OBD2 scanner to read the stored diagnostic code(s). These scanners are readily available online or at auto parts stores.
2. Consult This Code List: Locate your code in the lists above to understand the potential issue.
3. Further Diagnosis: The code provides a starting point. Further diagnosis may be required to pinpoint the exact cause, which could involve checking wiring, sensors, or other components.
4. Seek Professional Help: If you are not comfortable diagnosing and repairing the issue yourself, it’s always best to consult a qualified mechanic. Especially for complex codes or persistent issues, professional diagnosis and repair are recommended.

This guide is intended to provide helpful information for understanding Honda OBD2 check engine light codes. Always prioritize safety and consult professional resources when performing vehicle maintenance and repairs.