Decoding your Honda’s check engine light (CEL) can feel like deciphering a secret language. When that light illuminates on your dashboard, it’s your car’s way of telling you something needs attention. Fortunately, modern Honda vehicles, like many others, utilize an On-Board Diagnostics system, specifically OBD2, to pinpoint potential problems. Understanding Honda Cel Codes Obd2 is the first step to diagnosing and resolving these issues, saving you time and potentially costly repairs.
This guide provides a comprehensive list of Honda OBD2 CEL codes to help you understand what your check engine light is trying to communicate. Whether you own a classic Acura or a modern Honda model, this code list will serve as a valuable resource for preliminary diagnosis.
Honda OBD2 & Related CEL Codes:
Here’s a breakdown of common Honda CEL codes. Note that while the focus is OBD2, this list includes codes that might appear in older OBD0 and OBD1 Honda systems as well, as the underlying issues can be similar.
- 0 – ECU – Faulty ECU or ECU ROM: Indicates a problem with the Engine Control Unit itself. This is the brain of your car’s engine management system and requires careful diagnosis.
- 1 – O2A – Oxygen sensor #1: Points to a malfunction in the primary oxygen sensor, usually located before the catalytic converter. This sensor is crucial for air-fuel mixture monitoring.
- 2 – O2B – Oxygen sensor #2: Indicates an issue with the secondary oxygen sensor, typically located after the catalytic converter. This sensor monitors catalytic converter efficiency.
- 3 – MAP – Manifold Absolute Pressure Sensor: Signifies a problem with the MAP sensor, which measures air pressure in the intake manifold, essential for calculating air density and fuel delivery.
- 4 – CKP – Crank Position Sensor: A fault code for the Crankshaft Position Sensor. This sensor tracks the crankshaft’s position and speed, critical for ignition timing and fuel injection.
- 5 – MAP – Manifold Absolute Pressure Sensor: (Duplicate code, likely same as code 3, re-emphasizing MAP sensor issues)
- 6 – ECT – Water Temperature Sensor: Indicates a problem with the Engine Coolant Temperature sensor. This sensor monitors engine temperature to prevent overheating and optimize engine performance.
- 7 – TPS – Throttle Position Sensor: Signifies a malfunction in the Throttle Position Sensor. This sensor measures the throttle valve’s angle, crucial for determining engine load and driver demand.
- 8 – TDC – Top Dead Center Sensor: A fault code for the Top Dead Center sensor, which helps determine the top dead center position of the pistons, important for ignition and injection timing.
- 9 – CYP – Cylinder Sensor: Indicates a problem with the Cylinder Position Sensor, which helps identify which cylinder is firing.
- 10 – IAT – Intake Air Temperature Sensor: Signifies a malfunction in the Intake Air Temperature sensor. This sensor measures the temperature of the air entering the engine, affecting air density calculations.
- 11 – Engine Overheating: A general code indicating the engine is overheating. This could be due to various issues in the cooling system.
- 12 – EGR – Exhaust Gas Recirculation Lift Valve: Points to a problem with the Exhaust Gas Recirculation system, specifically the lift valve. The EGR system reduces NOx emissions.
- 13 – BARO – Atmospheric Pressure Sensor: Indicates a fault with the Barometric Pressure sensor, which measures atmospheric pressure, used for altitude compensation in fuel and ignition calculations.
- 14 – IAC (EACV) – Idle Air Control Valve: Signifies a problem with the Idle Air Control valve (also known as Electronic Air Control Valve). This valve regulates idle speed.
- 15 – Ignition Output Signal: A general code related to the ignition system output signal, requiring further investigation into ignition components.
- 16 – Fuel Injectors: Indicates a problem with the fuel injectors. This could be a general injector circuit issue or a problem with specific injectors.
- 17 – VSS – Vehicle Speed Sensor: Signifies a malfunction in the Vehicle Speed Sensor. This sensor provides speed information to the ECU and other vehicle systems.
- 19 – Automatic Transmission Lockup Control Valve: Relates to the automatic transmission lockup control valve, affecting torque converter lockup and fuel efficiency.
- 20 – ELD – Electrical Load Detector: Indicates a problem with the Electrical Load Detector. This sensor monitors the electrical load on the charging system.
- 21 – VTEC Spool Solenoid Valve: Points to an issue with the VTEC (Variable Valve Timing and Lift Electronic Control) spool solenoid valve, affecting VTEC engagement.
- 22 – VTEC Pressure Valve: Indicates a problem with the VTEC pressure valve, also related to the VTEC system’s hydraulic control.
- 23 – Knock Sensor: Signifies a malfunction in the Knock Sensor, which detects engine knocking or detonation.
- 30 – Automatic Transmission A Signal: A general code related to the automatic transmission ‘A’ signal, requiring further diagnosis of transmission control systems.
- 31 – Automatic Transmission B Signal: Similar to code 30, but related to the automatic transmission ‘B’ signal.
- 36 – Traction Control (JDM ECU): Specific to some Japanese Domestic Market (JDM) ECUs, indicating a traction control system issue.
- 38 – Secondary VTEC Solenoid (JDM D15B Vtec ECU): Specific to JDM 3-stage D15B Vtec ECUs (P2J), indicating a problem with the secondary VTEC solenoid.
- 41 – Primary Oxygen Sensor Heater: Indicates a problem with the heater circuit of the primary oxygen sensor, which is needed for the sensor to reach operating temperature quickly.
- 43 – Fuel Supply System: A general code indicating a problem with the fuel supply system, which could involve fuel pressure, pump, or filter issues.
- 45 – Fuel System Too Rich or Lean: Signifies that the fuel system is delivering an improper air-fuel mixture, either too rich (too much fuel) or too lean (too little fuel).
- 48 – LAF – Lean Air Fuel Sensor: Indicates a problem with the Lean Air Fuel sensor, a type of wideband oxygen sensor used for precise air-fuel ratio control.
- 54 – CKF – Crank Fluctuation Sensor: A fault code for the Crank Fluctuation Sensor, which is related to crankshaft speed variations and misfire detection.
- 58 – TDC Sensor #2: Indicates a problem with a secondary Top Dead Center sensor, if equipped.
- 61 – Primary Oxygen Sensor: (Likely redundant, same as code 1, re-emphasizing primary O2 sensor issues)
- 63 – Secondary Oxygen Sensor Circuit: Indicates a circuit problem with the secondary oxygen sensor, possibly wiring or connector issues.
- 65 – Secondary Oxygen Sensor Heater Wire: Specifically points to a problem with the heater wire of the secondary oxygen sensor.
- 67 – Catalytic Converter Efficiency Low: Indicates that the catalytic converter is not functioning efficiently in reducing emissions.
- 71 – Random Misfire Cylinder 1: Indicates random misfires detected in cylinder 1. Misfires occur when combustion is incomplete or absent in a cylinder.
- 72 – Random Misfire Cylinder 2: Random misfires detected in cylinder 2.
- 73 – Random Misfire Cylinder 3: Random misfires detected in cylinder 3.
- 74 – Random Misfire Cylinder 4: Random misfires detected in cylinder 4.
- 80 – EGR Valve/Line: A more general EGR system code, possibly indicating issues with the valve or EGR lines (vacuum or coolant lines).
- 86 – ECT Sensor – Cooling System: (Likely redundant, same as code 6, re-emphasizing ECT sensor/Cooling System issues)
- 91 – Fuel Tank Pressure Sensor: Indicates a problem with the Fuel Tank Pressure sensor, part of the EVAP (Evaporative Emission Control) system.
- 92 – EVAP Solenoid/Valve/Vacuum Lines: A general EVAP system code, indicating issues with the EVAP solenoid, valve, or vacuum lines.
OBD1 TCU Codes (Transmission Control Unit):
These codes are specifically for Honda vehicles with OBD1 Transmission Control Units.
- 1 – Lock-up Solenoid ‘A’ circuit open or shorted: Indicates an electrical issue with the ‘A’ lock-up solenoid circuit in the automatic transmission.
- 2 – Lock-up Solenoid ‘B’ circuit open or shorted: Indicates an electrical issue with the ‘B’ lock-up solenoid circuit.
- 3 – Throttle Position Sensor circuit open or shorted: An electrical issue with the TPS circuit as it relates to the transmission control.
- 4 – Vehicle Speed Sensor open or shorted – No signal from speedometer: Electrical issue with the VSS circuit affecting transmission control, possibly also impacting the speedometer.
- 5 – Shift Lever Position Switch circuit shorted: Short circuit in the Shift Lever Position Switch circuit.
- 6 – Shift Lever Position Switch circuit open: Open circuit in the Shift Lever Position Switch circuit.
- 7 – Shift Solenoid ‘A’ circuit open or shorted: Electrical issue with the ‘A’ shift solenoid circuit in the automatic transmission.
- 8 – Shift Solenoid ‘B’ circuit open or shorted: Electrical issue with the ‘B’ shift solenoid circuit.
- 9 – Counter shaft or transmission speed pulse generator open or shorted: Electrical issue with the counter shaft speed sensor circuit.
- 10 – Coolant Temperature Sensor open or shorted: Electrical issue with the Coolant Temperature Sensor circuit as it relates to transmission control.
- 11 – Engine RPM (Ignition coil signal) open or shorted: Electrical issue with the engine RPM signal circuit affecting transmission control.
- 13 – Main shaft speed pulse generator open or shorted: Electrical issue with the main shaft speed sensor circuit.
- 14 – Linear (line pressure control) solenoid open or shorted: Electrical issue with the linear solenoid circuit, which controls transmission line pressure.
- 15 – Kick down switch circuit shorted: Short circuit in the kick-down switch circuit.
Conclusion:
This comprehensive list of Honda CEL codes OBD2 and related codes provides a starting point for diagnosing your Honda or Acura’s check engine light. Remember that this list is for informational purposes and professional diagnosis is always recommended. Using an OBD2 scanner to read the specific code from your vehicle is the first step. This guide will then help you understand the potential issue and inform your next steps in troubleshooting and repair, ensuring your Honda runs smoothly and efficiently.
