Is your check engine light illuminated in your 1990-1993 Honda Accord? Don’t worry, you can easily diagnose the issue yourself using the Accord’s built-in OBD1 system. This guide will walk you through the simple process of reading these diagnostic trouble codes (DTCs), helping you pinpoint the problem and take the first step towards fixing it. No need for expensive scan tools for these model years!
To retrieve the diagnostic codes from your 90-93 Honda Accord, follow these steps:
-
Locate the Service Connector: Begin by going to the passenger side of your vehicle. Look for the kick panel, the interior trim panel located near the passenger’s feet. Behind this panel, you will find a blue, 2-pin connector. This is the Service Check Connector (SCS) used to access the OBD1 system.
-
Prepare to Read Codes: Turn off your vehicle’s ignition. Using a paper clip, a piece of wire, or a dedicated connector, bridge the two terminals within the blue service connector. This essentially closes the circuit, allowing the ECU to output the diagnostic codes.
-
Initiate Code Reading: Insert your key into the ignition switch and turn it to the “ON” position (two clicks forward), just before starting the engine. Do not start the car.
-
Observe the Check Engine Light: Carefully watch the check engine light (CEL) on your dashboard. It will now begin to blink in a pattern. These blinks are how the OBD1 system communicates the diagnostic trouble codes.
-
Interpreting the Blink Codes: The check engine light will blink long and short flashes. A long blink represents 10, and a short blink represents 1. The codes are outputted as a series of blinks. For example, two long blinks followed by three short blinks would indicate code 23. The entire sequence of codes will repeat, so pay attention and count carefully. It’s helpful to write down the codes as they are displayed to avoid confusion.
-
Consult the OBD1 Code List: Once you have noted the blink codes, compare them against the following list of OBD1 codes for 1990-1993 Honda Accords. This list details the potential issue associated with each code, helping you understand what system or sensor might be malfunctioning.
Honda Accord 1990-1993 OBD1 Trouble Codes:
| Code | Description |
|---|---|
| 1 | O2A – Oxygen sensor #1 |
| 2 | O2B – Oxygen sensor #2 |
| 3 | MAP – Manifold Absolute Pressure Sensor |
| 4 | CKP – Crank Position Sensor |
| 5 | MAP – Manifold Absolute Pressure Sensor (Redundant) |
| 6 | ECT – Engine Coolant Temperature Sensor |
| 7 | TPS – Throttle Position Sensor |
| 8 | TDC – Top Dead Centre Sensor |
| 9 | CYP – Cylinder Sensor |
| 10 | IAT – Intake Air Temperature Sensor |
| 12 | EGR – Exhaust Gas Recirculation Lift Valve |
| 13 | BARO – Atmospheric Pressure Sensor |
| 14 | IAC (EACV) – Idle Air Control Valve |
| 15 | Ignition Output Signal |
| 16 | Fuel Injectors |
| 17 | VSS – Vehicle Speed Sensor |
| 19 | Automatic Transmission Lockup Control Valve |
| 20 | Electrical Load Detector |
| 21 | VTEC Spool Solenoid Valve |
| 22 | VTEC Pressure Valve |
| 23 | Knock Sensor |
| 30 | Automatic Transmission A Signal |
| 31 | Automatic Transmission B Signal |
| 36 | Traction Control (JDM ECU) |
| 41 | Primary Oxygen Sensor Heater |
| 43 | Fuel Supply System |
| 45 | Fuel System Too Rich or Lean |
| 48 | LAF – Lean Air Fuel Sensor |
| 54 | CKF – Crank Fluctuation Sensor |
| 58 | TDC Sensor #2 |
| 61 | Primary Oxygen Sensor |
| 63 | Secondary Oxygen Sensor |
| 65 | Secondary Oxygen Sensor Heater |
| 71 | Random Misfire Cylinder 1 |
| 72 | Random Misfire Cylinder 2 |
| 73 | Random Misfire Cylinder 3 |
| 74 | Random Misfire Cylinder 4 |
| 80 | Exhaust Gas Recirculation Insufficient Flow |
| 86 | ECT Sensor Range/Performance Problem |
| 90 | Evaporative Emission Control System Leak |
| 91 | Fuel Tank Pressure Sensor Low Input |
| 92 | Evaporative Emission Control System Purge Flow |
TCU Codes (Transmission Control Unit):
| Code | Description |
|---|---|
| 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. |
| 4 | Vehicle Speed Sensor open or shorted – No speedometer signal. |
| 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 speed pulse generator open or shorted. |
| 10 | Coolant Temperature Sensor open or shorted. |
| 11 | Engine RPM (Ignition coil signal) open or shorted. |
| 13 | Main shaft speed pulse generator open or shorted. |
| 14 | Linear (line pressure control) solenoid open or shorted. |
| 15 | Kick down switch circuit shorted. |
Resetting the ECU (Engine Control Unit):
After addressing the issue indicated by the trouble code, or if you simply want to reset the system after repairs, you can reset your Honda Accord’s ECU. This will clear the check engine light.
-
Disconnect Battery Negative Terminal: Ensure the ignition is OFF. Locate the negative battery terminal (usually black and marked with a “-“). Loosen the nut on the terminal clamp and carefully disconnect the cable. It’s crucial to disconnect the negative terminal first to prevent accidental shorts.
-
Remove Hazard Fuse: Open the under-hood fuse box. Locate and remove the “Hazard” fuse. This step further ensures complete power drain from the ECU.
-
Wait: Allow the vehicle to sit for approximately 10-15 minutes. This gives the ECU sufficient time to fully discharge and reset its memory.
-
Reinstall Fuse and Battery Terminal: Reinstall the “Hazard” fuse back into the fuse box. Reconnect the negative battery terminal, ensuring it is securely tightened.
-
Restart and Idle: Start your Honda Accord without any accessories turned on (radio, lights, A/C). Let the engine idle for a few minutes. This allows the ECU to relearn basic engine parameters.
-
Verify Reset: Turn off the engine and then restart it normally. The check engine light should now be off, indicating a successful ECU reset.
By following these steps, you can effectively diagnose and address check engine light issues in your 1990-1993 Honda Accord using its OBD1 system. Remember that this guide is for informational purposes, and complex issues may require professional diagnosis and repair.
