Is your check engine light illuminated in your 1990-1993 Honda Accord? Diagnosing the issue might seem daunting, but with the right knowledge, you can easily understand what your car is trying to tell you. These model years of the Honda Accord utilize an OBD1 system, which, while different from the more modern OBD2, is still straightforward to read and interpret fault codes. This guide will walk you through the process of accessing and understanding these OBD1 codes on your 90-93 Accord, helping you pinpoint potential problems and take informed steps towards repair.
Accessing OBD1 Trouble Codes on Your 90-93 Honda Accord
Unlike newer vehicles that require a scan tool to read diagnostic codes, the 1990-1993 Honda Accord uses a simple blink code system. This ingenious method allows you to retrieve trouble codes using just a paper clip or a piece of wire. Here’s how to do it:
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Locate the Service Connector: Begin by finding the blue, 2-wire service connector. This connector is typically located in the passenger side kick panel. You’ll need to remove the kick panel to access it.
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Prepare to Bridge the Connector: Once you’ve located the blue connector, take your paper clip, wire, or connector and prepare to bridge the two terminals within it.
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Turn the Ignition to ‘ON’: Insert your key into the ignition switch and turn it two clicks to the ‘ON’ position. This is the position where all the dashboard lights illuminate, but you do not start the engine.
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Observe the Check Engine Light: Now, carefully watch the check engine light (CEL) on your dashboard. It will begin to blink in a pattern. This pattern represents the diagnostic trouble codes.
Understanding OBD1 Blink Codes
The OBD1 system on your 90-93 Honda Accord uses a series of long and short blinks to communicate fault codes. Here’s how to interpret them:
- Long Blink: A long blink of the CEL represents 10.
- Short Blink: A short blink represents 1.
The codes are presented as a combination of long and short blinks. For example, one long blink followed by two short blinks would indicate code 12. The system will cycle through all stored codes, repeating the sequence until you turn the ignition off. It’s crucial to note down all the codes as they are displayed.
OBD1 Trouble Code List for 90-93 Honda Accord
Once you have retrieved the blink codes, you’ll need to compare them against a code list to understand what they mean. Here’s a comprehensive list of OBD1 trouble codes for the 1990-1993 Honda Accord:
Engine (ECU) 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 |
| 6 | ECT – Water 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 Detected |
| 86 | ECT Sensor (Engine Coolant Temperature) Circuit Range/Performance Problem |
| 90 | Evaporative Emission Control System Leak Detected in Fuel Tank Area |
| 91 | Fuel Tank Pressure Sensor Low Input |
| 92 | Evaporative Emission Control System Insufficient Purge Flow |
Transmission Control Unit (TCU) Codes:
| 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 or transmission 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 on Your 90-93 Honda Accord
After addressing the issue indicated by the trouble code, or if you simply want to reset the system, you can easily reset your Honda Accord’s ECU. Here’s the procedure:
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Disconnect the Negative Battery Terminal: Locate the negative terminal on your car battery and use a wrench to disconnect the cable. It’s crucial to disconnect the negative terminal first to prevent accidental shorts.
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Remove the Hazard Fuse: Open the under-hood fuse box and locate the “Hazard” fuse. Pull the fuse out completely.
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Wait: Allow the car to sit for approximately 10-15 minutes. This allows the ECU to fully discharge and reset.
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Reinstall Fuse and Battery Terminal: After waiting, put the “Hazard” fuse back into its slot in the fuse box. Then, reconnect the negative battery terminal securely.
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Start and Idle: Start your Honda Accord without turning on any accessories like the radio, lights, or A/C. Let the engine idle for a few minutes. This allows the ECU to relearn basic engine parameters.
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Turn Off and Restart: Turn the engine off, and then restart it again normally. The ECU should now be reset, and the check engine light should be off, assuming the underlying issue has been resolved.
By following these steps, you can effectively diagnose and address check engine light issues on your 1990-1993 Honda Accord using its OBD1 system. This DIY approach can save you time and money, empowering you to understand your vehicle better. Remember to consult a professional mechanic if you are unsure about any repairs or if the problem persists after resetting the ECU.
