How to Read and Reset Honda Check Engine Light Codes

If your car develops a fault on board diagnostics light up the check engine light. This guide shows you how to find out what the problem is.

This facility is built into the Primary Control Module (PCM) and is designed to alert the driver to a system component fault. Some faults may result in higher than normal emissions of harmful exhaust/fuel vapour gases or signal a more serious problem. Either way, the car's engine needs attention. Reading the check engine light codes will speed up the engine management troubleshooting procedure.

Should an engine management component fail, the incorrect (or implausible) signal is recognised by the PCM, which stores a Diagnostic Trouble Code (DTC) and, where appropriate, illuminates the Malfunction Indicator Light (MIL)/Check Engine Light (CEL) in the instrument cluster.

To retrieve any stored DTCs, a fault code reader must be connected to the vehicle's data link connector (located above the Service Check Connector) or read from the MIL in the instrument cluster.

Reading the Check Engine Light on Honda Civic's Accord

These instructions work for the Honda Civic, Accord, and Preludes between 1992 and 2000.

The service check connector (2-pin) is under the dashboard, above the passenger side kick panel. By default, it is inserted into a green rubber housing. It is grey for 92-95 models; for 96-00 models, it's blue. The codes can be read by bridging the two pins in the service connector and reading the MIL on the instrument cluster (all models). Vehicles 2000 onwards are fitted with a 16-pin diagnostic behind the centre console on the passenger side. A fault code reader is required to retrieve or clear codes via this connector.

Even if you don't have a code reader, you can still view any DTCs stored in the PCM memory. Simply fit a bridging wire into the service check connector and turn the ignition switch to the ON position. The codes, if present, will blink a sequence in the MIL to indicate a system or component failure. This backup method ensures that you can still diagnose your car's issues, even without a code reader.

The MIL will blink longer to represent the first digit and then blink short for the second (for example, one long and six short would be code 16). If the system has more than one problem, the codes will be displayed in sequence, there will be a pause, and then the codes will repeat.

When the PCM sets DTC, the MIL will come on, and the trouble code will be stored in the memory. The trouble code will stay in the PCM until the voltage to the PCM is interrupted. Remove the BACK-UP fuse from the fuse relay box located in the engine compartment for at least ten seconds to clear the memory. NOTE - This will also clear any radio presets/codes.

Resetting the Check Engine Light and Clear Codes

Resetting the Check Engine Light and clearing the codes stored in the PCM might sound daunting, but it's a safe and straightforward process. Once you have diagnosed and fixed the problem, you can reset the Check Engine Light to prevent it from staying lit. This can be done by pulling the ECU memory fuse from the fuse box in the engine bay, waiting a few minutes and putting it back in. On my Civic, it is the FI ECU 7.5A fuse, but check your owner's book or workshop manual for the specific fuse in your model. You can also disconnect the battery for a few minutes. Rest assured, these steps are safe and will not cause any harm to your car.

Honda Civic Diagnostic Trouble Codes Table