Obtaining and clearing Diagnostic Trouble Codes (DTCs)

1. All models covered by this manual areequipped with on-board diagnostics. When the PCM recognizes a malfunction in a monitored emission or engine control system, component or circuit, it turns on the Malfunction Indicator Light (MIL) on the dash. The PCM will continue to display the MIL until the problem is fixed and the Diagnostic Trouble Code (DTC) is cleared from the PCM’s memory. You’ll need a scan tool to access any DTCs stored in the PCM.

2. Before outputting any DTCs stored in thePCM, thoroughly inspect ALL electrical connectors and hoses. Make sure that all electrical connections are tight, clean and free of corrosion. And make sure that all hoses arecorrectly connected, fit tightly and are in good condition (no cracks or tears).

Accessing the DTCs

3. The Diagnostic Trouble Codes (DTCs)can only be accessed with a code reader or scan tool. Professional scan tools are expensive, but relatively inexpensive generic code readers or scan tools (see illustrations 2.4a and 2.4b) are available at most auto parts stores. Simply plug the connector of the scan tool into the diagnostic connector (see illustration). Then follow the instructions included with the scan tool to extract the DTCs.

i.3 The Data Link Connector (DLC) is located under the dash, to the left of the steering column (Civic shown)

4. Once you have outputted all of the storedDTCs, look them up on the accompanying DTC chart.

5. After troubleshooting the source of eachDTC, make any necessary repairs or replace the defective component (s).

Clearing the DTCs

6. Clear the DTCs with the code reader orscan tool in accordance with the instructions provided by the tool’s manufacturer.

Diagnostic Trouble Codes

7. The accompanying tables are a list of theDiagnostic Trouble Codes (DTCs) that can be accessed by a do-it-yourselfer working at home (there are many, many more DTCs available to professional mechanics with proprietary scan tools and software, but those codes cannot be accessed by a generic scan tool). If, after you have checked and repaired the connectors, wire harness and vacuum hoses (if applicable) for an emission-related system, component or circuit, the problem persists, have the vehicle checked by a dealer service department or other qualified repair shop.

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