For 1990-2009 cars

To read and clear diagnostic trouble codes, use a scan tool.

Use a scan tool to clear diagnostic trouble codes from the PCM memory. Diagnostic trouble codes can also be cleared by turning OFF the ignition and disconnecting the battery power from the PCM for 30 seconds, but this method will also cause all diagnostic information in the PCM memory to be cleared and all the diagnostic tests will have to be ran again.

The Vehicle Identification Number (VIN) is programmed into the PCM. Do not exchange a PCM from another vehicle for testing or replacement. When replacing the PCM, the VIN must also be programmed into the new PCM.

Because the PCM can have a failure which may affect only one circuit, follow the diagnostic procedures in this section to determine which circuit has a problem and where it is.

If a diagnostic chart indicates that the PCM connections or PCM is the cause of a problem and the PCM is replaced, but does not correct the problem, one of the following may be the reason:

• | There is a problem with the PCM terminal connections. The diagnostic chart will say PCM connections or PCM. The terminals may have to be removed from the connector in order to check them properly.

• | EEPROM program is not correct for the application. Incorrect components may cause a malfunction and may or may not set a DTC.

• | The problem is intermittent. This means that the problem is not present at the time the system is being checked. In this case, refer to the Symptoms portion of the manual and make a careful physical inspection of all components and wiring associated with the affected system.

• | There is a shorted solenoid, relay coil, or harness. Solenoids and relays are turned ON and OFF by the PCM using internal electronic switches called drivers. A shorted solenoid, relay coil, or harness will not damage the PCM but will cause the solenoid or relay to be inoperative. The J 34636 tester, or equivalent, provides a fast, accurate means of checking for a shorted coil or a short to battery voltage.