Reading Codes

Remember that the diagnostic trouble code identification refers only to the circuit, not necessarily to a specific component. For example, fault code 14 may indicate an error in the throttle position sensor circuit; it does not necessarily mean the TPS sensor has failed. Testing of all related wiring, connectors and the sensor itself may be required to locate the problem.

The PCM memory is capable of storing multiple codes. During diagnosis the codes will be transmitted in numerical order from lowest to highest, regardless of the order of occurrence. If multiple codes are stored, always begin diagnostic work with the lowest numbered code.

Make a note of the following:

1. When battery voltage is low, no detection of failure is possible. Be sure to check the battery voltage and other conditions before starting the test.
2. Diagnostic items are erased if the battery or the engine controller connection is detached. Do not disconnect either of these components until the diagnostic material present in the PCM has been read completely.
3. Be sure to attach and detach the scan tool to the data link connector with the ignition key OFF. If the scan tool in connected or disconnected with the ignition key ON, diagnostic trouble codes may be falsely stored and the engine warning light may be illuminated.