Diagnostic Aids

Be sure to inspect the ECM and the engine grounds for being secure and clean.

A short to voltage in one of the sensor circuits can cause DTCs 14, 21, 23, or 33 to be set.

If a sensor input circuit has been shorted to voltage, ensure that the sensor is not damaged. A damaged sensor will continue to indicate a high or low voltage after the affected circuit has been repaired. If the sensor has been damaged, replace it.

An open in the sensor ground circuit between the ECM and the splice will cause DTCs 14, 21, 23 or 33 to set.

A short to ground in the 5-volt reference circuit or an open in the 5-volt reference circuit between the ECM and the splice will cause DTCs 15, 22, 25, or 34 to set.

Inspect for the following conditions:

• Inspect for a poor connection at the ECM. Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal-to-wire connection.
• Inspect the wiring harness for damage. If the harness appears to be OK, observe an affected sensor's displayed value on the scan tool with the ignition ON and the engine OFF while moving the connectors and wiring harnesses related to the affected sensors. A change in the affected sensor's displayed value will indicate the location of the fault.