Possible Causes
| Possible Causes |
|---|
| ANY UPSTREAM OR DOWNSTREAM O2 SENSOR SIGNAL CIRCUIT SHORTED TO GROUND |
| UPSTREAM O2 SENSOR RETURN CIRCUIT SHORTED TO GROUND |
| DOWNSTREAM O2 SENSOR RETURN CIRCUIT SHORTED TO GROUND |
| ANY UPSTREAM OR DOWNSTREAM O2 SENSOR |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding. Refer to PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE .