Possible Causes
| Possible Causes |
|---|
| O2 SENSOR 1/1 SIGNAL CIRCUIT OPEN OR SHORTED |
| O2 SENSOR 1/1 RETURN CIRCUIT OPEN OR SHORTED |
| O2 SENSOR 1/1 HEATER CIRCUITS OPEN OR SHORTED |
| RESTRICTED INTAKE AIR FLOW (PLUGGED AIR FILTER) |
| LEAK IN THE EXHAUST SYSTEM |
| UPSTREAM AND DOWNSTREAM O2 SENSOR HARNESS CONNECTORS SWITCHED |
| O2 SENSOR 1/1 INSTALLED INCORRECTLY |
| O2 SENSOR 1/1 |
| ENGINE MECHANICAL ISSUE CAUSING O2 SENSOR CONTAMINATION |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding. Refer to PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE .