Possible Causes
| Possible Causes |
|---|
| (K99) O2 1/1 HEATER CONTROL CIRCUIT OPEN |
| (Z903) O2 1/1 HEATER GROUND CIRCUIT OPEN |
| 1/1 O2 SENSOR |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Refer to PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE .