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