Possible Causes
| Possible Causes |
|---|
| (K299) O2 1/2 HEATER CONTROL CIRCUIT OPEN |
| (Z904) O2 1/2 HEATER GROUND CIRCUIT OPEN |
| O2 SENSOR HEATER ELEMENT |
| PCM |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. See DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure .