TB10 - Diagnostic Trouble Codes 633 and 691

Diagnostic Trouble Code (DTC) 633 indicates "4x4L" switch position detected during Key On Engine Off (KOEO) Quick Test. DTC 691 indicates 4x4L switch failure either open or shorted.

- Possible causes:

- Damaged 4x4L switch.

- 4x4L harness open or shorted.

- Damaged generic electronic module.

- Damaged Powertrain Control Module (PCM).

- Are 4x2 or 4x4H selected during Quick Test?

Yes -- Go to TB11. TB11 - Check 4X4 Signal From Generic Electronic Module

No -- Select "4x2" or "4x4H" and rerun Quick Test. Quick Test Appendix (Detailed Testing Instructions)