TB8 - Check Continuity of Control Switch Harness

- Key "OFF".

- Breakout Box connected, Powertrain Control Module (PCM) disconnected.

- Appropriate switch disconnected.

- For 4x4 Low circuit:

- Measure the resistance between test pin 12 at the breakout box and 4x4 Low circuit at 4x4 Low switch touch drive module vehicle harness connector.

- For Transmission Control Switch (TCS) / Transmission Control Indicator Lamp (TCIL) circuit:

- Measure the resistance between keypower at the fuse panel (fuses) (ohmmeter positive probe) and power side of transmission control switch vehicle harness connector (ohmmeter negative probe).

- Measure the resistance between test pin 41 at the breakout box and signal side of transmission control switch vehicle harness connector.

- Are both resistances less than 5.0 ohms?

Yes -- Go to TB9. TB9 - Check Harness Circuit(s) For Shorts to Power

No -- Service open circuit(s). Remove breakout box. Reconnect all components. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)