Bus (+/-) Signals Open/No Response From HVAC

Tests 1 - 3:

Tests 4 - 7:

Tests 8 - 9:

SYMPTOM
BUS ± SIGNALS OPEN OR NO RESPONSE FROM HVAC

POSSIBLE CAUSES
- Attempt to communicate with the CTM
- Replace fuse # 25
- A/C heater control shorted to ground
- Fused ignition switch output circuit shorted to ground
- Junction block shorted to ground
- Ground circuit(s) open
- Fused ignition switch output circuit open
- Open PCI bus circuit
- A/C heater control