No Response From A/C Heater Control Module

POSSIBLE CAUSES
- Fused B+ circuit open
- Fused ignition switch output circuit(s) open
- Ground circuit open
- SCI transmit circuit open
- SCI transmit circuit shorted to ground
- SCI transmit circuit shorted to voltage
- A/C heater control module

Diagnostic Test




1.FUSED B+ CIRCUIT OPEN

Turn the ignition off.
Disconnect the A/C Heater Control Module harness connector.

NOTE: Check connector Clean/repair as necessary.

Turn the ignition on.
Measure the voltage of the Fused B+ circuit at the A/C Heater Control Module harness connector.

Q: Is the voltage above 10 volts?

YES: Go to 2
NO: Repair the Fused B+ circuit for an open.Perform BODY VERIFICATION TEST. Body Verification Test




2. FUSED IGNITION SWITCH OUTPUT CIRCUIT(S) OPEN

With the ignition on.
Measure the voltage of the Fused Ignition Switch Output circuits at the A/C Heater Control Module harness connector.

Q: Is the voltage above 10 volts?

YES: Go to 3
NO: Repair the Fused Ignition Switch Output circuit(s) for an open. Perform BODY VERIFICATION TEST. Body Verification Test




3. GROUND CIRCUIT OPEN

Turn the ignition off.
Measure the resistance of the Ground circuit from the A/C Heater Control Module harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go to 4
NO: Repair the Ground circuit for an open. Perform BODY VERIFICATION TEST. Body Verification Test




4. SCI TRANSMIT CIRCUIT OPEN

With the ignition off.
Measure the resistance of the SCI Transmit circuit from the A/C Heater Control Module harness connector to the DLC.

Q: Is the resistance below 5.0 ohms?

YES: Go to 5
NO: Repair the SCI Transmit circuit for an open. Perform BODY VERIFICATION TEST. Body Verification Test




5. SCI TRANSMIT CIRCUIT SHORTED TO GROUND

With the ignition off.
Measure the resistance between ground and the SCI Transmit circuit.

Q: Is the resistance below 100 kohms?

YES: Repair the SCI Transmit circuit for a short to ground. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Go to 6




6. SCI TRANSMIT CIRCUIT SHORTED TO VOLTAGE

Turn the ignition on.
Measure the voltage of the SCI Transmit circuit at the A/C Heater Control Module.

Q: Is the voltage above 0.5 volt?

YES: Repair the SCI Transmit circuit for a short to voltage. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Replace the A/C Heater Control Module.Perform BODY VERIFICATION TEST. Body Verification Test