No Response From HVAC (A/C Heater Control Module)

NO RESPONSE FROM A/C HEATER CONTROL MODULE

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
- Universal garage door opener/tire pressure monitor
- Instrument cluster
- Power top control module
- A/C heater control module

DIAGNOSTIC TEST

1. CHECK COMMUNICATION WITH OTHER MODULES




Turn the ignition on.
Using the DRB III(R), attempt to communicate with the PCM.

Q: Is the DRB III(R) able to communicate with the PCM?

YES: Go to 2
NO: Perform Symptom *No Response From All Modules. No Response From All Modules

2. CHECK COMMUNICATION WITH OTHER MODULES ON SCI TRANSMIT CIRCUIT




With the ignition on.
Using the DRB III(R), attempt to communicate with either the Instrument Cluster, Universal Garage Door Opener/Tire Pressure Monitor, or Power Top Control Module (if equipped).

Q: Is the DRB III(R) able to communicate with the module selected?

YES: Go to 3
NO: Go to 7

3. 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 4
NO: Repair the Fused B+ circuit for an open. Perform BODY VERIFICATION TEST. Body Verification Test

4. 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 5
NO: Repair the Fused Ignition Switch Output circuit(s) for an open. Perform BODY VERIFICATION TEST. Body Verification Test

5. GROUND CIRCUIT OPEN




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

Q: Is the resistance below 5.0 ohms?

YES: Go to 6
NO: Repair the Ground circuit for an open. Perform BODY VERIFICATION TEST. Body Verification Test

6. 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: Replace the A/C Heater Control Module. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Repair the SCI Transmit circuit for an open. Perform BODY VERIFICATION TEST. Body Verification Test

7. DISCONNECT MODULES





NOTE:
- The Instrument Cluster, Universal Garage Door Opener/Tire Pressure Monitor, A/C Heater Control Module, and Power Top Control Module (if equipped) all use the SCI Transmit circuit at DLC cavity 15 to communicate with the DRB III(R). If one of these modules keeps the SCI Transmit circuit artificially high or low, the DRB III(R) will not be able to communicate with any of the four modules.
- Perform the following steps for each of the modules until communication is restored with the other modules or until each of the modules has been eliminated as the cause of the fault.

Turn the ignition off.
Disconnect each of the modules noted above, one at a time.
Turn the ignition on.
Using the DRB III(R), attempt to communicate with any of the three modules still connected.

Q: Is the DRB III(R) able to communicate with the module selected?

YES: Replace the module that was disconnected when communication was restored to the other two modules. Perform BODY VERIFICATION TEST. Body Verification Test
NO: Go to 8

8. SCI TRANSMIT CIRCUIT SHORTED TO VOLTAGE




Turn the ignition off.
Disconnect the harness connectors for the IC, UGDO/TPM, A/C Heater Control Module, and Power Top Control Module (if equipped).
Turn the ignition on.
Measure the voltage of the SCI Transmit circuit at the A/C Heater Control Module harness connector.

Q: Is the voltage below 0.5 volt?

YES: Go to 9
NO: Repair the SCI Transmit circuit for a short to voltage. Perform BODY VERIFICATION TEST. Body Verification Test

9. SCI TRANSMIT CIRCUIT SHORTED TO GROUND OR OPEN




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

Q: Is the resistance above 100 kohms?

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