Manufacturer Code Charts: 74

74-AC REQUEST OUTPUT SIGNAL TOO LOW





For a complete wiring diagram, refer to the Wiring Information. Electrical Diagrams

- When Monitored:
With the ignition on.

- Set Condition:
If the A/C Heater Control detects voltage below 1.51 volts on the (C105) HVAC MUX Control circuit.





NOTE: This DTC must be active for the results of this test to be valid. Do not perform this test if this DTC is stored. Refer to HVAC System Test (MTC) for stored DTC test procedures MTC.

1. CHECK (C105) HVAC MUX CONTROL CIRCUIT VOLTAGE AT A/C HEATER CONTROL C1 HARNESS CONNECTOR




1. Turn the ignition off.
2. Disconnect the A/C Heater Control C1 harness connector.
3. Turn the ignition on.
4. Measure the voltage of the (C105) HVAC MUX Control circuit.

Is the voltage below 4.8 volts?

Yes

- Go To 2

No

- Replace the A/C Heater Control.
- Perform the BODY VERIFICATION TEST. Body Verification Test

2. CHECK (C105) HVAC MUX CONTROL CIRCUIT FOR A SHORT TO GROUND




1. Turn the ignition off.
2. Disconnect the Instrument Cluster C2 harness connector.
3. Measure the resistance of the (C105) HVAC MUX Control circuit between ground and the A/C Heater Control C1 harness connector.

Is the resistance below 10K ohms?

Yes

- Repair the (C105) HVAC MUX Control circuit for a short to ground.
- Perform the BODY VERIFICATION TEST. Body Verification Test

No

- Go To 3

3. CHECK (C105) HVAC MUX CONTROL CIRCUIT FOR AN OPEN




1. Measure the resistance of the (C105) HVAC MUX Control circuit between the A/C Heater Control C1 harness connector and the Instrument Cluster C2 harness connector.

Is the resistance below 5.0 ohms?

Yes

- Replace the Instrument Cluster (CCN).
- Perform the BODY VERIFICATION TEST. Body Verification Test

No

- Repair the (C105) HVAC MUX Control circuit for an open.
- Perform the BODY VERIFICATION TEST. Body Verification Test