B1172

B1172-REAR CONTROL POWER SUPPLY CIRCUIT LOW





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

Theory of Operation

The Rear A/C Heater Control works in conjunction with the A/C Heater Control to control the rear blower motor, rear temperature control and rear mode control. The Rear A/C Heater Control is constantly monitored by the A/C Heater Control for proper operation. If the monitored signal and power circuits are out of a calibrated range a DTC will set.

- When Monitored:
With the ignition on.

- Set Condition:
If the A/C Heater Control detects a voltage less than 4.3 volts for 5.0 seconds on the 5 Volt Supply circuit. If a valid voltage is detected for 1 second the DTC will change from active to stored and stay in the controllers memory for 100 consecutive ignition cycles.





Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

1. VERIFY THE DTC IS ACTIVE
1. Ignition on, engine not running.
2. With the scan tool, erase HVAC DTCs.
3. Turn the ignition off, wait 10 seconds, and turn the ignition on. NOTE: Make sure the Rear Control Lockout on the A/C Heater Control is not turned on.

4. With the scan tool, read HVAC DTCs.

Does the scan tool display this DTC as active?

Yes

- Go To 2

No

- Go To 3

2. CHECK THE (C800) 5 VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND




1. Turn the ignition off to the lock position.
2. Disconnect the A/C Heater Control C3 harness connector.
3. Disconnect the Rear A/C Heater Control harness connector.
4. Measure the resistance between ground and the (C800) 5 Volt Supply circuit.

Is the resistance below 100k Ohms?

Yes

- Repair the (C800) 5 Volt Supply circuit for a short to ground.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Replace the A/C Heater Control (front).
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

3. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. With the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
4. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, or partially broken wires.
5. Check the connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals.
6. Wiggle the wiring and connectors while checking for shorted and open circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.