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HVAC Control Unit
DTC Troubleshooting: U128D
DTC U128D:
Lost Communication with Gauge Control Module (HVAC Control Unit )
1. Clear the DTCs with the HDS.
2. Turn the ignition switch to LOCK (0) and then back to ON (II).
3. Do the self-diagnostic function with the HDS.
4. Check for DTCs.
Is DTC U128D indicated?
YES -
Go to step 5.
NO -
The system is OK at this time. Check for loose wires or poor connections on the gauge control module and HVAC control unit circuit.
5. Select B-CAN Control Units Information in the BODY ELECTRICAL menu.
6. Select Check Connected Control Units in the B-CAN Control Units Information menu.
Is the gauge control module detected?
YES -
Substitute a known-good HVAC control unit, and recheck. If the symptom/indication goes away, replace the original HVAC control unit HVAC Control Unit Removal/Installation.
NO -
Go to step 7.
7. Disconnect the gauge control module 32P connector.
8. Disconnect HVAC control unit connector A (24P).
9. Check for continuity between the following terminals of the gauge control module 32P connector and HVAC control unit connector A (24P).
Is there continuity?
YES -
Go to gauge control module input test Component Tests and General Diagnostics.
NO -
Repair an open in the wire between the HVAC control unit and the gauge control module.