U1016 Loss of PCM Serial Communication - HVAC

CIRCUIT DESCRIPTION

DTC U1016 will set if the ignition is ON and the heater and A/C programmer has lost data communication with the PCM.

Diagnosis of this DTC is dependent upon other system symptoms (DTCs) present with U1016.

TEST CONDITION(S)

1. Ignition is ON.

FAILURE CONDITION(S)

1. Open circuit.

ACTION TAKEN

1. Set DTC U1016.

TROUBLE SHOOTING HINTS

1. Using a scan tool attempt to establish communications with PCM.
2. Check CKT 1807 for an open or short to power or ground.
3. Check that PCM is connected to power and ground.
4. If there are multiple Class 2 DTCs current, check for a short to ground or voltage in CKT 1807. Refer to Computer System Diagnosis. Computers and Control Systems
5. Make sure PCM is operating properly. If the PCM is operating normally replace the heater and A/C programmer.
6. DTC P1605 may be present with this DTC. If so, this would indicate that both the PCM and heater and A/C programmer were functional when the DTC was set, but they could not communicate with one another. Refer to the diagnostic chart of PCM DTCs in Computers and Controls for this condition. Testing and Inspection