PCM Communication Failure

PCM COMMUNICATION FAILURE

WHEN MONITORED
With the ignition on.

SET CONDITION
The Powertrain Control Module (PCM) (for gasoline engines) or Engine Control Module (ECM) (for diesel engines) broadcasts a message on the PCI Bus that provides engine RPM and vehicle speed. This DTC will set if the A/C Heater Control does not receive this message for more than 5 seconds.

POSSIBLE CAUSES
- Faults present in the powertrain system
- PCM not broadcasting message
- ECM not broadcasting message
- A/C heater control not receiving message

Diagnostic Test

1. VERIFY THAT THE PCM COMMUNICATION FAILURE DTC IS ACTIVE
Turn the ignition on.
With the DRBIII(R), erase HVAC DTCs.
Cycle the ignition switch and wait approximately 30 seconds.
With the DRBIII(R), read active HVAC DTCs.

Q: Does the DRBIII(R) display: PCM Communication Failure?

YES: Go To 2
NO: A technician may not have erased this DTC following a module or PCI Bus repair. If possible, verify if the vehicle was recently in for this type of service. Otherwise, visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals. Repair as necessary. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

2. CHECK FOR DTCS IN THE PCM OR ECM
With the DRBIII(R), read PCM or ECM DTCs.

Q: Does the DRBIII(R) display any DTCs?

YES: (Gasoline Engines)
Diagnose and repair the DTC(s). Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
YES: (Diesel Engines)
Diagnose and repair the DTC(s). Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3

3. VERIFY THAT THE PCM OR ECM IS BROADCASTING THE MESSAGE ON THE PCI BUS
With the DRBIII(R) in HVAC, select Monitor Display and then select PCI Bus Messages.
From the list, select the following:
- Engine RPM
- Vehicle Speed

Q: Does the DRBIII(R) display NO RESPONSE after either of these messages?

YES: (Gasoline Engines)
Perform the *No Response From PCM (PCI Bus) diagnostic procedure. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
YES: (Diesel Engines)
Perform the *No Response From ECM (PCI Bus) diagnostic procedure. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace the A/C Heater Control. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test