P1D56- INTERNAL CONTROL MODULE CPU UNDERVOLTAGE ERROR

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

When Monitored:
With the ignition on.
Set Condition:
The Powertrain Control Module (PCM) detects an internal failure.

Possible Causes
POWERTRAIN CONTROL MODULE (PCM)

1. DTC IS ACTIVE

1.	Ignition on, engine not running.

2.	With the scan tool, erase DTCs in the PCM.

3.	Monitor the scan tool for at least two minutes.

4.	Cycle the ignition key off and on several times, leaving the ignition on for at least 10 seconds at a time.

5.	Start the engine.

6.	Perform several engine run cycles, turning the ignition off for at least 20 seconds between each engine run cycle.

7.	With the scan tool, select View DTCs.

Did this DTC return?

Yes

2. CHECKING THE PCM POWER AND GROUND CIRCUITS

1.	Perform the diagnostic procedure for CHECKING THE PCM POWER AND GROUND CIRCUITS. (Refer to 29 - Non-DTC Diagnostics/Drivability - Diesel - Diagnosis and Testing) .

Were any problems found?

Yes

Repair the PCM power and ground circuit(s) as necessary.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

3. POWERTRAIN CONTROL MODULE

1.	Using the wiring diagram/schematic as a guide, inspect the Powertrain Control Module wiring and connectors.

2.	Look for any chafed, pierced, pinched, or partially broken wires.

3.	Look for broken, bent, pushed out or corroded terminals.

4.	Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Replace the Powertrain Control Module (PCM) in accordance with the service information.
Perform the PCM VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).