P056D

P056D-REDUCTANT CONTROL MODULE SYSTEM VOLTAGE

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

- When Monitored:
Continuously with the ignition on.

- Set Condition:
The battery voltage detected by the DEF Dosing Control Unit is below or above a calibrated threshold.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC

NOTE: If DTCs P0562 or P2503 are present, repair those DTCs before continuing with this test.

NOTE: If the vehicle was jump started, and there was a momentary voltage spike of 16 Volts, this DTC could be set.

1. Turn the ignition on for one minute, engine not running.
2. With the scan tool check for active DTCs.

Is the DTC active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION - 6.7L diagnostic procedure. Intermittent Condition Test

2. CHECK THE BATTERY TERMINALS AND LOAD TEST THE BATTERIES
1. Perform battery load test using the Midtronics Micro 420 battery system tester.
2. Inspect the terminals of both batteries for signs of corrosion.

Did both batteries pass the Midtronics test and have no signs of corrosion?

Yes

- Go To 3

No

- Replace the defective battery or clean the battery posts and terminals and retest.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

3. CHECK THE CHARGING SYSTEM OUTPUT
1. Reconnect the battery terminals.
2. Perform a check of the charging system. Testing and Inspection.

Is the charging system performing properly?

Yes

- Go To 4

No

- Diagnose and repair the charging system.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK THE DEF DOSING CONTROL UNIT 12-VOLT SUPPLY CIRCUITS
1. Turn the engine off, ignition on.
2. Disconnect the DEF Dosing Control Unit C2 harness connector.
3. Using the wiring diagram as a guide, measure the voltage of the 12-Volt Supply circuits at the DEF Dosing Control Unit C2 harness connector.

Do the DEF Dosing Control Unit 12-Volt Supply circuits read battery voltage +/- 0.2 of a Volt?

Yes

- Go To 5

No

- Using the wiring diagram as a guide, repair the 12-Volt Supply circuits for an open or high resistance. If the fuse in the circuit is found to be open, check the circuits for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

5. CHECK THE DEF DOSING CONTROL UNIT GROUND CIRCUITS
1. Turn the engine off.
2. Using the wiring diagram as a guide, measure the resistance between ground and the ground circuits at the DEF Dosing Control Unit C2 harness connector.

Do the DEF Dosing Control Unit ground circuits measure below 5.0 Ohms?

Yes

- Check the DEF Dosing Control Unit C2 connector for signs of cracks, water intrusion, debris, or corrosion that could affect the connection.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Using the wiring diagram as a guide, repair the ground circuits for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.