P125A

P125A-POWER ENABLE CONTROL CIRCUIT LOW





For a complete wiring diagram refer to the Wiring Information Electrical Diagrams. Electrical Diagrams

Theory of Operation

The Smart Power Relay supplies 12-volts to the Mass Airflow Sensor, the EGR Airflow Control Valve and the Variable Geometry Turbocharger. The Smart Power Relay Driver circuit is a low side driver controlled by the ECM. The Smart Power Relay is powered up at key on, and remains powered until just after key off. The power supply to the Smart Power Relay is wired directly from the TIPM. The ECM will light the MIL lamp and disable regeneration mode immediately after this diagnostic runs and fails. During this time there will likely also be voltage supply faults for the Mass Airflow Sensor, the EGR Airflow Control Valve and the Variable Geometry Turbocharger. The ECM will turn off the MIL lamp once the diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:
Key on, Smart Power Relay commanded on.

- Set Condition:
The Smart Power Relay is commanded on by the ECM, and feedback voltage is reading high.





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

1. ACTIVE DTC
1. Ignition on, engine not running.
2. With the scan tool, read DTC's.

Is P125A active?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. ECM
1. Replace the Smart Power Relay.
2. Turn the ignition on.
3. With the scan tool, erase DTCs.
4. Turn the ignition off for 30 seconds.
5. Turn the ignition on.
6. With the scan tool, read DTCs.

Did the DTC reset?

Yes

- Replace ECM.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Repair complete.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test