PACCAR PX-9 CM2350 (2013-17) Fault Code:1117 PID:SID251 SPN:3597 FMI:2 Power Supply Lost With Ignition On - Data Erratic, Intermittent, or Incorrect - ECM TRUCKS (2025)

Reason:
Power Supply Lost With Ignition On – Data Erratic, Intermittent, or Incorrect. Supply voltage to the ECM fell below a calibrated limit momentarily, or the ECM was not allowed to power down correctly (retain battery voltage for 30 seconds after key OFF).

Effect:
Possible reduced engine performance

Circuit Description:
The engine control module (ECM) receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. The ECM receives switched battery input through the vehicle keyswitch wire when the vehicle keyswitch is turned ON.

Component Location:
The ECM is connected to the battery by the OEM harness. This direct link provides a constant power supply for the ECM. The location of the battery will vary with the original equipment manufacturer (OEM). Refer to the OEM service manual.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the primary ECM power supply dropped below a calibratible value while the keyswitch was in the ON position. The fault code will be active when the keyswitch is turned ON following the incomplete power-down event.

Action Taken When the Fault Code is Active:
1) The ECM logs the fault code immediately when the diagnostic runs and fails.
2) Power-down data like trip information, maintenance monitor, and fault information will not get saved to permanent memory when the keyswitch is turned OFF.

Conditions for Clearing the Fault Code:
1) To validate the repair, start the engine, let it idle for 1 minute, and then shutdown the engine.
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
Make sure the ECM unswitched battery supply is coming directly from the battery and not the starter. If unswitched power is coming from the starter, it is possible for the battery voltage to drop low enough during cranking to set this fault active.This fault can also be caused by resistance in the ECM battery supply (+) or (-) circuits. Resistance in these circuits can cause the voltage level at the ECM input to drop low enough to set Fault Code 1117 active. Use of battery disconnect switches to turn off the engine or any device that disconnects battery voltage to the ECM within 10 seconds of turning the keyswitch OFF can cause damage to the aftertreatment system. The vehicle should not be operated with an active Fault Code 1117. Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

Possible Causes:
1) Inactive fault codes
2) Faulty batteries
3) Bad power connector
4) Blown fuse

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