SPN 627 - FMI 2 (Fault Code 1117)

SPN627 FMI2 (Power Supply Lost With Ignition On - Data Erratic, Intermittent, or Incorrect)
Fault Code 1117
ISB, ISC, and ISL with CM2150 - ECM Power Supply Circuit

Fault Code: 1117
PID(P), SID(S): S251
SPN: 627
FMI: 2/2
Lamp: NONE

REASON: Power Supply Lost With Ignition On - Data Erratic, Intermittent, or Incorrect. Supply voltage to the ECM fell below +6.2-VDC momentarily, or the ECM was not allowed to power down correctly (retain battery voltage for 30 seconds after key OFF).

EFFECT: Possible no noticeable performance effects or engine dying or hard starting. Fault information, trip information, and maintenance monitor data can be inaccurate.

Circuit Description:
The electronic 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 original equipment manufacturer (OEM) power harness through the ECM battery supply stub. This provides a constant power supply for the ECM. The location of the battery will vary with the OEM. Refer to the OEM service manual.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position, and during the power down process (lasting 30 seconds after key OFF).

Conditions for Setting the Fault Codes:
The ECM detects that primary ECM power supply dropped below 6.2-VDC 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:
• The ECM records the fault code immediately when the diagnostic runs and fails.
• 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:
The ECM must see primary ECM battery voltage above +6.2-VDC when the keyswitch is turned off before the fault code will go inactive.

Shop Talk:
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

This fault is set active if the ECM battery supply voltage drops below +6.2-VDC while the keyswitch is in the ON position.

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.

Where the fault code is inactive, familiarize yourself with the vehicle shutdown practices used by the operator. For example, if there are controls inside the cab that can interrupt the (ECM) power supply (before the end of the 30 second power down process after key OFF), these should be considered as a potential cause when the fault code is being addressed. This should be explained to the operator.

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.

An active Fault Code 1117 can prevent critical aftertreatment soot load information from being saved to permanent memory in the ECM. The use of battery disconnect switches to turn the engine off 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. Do not operate the vehicle with an active Fault Code 1117.

Read More:
SPN 1590 - FMI 2 (Fault Code 784)
SPN 703 - FMI 11 (Fault Code 779)


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