SPN 168 - FMI 16 (Fault Code 442)

SPN 168 - FMI 16 (Fault Code: 442)
SPN168 FMI16
ISB, ISC, and ISL with CM2150 - Unswitched Battery Supply Circuit

Fault Code: 442
PID(P), SID(S): P168

SPN: 168
FMI: 0/16

REASON: Battery 1 Voltage - Data Valid but Above Normal Operational Range - Moderately Severe Level. ECM supply voltage is above the maximum system voltage level.

EFFECT: Possible electrical damage to all electrical components.

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. There is one 30-ampere fuse in the unswitched battery wire to protect the OEM harness. The ECM receives switched battery input through the vehicle keyswitch wire when the vehicle keyswitch is turned on. The battery return wires are connected directly to the negative (-) battery post.

Component Location:
The ECM is located on the intake side of the engine. 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).

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 ECM detects that the main battery supply voltage is greater than 36-VDC.

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, recalibrate the ECM.

This fault code is logged when the ECM battery supply voltage exceed 36-VDC. Causes of this fault code include:
• Faulty alternator or regulator that is overcharging the system
• Batteries connected in series instead of parallel
• Incorrect jump-starting procedure.

Read More:
SPN 168 - FMI 18 (Fault Code 441)
SPN 558 - FMI 13 (Fault Code 432)


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