Transfer Case - MIL ON/DTC C0374/Erratic 4WD Operation

SOURCE: Isuzu Service News

TITLE: 4WD Intermittent, MIL DTC C0374, or Erratic 4WD Operation

APPLIES TO: 03-05 Ascender 4WD

SERVICE TIP:

Condition:

Some customers may comment Service 4WD Light comes on intermittently with DTC C0374. Concern could also be described as intermittent erratic operation of 4WD.

Correction:

Check speed sensor wiring harness from the bulkhead connector to the transfer case speed sensors. This harness may have been twisted too tight during production. This can cause the wire insulation to stretch and allow openings to develop in the insulation. Openings in the wire insulation together with water intrusion may result in short circuits and erroneous speed sensor readings.

Replace affected twisted pairs in the harness from the bulkhead connector to the speed sensor. Fabricate a replacement harness as required. Be careful not to over twist the two wires in the replacement harness.

Check the chassis harness as it routes along the left side of the frame, under the driver's door area. The smaller transfer case harness splices into the larger chassis harness, a few inches in front of the cross member. This is the lowest point (or dip) where the chassis harness can trap water.

Water trapped in the harness acts as a conductor causing erratic prop shaft speed sensor readings which result in DTC C0374. Create a permanent opening in the conduit to allow the water to drain.