4WD System - 4WD Lamp ON/DTC C0374/Erratic 4WD Operation
TSB SB06-05-S001Service 4WD Light Illuminated, DTC C0374 Set
(This Bulletin Supersedes SB05-05-5005)
ISSUE DATE: APRIL 2006
Affected Vehicles
2003-2006 Isuzu Ascender (US/UT) with 4WD
Service Information
This bulletin is being revised to add the 2006 model year, and to update the Service Procedure.
Condition:
Some customers may comment on intermittent illumination of the "Service 4WD" light. Upon investigation, the technician may find DTC C0374 set. The customer may also comment on intermittent erratic operation of the 4WD system after driving through rain/snow or simply going through a car wash.
Possible Cause:
The speed sensor signal may have become corrupted. Possible openings in the speed sensor wire insulation (twisted pairs) can allow water intrusion. Also, wire connections contaminated by water may result in short circuits and erroneous speed sensor readings. This most often occurs on the rear speed sensor circuit.
Correction:
Inspect Wiring Harness to Transfer Case Speed Sensors, Replace Wiring Harness if needed.
Service Procedure
Inspect the wiring harness to the transfer case speed sensors. Fabricate a replacement speed sensor harness between the C101 connector and the speed sensors. Refer to Speed Signal, Front Axle Actuator, and Indicators schematic in the Service Manual. Replace the affected twisted pairs. Do not over-twist the two wires in the replacement harness. Use service connector pack, P/N 8-88987-183-0, at the speed sensor end and terminal, P/N 8-15326-267-0, at C101.
Terminal testing tools and service terminals can be found in the Kent-Moore Terminal Repair Kit J 38125-A. Contact Kent Moore at 1-800-345-2233.
The smaller transfer case harness splices into the larger chassis harness a few inches in front of the crossmember. The chassis harness routes along the left side of the frame under the driver door area.
Use nylon tie straps to secure the fabricated harness to the main chassis harness between the transfer case and C101.
IMPORTANT:
Technicians should verify the integrity of the splice joints after the repair. All splice joints and connections should seal properly against water or condition can occur again.
Parts Information
Warranty Claim Information
Use the labor operation shown.
NOTE:
1. Labor Time includes administrative time allowance.
2. Information released on paper and electronic format prior to bulletin release cannot be updated. For the most current and up to date information refer to the website.
3. Always refer to the Isuzu Service Policy Procedure Manual for specific details on warranty coverage and policies.
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