Ascender 4WD V8-5.3L (2004)
Speed Sensor: Customer Interest
Drivetrain - 'Service 4WD' Lamp ON/DTC C0374
TSB SB07-05-S001
Issue Date: SEPTEMBER 2007
Affected Vehicles
2003-2007 Isuzu Ascender with 4WD
Service Information
This bulletin is being revised to add the 2007 model year and to update information in 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. Completely inspect and test all wiring. 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. Wires should be twisted at a rate of 9 revolutions per foot.
Use service connector pack, P/N 8-88987-993-0, 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.
Warranty Claim Information
Always refer to the Isuzu Service Policy Procedure Manual for specific details on warranty coverage and policies. Reference published Labor Time
Guide for claim processing, if applicable.
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