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Service 4WD Light Illuminated, DTC C0374 Set (Inspect Wiring Harness to Transfer Case Speed Sensors, Replace Wiring Harness)

Subject:"Service 4WD" Light Illuminated, DTC C0374 Set (Inspect Wiring Harness to Transfer Case Speed Sensors, Replace Wiring Harness)

Models:2004-2006 Buick Rainier
2003-2006 Cadillac Escalade Models
2003-2006 Chevrolet Avalanche, Silverado, Suburban, Tahoe, TrailBlazer, TrailBlazer EXT
2003-2006 GMC Envoy, Envoy XL, Sierra, Yukon, Yukon XL
2003-2004 Oldsmobile Bravada
2005-2006 Saab 9-7X
with Four Wheel Drive or All-Wheel Drive
and Active All-Wheel Drive (RPO NP4) or Active Two-Speed (RPO NP8) Transfer Case



This bulletin is being revised to add the 2006 model year, Saab 9-7X model and clarify model usage information in the Correction section. Please discard Corporate Bulletin Number 05-04-21-003 (Section 04 -- Driveline/Axle).


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 or AWD system after driving through rain/snow or simply going through a car wash.

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 the wiring harness to the transfer case speed sensors. On Rainier, TrailBlazer, Envoy and 9-7X models, 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 SI. Replace the affected twisted pairs. Do not over-twist the two wires in the replacement harness. Use service connector pack, P/N 88987183, at the speed sensor end and terminal, P/N 15326267, at C101.

Terminal testing tools and service terminals can be found in Terminal Repair Kit J 38125. Terminals are available from SPX/Kent-Moore. Call 1-800-GM-TOOLS (1-800-468-6657).

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.

On the full-size pickup and full-size utility models, replace the 2.2 m (88 in) pigtail harness that runs from the C151 connector under the hood to the transfer case. Use either harness, P/N 15224661 or 15224663, depending on vehicle equipment. Refer to Propshaft Speed Sensors, Front Axle Actuator and Transfer Case Shift Control Switch schematic in SI.

Important: Technicians should verify the integrity of the splice joints after the repair. All splice joints and connections should seal properly against water or a repeat condition can occur.

Parts Information

Part Number

Description

15224661

Harness Asm-Transfer Case Sel

(4WD Full-Size Pickup/Utility w/NP8 and without Four Wheel Steering (NYS)

15224663

Harness Asm-Transfer Case Sel

(4WD Full-Size Pickup/Utility w/NP8 and Four Wheel Steering (NYS)

88987183

Connector-w/leads, 2-way, Female (Speed Sensor)

(All Vehicles)

Warranty Information (excluding Saab U.S. Models)

For vehicles repaired under warranty, use:

Labor Operation

Description

Labor Time

N6630

Wiring And/Or Connector-Transmission/Transfer Case/Transaxle/Front and Rear Axle Control - Repair or Replace

Use published labor operation time

Warranty Information (Saab U.S. Models)

For vehicles repaired under warranty, use:

Labor Operation

Description

Failed Object

Fault/Reason

Location Code

Warranty Type

Repair/Action Code

Labor Time

3714901

Wiring And/Or Connector-Transmission/Transfer Case/Transaxle/Front and Rear Axle Control - Repair or Replace

37149

67

0

01

01

Use Published Labor Operation Time