Diagnose and fix Service 4 Wheel Drive Message
GM has issued a service bulletin # 09-04-21-001 to address a Service 4 Wheel Drive Message condition on the vehicles listed below. In addition to the Service 4 Wheel Drive Message, you may also have a C0387 or a C0569 trouble code stored.
Vehicles with Service 4 Wheel Drive Message and service bulletin
2009 Cadillac Escalade Hybrid
2007–2009 Chevrolet Avalanche, Silverado, Silverado Hybrid, Suburban, Tahoe, Tahoe Hybrid
2007–2009 GMC Sierra, Sierra Hybrid, Yukon, Yukon Hybrid, Yukon XL
All Equipped with Transfer Case RPO NQF or NQH
Transfer case won’t shift
When the trouble codes are stored and the Service 4 Wheel Drive Message is displayed, the transfer case is inoperative for the rest of that particular key cycle. It will test again and reset the message on the next key cycle if the problem hasn’t been fixed. The codes may be stored with or without you requesting a transfer case shift. The codes and message may also be set during normal driving conditions in Auto 4WD, 4HI or 4LO.
The trouble codes often set intermittently set during extreme cold or warm weather, or when the battery has a low charge.
Cause of Service 4 Wheel Drive message
GM has issued a software update to correct the problem. DO NOT replace the Transmission case control module TCCM. After reprogramming with the most current update, perform a Clutch Reset Procedure (Motor Learn Procedure). Also, if you have C0387, C0387 or C0569 stored, check the transfer case electrical connectors and wiring.
What is trouble code C0387
C0387 Unable to Complete Shift Circuit
The transfer case encoder motor is a bi-directional DC motor. When energized through motor control A or motor control B, the ground connection is provided by the opposing motor control circuit, which is then grounded through the transfer case control module (TCCM) ground circuit. The transfer case motor rotates the actuator shaft which moves the transfer case two/four wheel drive actuator cam and transfer case high/low shift fork to shift the transfer case between the following modes or ranges: 2 HI, 4WD HI, 4WD LOW, Neutral
The transfer case control module monitors the actuator current and sensor output to verify the proper position has been obtained. Deviations in current and position from expected values will cause this DTC to set if the ignition is ON and the system battery voltage is between 10.5–18 V.
Transfer case clutch reset procedure
1. The key must be in the OFF position for at least 30 seconds.
2. Engage parking brake.
3. Place transmission in Neutral.
4. Turn the key to the ACCESSORY position
5. Turn the transfer case shift control switch (TCSCS) to the 2WD HI position for at least 5 seconds.
6. Turn the TCSCS clockwise past the 4WD LO position to the neutral request position and hold for at least 30 seconds.
7. An audible noise from the transfer case encoder motor should occur indicating asuccessful learn procedure.
This procedure applies to other vehicles with the NQH MP3023/4 Transfer Case.
2007-09 Chevrolet Avalanche
2007-09 Chevrolet Silverado
2007-09 Chevrolet Suburban
©, Rick Muscoplat
Posted on by Rick Muscoplat
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