Mechanics

2WD/4WD JUMPS TO NEUTRAL

1997 GMC Acadia • V8 4WD •

1997 GMC K1500 Truck. I will be driving along in 2wd and it will pop out of 2wd to neutral. I have to pull over and stop to put it in 2wd and continue. What is the problem with the transfer case.
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Billbarth
December 16, 2010.



Perform the following to check if any trouble codes are stored in TCCM.

RETRIEVING DTCS
NOTE: Diagnostic Trouble Codes (DTCs) are displayed on 3 transfer case shift select buttons. When proper conditions are met, select buttons will blink to indicate DTC from "1" to "4".

1. Turn ignition off for at least 6 seconds. Locate DLC near right side of steering column. Install jumper wire between diagnostic pigtail (Orange wire at DLC terminal No. 13) and ground.

2. Turn ignition to run position (engine off). Observe shift select buttons. If all shift select buttons blink once at same time then stop, no DTCs are stored. If only one code is stored in TCCM memory, that code will blink repeatedly, with a 3 second delay between sequences. If more than one code is present, next code will flash after a 3 second delay, then sequence will repeat. Count number of blinks for each code. See Fig. 1.

3. Write down all DTCs. After retrieving DTCs. Clear TCCM memory and repeat procedure. See CLEARING DIAGNOSTIC TROUBLE CODES. If DTCs return, perform appropriate test. See DTC DEFINITIONS under SELF-DIAGNOSTIC SYSTEM.


KHLow2008
Dec 16, 2010.