99 gmc 4wd switch seems to only work when it chooses too.
I rarely use my 4wd switch but it seems as if when i need it the most it won't work. push the button,nothing happens. Eventually it will light up and properly engage. However when it becomes time to return to 2high it seems to be the same result. Sometimes it works fine and other times only when it chooses.
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Re: 99 gmc 4wd switch seems to only work when it chooses...
The switch operates a selenoid which in turn switches your vehicle into or out of 4x4. your selenoid might be sticking instead of the switch being the problem.. nothing beats the old stick which you grab and put it where you want it ...
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If it has the push button controls on the dash I have had those fail frequently. A lot of times you may push the button and the light may blink and then still stay in 2wd. That switch is also the control module for the 4wd. If it is the know select you need to check for power at the actuator on the transfer case.
no not normal. check center of firewall the is a switch with 3 vacuum line CHECK THEM ALL this is your 4wd selector. if thats okay you might need the switch on the front trasfer case about $20 just unscrews easy fix.
Subject: "Service 4WD" Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch) Models: 1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL) with Four Wheel Drive and NVG 236/246 Transfer Case (RPO NP8)
Condition: Some customers may comment on the Service 4WD indicator illuminating. Upon investigation, the technician may find DTC B2725 set.
Cause: The condition may be due to a intermittent fault in the transfer case shift control switch.
Correction: Important: The transfer case shift control module should not need replacement. DO NOT replace P/N 15749703 unless diagnosis points to the module as the malfunction.
Replace the transfer case shift control switch using published Service Information procedures.
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Ive gone thru this THREE TIMES w/ my '99! Theres a thin, rubber vacuum hose that wears thin, gets dirt/oil/water in it & shorts a relay. The last mechanic replaced the hose w/ steel brakeline & Ive had no problems for 2 yrs.
I have had the same problem with my 2000 jimmy. Disconnect the battery for approx 1 minute and then reconnect, this should reset the computer. It has worked for me every time. I was told it was a glitch with GMC.