Two problems have recently started with the 4WD. While driving down the road the indicator lights on the dash will switch over to the 4 HI light from the
2 HI. Pushing the switch on the dash always takes it back to 2 HI. I really do not think the transfer case switches as there is absolutely no change in the way the vehicle operates. The various speeds that it happens has been as high as 70 + mph or as low as 15 mph (always has happened on paved roads). This has occurred several times in the past month.The second occurs while troubleshooting. When I push the switch to go to 4 HI it blinks for 15 seconds then switches back to 2 HI. I can not get it to engage by using various combinations of shift techniques that are described in the owners manual. If I engage the 4LO it always shifts into gear and this is confirmed by driving it. When it does shift into 4 LO the 4HI light also stays lit steady.
The vehicle is a 97 Jimmy with 205K on it. Went through the 4 WD system last year. Replaced the front axle indicator switch, vacuum lines, transfer case switch (3 prong vacuum), and the 4wd dash switch (electrical). Just checked the 4wd actuator motor (vacuum) that engages he front axle. It works properly and holds a vacuum (tested with a manual vacuum pump). The only major items not replaced are the TCCM and the Decoder motor on the transfer case it self.
I have googled and looked for troubleshooting advice from others with this similar vehicle and have come to the conclusion that one of the last two items above is intermittent. The durn items are way expensive and I usually would not trust electrical items like these from junk yards.
- Is there a way to reset the TCCM for troubleshooting? I have read a couple of threads that suggested this but could not determine how except pulling the power. One talked about pulling fuses and cycling the ign.
- What is your thoughts on which of the above is intermittent?
- What else have I missed?
As Always, TIA GM