If you own a GM vehicle, then you know two things: the mechanical side is built like a tank. And the electrical side is the work of Satan. We have four GM vehicles, and all four suffer from electrical problems, ranging from annoying to nightmarish. My truck (a 2003 GMC Sierra 2500HD Duramax) is by far the worst. The other ones mostly just whine constantly about low tire pressure and things like that. My truck, on the other hand, takes it to a whole new level. Nearly every sensor, gauge, processor, computer, wiring harness, and black box has been replaced at least once. And still it fails. Yesterday’s failure was the dreaded “Service 4WD” message, which is one of the more famous (and common) failings of GM trucks. The good news is that it’s usually one of two things. Either the sensor on the transfer case is dead (again) or the control panel on the dash has failed (again). Getting the transfer case sensor replaced is about a $1500 job if you take it to the shop. The switch, on the other hand, is well under $100 if you do it yourself. And from what I read on the Internet, the most common failure is cracking solder joints on the circuit board where the wiring harness attaches. I decided I’ve got nothing to lose, so I took a stab at fixing it myself. I took pictures, as I’m sure somebody somewhere will benefit from this (since it’s such a common problem).
Here’s a picture of the buttons in question.
First thing to do is pop the dash facade loose. Drop your steering will all the way down and put the transmission into 1st gear (to get it out of the way). Then the facade will pop off with gentle but firm pulling.
Put it somewhere safe (and if it’s like mine, wash it).
The naked dash.
Here’s the box of evil. There is a tab at the top and on the left side to pop it loose. Takes a little bit of swearing, but it’s not all that hard.
Once it’s loose, remove the two wire harnesses. Be careful to pull the little tabs gently to release the connectors.
There’s the beast. Not the three white tabs on the side. There are three more on the other side. You must very gently pry these up without breaking the plastic while you firmly pull the white part loose on the back. Having an extra pair of hands for this makes it much easier.
Here’s the inside. The clear plastic part comes right off.
Now heat up a soldering iron and melt the solder on each of the twelve pins, letting it re-flow around the pin. Don’t hold it too long, or you’ll melt the plastic.
So far, so good. When I put everything back together, it starting working again. Obviously, that’s not the same as saying it’s definitively fixed, but then again, it’s a GM, so it’s never definitively fixed. It’s just waiting for it’s next failure. I hope it’s this and not another transfer case sensor. I’m getting tired of dumping thousands of dollars into electrical repairs on this thing. Remember when a transfer case had a lever that protruded up through the floor? Those didn’t have electrical problems. I’m not sure I understand why we ever got away from that.