The Under the Hood
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Dear Motor Medics, I have a 2004 GMC Yukon and I’m having a 4x4 problem. The system will work one time then not the next. When I take it to the shop it seems to be the time that it is working correctly.
The problem it has is when I switch to 4x4 high the light just blinks then is stays in the 2wd position. Sometimes when I switch to low 4x4 then back to high it will work just fine until I put it back in the 2wd position.
Jack in Charleston, West Virginia
Dear Jack, Problems with systems that seem to always work when you have it in the shop are as big a pain for the mechanics as it is for you as the driver. The systems have computers that can often give codes which can help with the diagnostics, but they don’t always indicate the exact cause and without the system failed at the moment it’s being inspected makes it hard to diagnose and confirm repairs.
The most often found issue we see when a 4x4 system in a GM truck of your model year fails like this is a failed shift motor or shift module. Both parts can be expensive so if you can get it to happen while at a shop so they can give a 100% accurate diagnosis it will go a long way to helping you save money and get it repaired right on the first visit. Take care, The Motor Medics
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