You wake up and Monday and find your car that sat all weekend won't crank. You don't remember leaving any lights on or doors open. What Happened??
Well that's a common problem but the solution is not always easy. This Yukon gave us trouble due to the fact that the problem was intermittent. If it doesn't happen it's hard to diagnose or even test. The battery, starter and alternator tested fine. but some days, overnight, we'd come in and the battery is dead. After hours of testing, pulling fuses and tracing wires we found the problem.
The transfer case module that monitors and controls the 4X4 system would come on intermittent and run down the battery. So disconnect it and let the customer go, right?
Not so easy, the Yukon is 4X4 Automatic. Which means that it has four wheel on demand so without the module the car will possible shift into 4 wheel or 2 wheel intermittently. This is a safety issue and one that warrants repair. Ordered the new Module and repaired the truck.
Computers have a mind of their own and sometimes can have a nervous breakdowns like I almost had with this Truck. Thanks God the customer was reasonable.