"I Was Driving and I Lost My Signals and Power Windows"
Driving back home from Las Vegas I called a shop I occasionally do work for that is on my route home. I wanted to see if I could grab some work. They had a Nissan that they just changed the BCM on that needed immobilizer programming. I stopped by the shop and completed the key learn. The truck started and ran. Then I got the rest of the story. The technician came up to the vehicle and tried to use the electric windows. They did not work. He then tried the turn signals which also did not work. He stated that the customer was driving and lost many accessories all at one time. His diagnosis led him to believe the BCM was at fault. My new quest was to find the fault before the customer brought the spare key for the truck.
In order to track the problem the first task was to check powers, grounds and comm lines. There were CAN communication codes but I opted to go the power route. Looking at the wiring diagram there were three power feeds to the BCM. The BCM then fed the windows. Two of the leads had power. The third White/ Black wire had no power at the BCM. It showed that it was protected by a 50 AMP fuse and some diagrams showed a fusible link. The tech who diagnosed it was now engaged with me in finding the issue. I was stumped as the 50A fuse had no power on either side of the fuse. I thought maybe a bad / hot connection below the fuse block. The tech found the feed wire to be on the positive battery terminal. There was lots of corrosion at the connection but it was not the problem. diag.net/file/fgfmdh1sf…
Right below the connector the wire was expanded. Definitely a problem but not "the" problem. The tech pulled back the covering from the large White wire. Another expanded portion. The fusible link was actually there. Behold the problem! How this happened in the dry climate of St George, Utah there is no clue. Maybe the vehicle came from somewhere else. diag.net/file/f2xvb71mt…
We were able to show a positive result while the customer was present. Permanent repair will happen today and all will be good.
How can you condemn a module without load testing the power and ground circuits? Such a simple procedure but I see shops failing to perform it all the time.
"How can you condemn a module without load testing the power and ground circuits?" hopefully with the SHOP's money....not the customer's. :-)
Because "it has 12 volts" and I've been guilty of that myself, as have we all. Just because it's got 12v doesn't mean that voltage can do anything.
Great pics!!! Never seen one with a link like that. Thanks Mike
He didn't condemn the module, the shop's tech did. Not all techs are created equal. The cause appears to be corrosion from battery acid migration through the wire, via capillary action.