Manager Forum

2003 Cadillac DHS with over 200K on the clock

Customer complained of power windows and locks not working, temp and fuel not working. stability and theft lights coming on. Had codes U1040, U1064, U1065, U1066, U1096, and U1192. These are all related to a loss of communication between various modules. I have a feeling that the problem is most likely in ignition 1 relay or the ignition switch.

Has anyone had simular problems with one of these and could shed some light on the problem?
One more thing that I was able to squeaze out of the customer is that the engine does not cut out at all when this happens. Some times the guages will fluctuate and at times they will go to zero and stay ther for a while.

What I do on these is print off a diagram of the computer circuits, then circle the affected modules. In doing so, you can see that they all nearly line up in a row. All are in a loop except the RIM. Possible that the RIM is wigging out, crashing the comm on the others. You'll need to monitor activity on the databus. Often I remove one module at a time until the symptom leaves.

So what you are saying Ric is that you do not think that this is an issue with a bad relay or power supply to the modules. Would that make sense or would it effect more than four modules.

Unless the power supply fed all those modules, then not likely, but possible. Most of the issues I see with databus issues stem from either a bad module pulling the bus down to ground or wiring, causing an open or short.

Can you get a the symptom to occur regularly? If so, clear the codes and see if only a few or one returns. That might help narrow down the module or area.

This vehicle also has 2 splice packs. I've seen problems there before, usually when someone untaped one and messed with it.

Also see if there are any aftermarket devices on the vehicle. Some tap into the databus and can be a source of problems.

Thanks for the input. I had to drive this thing for 25 miles to get it to act up. When it did the whole dash lit up. The charge light is on. The a/c quit working as well as the fuel and temp guage. The trac lite is on, stability control, air bag, and power windows in the front are intermittant. The whole time that It has been here the rear windows do not work. I am going to clear codes and see what happens. It is looking to me like the IPM or the DIM is bad.

As a suggestion, you might want to go straight to the rear windows. They are dead all the time? Both are on the data line. See if you can ping them.

Thanks. I will try that first.

Cleared all codes and could not get into any of the modules. Unplugged both rear door modules and was then able to get into the rest of the modules. Drove it with the rear door modules unplugged and it did not act up. Found broken wiring from the b pillar to the door. repaired that and the left lock works and I can get info from that module. Looked at the right door and almost all the wiring is broken in that door. At this point i contacted the customer to update on the progress and found out that the regulators had broken and the windows were locked in the up position. I disconnected the wiring to the right rear door at this time. Nice to have all the info up front. Probably the same hack that caused the improper movement of the harness that caused the wiring to bend and break. I need to drive this more to see if any problems reoccure. I will post if this cured the problem. Thank for all the input.

Drove the car and all is fine. Customer decided not to install a harness on the right rear door so I left the harness unplugged. Car is FIXED Thanks again for the input and all the help.

Nice work