Got these codes, has anyone ran into this problem and know how to fix it?

everything works with the key on, reduce engine power and service vehicle soon message pops up.
when trying to start dash lights would shut off and restart. Door locks and window switch would not work either.

If you disconnect the battery and reinstall the vehicle would start back up, if you leave it sitting the codes would come back and no start.

 

Found this on one of Bill Curlee's responses to an old post.
It might be something to look into if your battery is older, you also
might want to check the connections to the battery.

"Something else that can cause the U series codes is a weak or aged battery. When you crank the engine, if the battery voltage drop down too low,,, it will cause modules to shutdown and set a U series DTC."

 

The battery is Fairly new, got it maybe 4 days ago. How likely would it be for the BCM to be bad?

 

Sorry cant help you there. I do know these cars get crusty grounds that cause all
kinds of weird problems. Maybe someone that knows more than me will chime in.

 

No worries thanks for replying. I did go around and check all the ground, . All of them seem fine.

 

Keep searching with google it works better than the forum search. Also remember that new doesn't
always mean good, you may want to take the battery back where you got it and have them test it.
Good luck, electrical problems can be a bear.

 

You need a new battery

 

I’ll take the battery back tomorrow and have them re-tested it, Thanks.

 

Yes, first have the battery LOAD tested.

If the battery is good, make sure that the battery terminal connections are clean and tight, FSM says 11 foot pounds.

With the above complete and a confirmed good battery, what does the instrument cluster voltage meter say, ignition key on run-- BEFORE attempting to start? Should be around 12.6 volts. If the battery tested good and the instrument cluster voltage is low, I would suspect a bad ignition switch. Another culprit is the wiring connection to the driver side door.

Pull the rubber accordion which covers the wiring going into the door and inspect the multi prong connector going into the door. There have been instances where your car's symptom have been a result of a bad connection in the connector to the door. Passenger side much less frequently because the passenger door does not get opened/ closed as often.

How did you check the grounds? Disassemble, clean and dielectric grease before tightening. Just a visual check does not tell you much. A bad ground often LOOKS fine but the ground can be bad because of corrosion between the connection of the wire pack wire to ground stud or wire to ground stud.

One indicator of a failing ignition switch is that a shut down and restart results in no symptoms or different symptoms. Next start, something else or the same as prior.

Report back.

 

The BCM maybe bad, one symptom of a bad BCM is having to disconnect the battery to get the car to crank. There are BCM rebuilders that you can send your BCM to, one of them is G7 computers.