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Intermittent no starting and charging
Posted to Technical Discussion Forum on 2/4/2025 28 Replies

The car was originally brought in for a no charge situation. We ran a battery and charging system test and found the alternator not charging (alternator failed by local parts house bench test). We replaced the alternator. We released the vehicle to the customer.

2 weeks later and came back with the same complaint and battery charge light was on. We removed the alternator and did another bench test which it had passed. We re-installed alternator in the vehicle, did a relearn alternator and did a scanner command for alternator on and off and it tested fine. We pulled the codes and had no code for the engine, but a couple body control modules for the passenger glovebox. Cleared all codes and returned the car to the customer.

Body Module control: B32OA U0155 U155 lost communication with radio B1850 Driver seat lumbar

2 weeks later the customer had the same complaint of no power, but the battery charging light was not on. There was an engine code PO621 generator L. Hook up scanned tool command generator L. The alternator was working fine removed and did a bench test, tested fine. Pulled all codes there were a few body control module codes and a U0155. Tried to duplicate the alternator not working we weren't able to. Started to do wiggle and connection tests for the computer and fuse box connections. Tested the wiring circuit for generator L. The wiring harness between alternator and pcm seems to be okay. There are no shorts or openings. Came in on a Monday morning and the battery was dead. Suspect a draw or a computer not sleeping, but are unable to duplicate. A couple days later the same thing occurred but we found no draw. went to start the vehicle battery voltage was low, the vehicle cranked and started with no dash light or instrument cluster. Battery voltage low we recharged battery and restarted car, car started and all light worked properly and no new codes. We parked the car and a few days later the battery was dead, we jumped started, the car had no dash light and drove the car into the shop. We recharged the battery, started up and ran code tests on new codes. The charging system passed the test suspect and intermittent battery problem, replaced the old battery with a new battery. The new battery learned the procedure. We had to start the car a few later and the car won't start.

We pulled the codes and have the same codes plus new codes which are injector codes. Did pin testing have no 5 volt reference for the injector coming out of the computer the ECM itself. WAlso found we had no power coming out of the ECM relay, bypassed the relay and have power for computer and injector fuses now. Still no start. Tested wiring harness from relay to ECM wiring tested good. Per diagnostic flow cart replace ECM is recommended et new ECM installed learn key security lig goes off. ECM is working properly now, still no start and the same codes including the injectors. Codes: Engine P0621 Generator L Po118 Engine Coolant Temp Antilock Brakes C0267 -Low Brake Fluid C0561-System Disabled C0899- Device #1 Voltage Low U0100- Lost communication with EMC/PCM Airbag U155- No can bus communication with gateway Body Control Module B2705- Gearshift unlock short to ground B1395- Device voltage reference output 1 B1529 -Device Voltage Reference Output 5 U0155- Lost Communication with ECM/PCM Injector code 201203 P0201

P0202 P0203 P0204 P0205 P0206 Door Switch Passenger B320A- Front door window Parking Brake Control Module C0561- System disabled Transfer Case U0100- Lost Communication with ECM OBDI P0201 cylinder 1 injector "A" Circuit The car will crank with no start, no dash lights.

Steve Wylie
Owner
Bob's Auto & Towing
Corvallis, Oregon, USA

28 Replies Received (View Replies)

 

car Vehicle Data

2012 Cadillac CTS Performance 3.6L

Engine3.6 L
Trans6-speed Automatic (Electronic)

car Vehicle Data

2012 Cadillac CTS Performance 3.6L

Engine3.6 L
Trans6-speed Automatic (Electronic)