U3023Control Module Input Power Circuit A - Ignition Input On/Start Circuit Correlation
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U3023 means a module sees clearly different voltages on its permanent battery feed A and its switched run/crank input while both should be live. GM's 2025 engine and transmission control modules (25OBDG04B, 25OBDG03B and others) run this check once a battery is detected, run/crank is active and the starter is not engaged: a difference above 3 V in 40 of 50 samples fails it, in some ECM variants 50 of 63. The TCM entries are Type A and most ECM entries Type B, both with MIL; one 2025 ECM list (25OBDG04A) keeps it as Type C without MIL. GM bulletin 24-NA-124 shows a typical cause on 2020–2025 Silverado and Sierra 2500/3500: the ECM harness rubs through at the driver-side upper control arm bracket, giving U3023 with P2534, P0700 and others, a lit MIL, a stall or a no-start; the harness is repaired and tied away from the bracket.
- What you may notice
- MIL on, often with several other codes from the same module
- Engine stalls or does not start
- Transmission faults when the TCM stores it
- Likely causes
- LikelyModule harness chafed against a bracket, interrupting feed or ignition wire
- PossibleFaulty run/crank relay or fuse feeding the ignition input
- PossibleVoltage drop on the battery feed from a loose terminal or corroded fuse
- RareFaulty voltage sensing inside the module
- Repair
- Medium · Often possible to do yourself.Typical cost: €20 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.