U3023 code meaning
Control Module Input Power Circuit A - Ignition Input On/Start Circuit Correlation
Network system Generic code U30xx codes Check engine light
What U3023 means
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.
U3023 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3023
- MIL on, often with several other codes from the same module
- Engine stalls or does not start
- Transmission faults when the TCM stores it
Common causes of U3023
- Most 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
- Less likelyFaulty voltage sensing inside the module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Module power aIgnition input
What each part of U3023 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 23 | The exact fault in that area. |
What to do next
- Note U3023 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U3023
What does U3023 mean?
U3023 means "Control Module Input Power Circuit A - Ignition Input On/Start Circuit Correlation". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with U3023?
Drive gently and only to a workshop. With U3023 the car can go into limp mode (reduced power) to protect itself.
Will U3023 fail an emissions test?
U3023 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U3023 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U3023 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.