U351C code meaning
High Voltage System Interlock Circuit D High
Network system Generic code U35xx codes Check engine light
What U351C means
U351C is stored when loop D carries more voltage than its present state allows. GM's high check for loop A, P0A0D, shows why both states are tested: with the source commanded to 0 V, more than 24 % of 5 V counts as a failure, five times in eight samples; with the source at 5 V the limit is 44 %, four times in six. A loop that fails to fall when its source switches off reveals foreign voltage even if it looks normal while fed. No maker lists U351C. Likely are a loop wire touching a 12 V feed, a source that no longer turns off, or a bad repair splice. Readiness is withheld until the loop is clean.
U351C at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U351C
- Vehicle does not reach ready mode
- Fault returns immediately after clearing
- Other 12 V consumers may show faults if a supply wire is involved
Common causes of U351C
- Most likelyLoop D wire in contact with a 12 V supply line
- PossibleSource driver in the controller no longer switches off
- Less likelyEarlier repair splice joined the loop to a wrong wire
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hvil loop dHvil wiring
What each part of U351C means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 1C | The exact fault in that area. |
What to do next
- Note U351C 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 U351C
What does U351C mean?
U351C means "High Voltage System Interlock Circuit D High". U351C is stored when loop D carries more voltage than its present state allows. It is a generic code, so it means the same on every make.
Is it safe to drive with U351C?
Drive gently and only to a workshop. With U351C the car can go into limp mode (reduced power) to protect itself.
Will U351C fail an emissions test?
U351C 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 U351C to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U351C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.