U351D code meaning
High Voltage System Interlock Circuit E
Network system Generic code U35xx codes Check engine light
What U351D means
U351D covers a disturbed fifth interlock loop, circuit E, where the module cannot narrow the fault down. Five loops arise naturally if every protected housing gets its own circuit. A GM patent describes this: each high-voltage enclosure has a functional interlock tied to its access point, and the low-voltage signal inside only gets through while that opening is closed. Removing a cover is thus noticed by the circuit of that very housing. Which enclosure belongs to loop E is not published. Check covers, lids and their screws first, then the plugs of the housings involved; high voltage stays off until loop E is closed.
U351D 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 U351D
- No ready mode after work on a high-voltage component
- High-voltage warning in the instrument cluster
Common causes of U351D
- Most likelyCover of a high-voltage housing on loop E not fitted or not fully tightened
- PossibleInterlock contact or bridge in the cover bent or broken
- PossibleLoop E wiring damaged between housings
- Less likelyEvaluating controller faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hvil loop eHv connectors
What each part of U351D means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 1D | The exact fault in that area. |
What to do next
- Note U351D 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 U351D
What does U351D mean?
U351D means "High Voltage System Interlock Circuit E". U351D covers a disturbed fifth interlock loop, circuit E, where the module cannot narrow the fault down. It is a generic code, so it means the same on every make.
Is it safe to drive with U351D?
Drive gently and only to a workshop. With U351D the car can go into limp mode (reduced power) to protect itself.
Will U351D fail an emissions test?
U351D 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 U351D to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U351D clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.