U351A code meaning
High Voltage System Interlock Circuit D Performance
Network system Generic code U35xx codes Check engine light
What U351A means
U351A says that loop D returns a signal, but not the one the module sent out. Many designs feed the loop with pulses rather than a steady level. In a Corun battery patent a microcontroller sends a 0 to 5 V square wave at 100 Hz with half on, half off through the interlock switches of pack, motor controller and vehicle controller, and treats the loop as sound only if frequency, on-time and amplitude return unchanged. A rounded, shifted or weakened pattern hints at contact resistance, moisture or coupled interference rather than a clean break. No maker documents U351A. High voltage may drop out without warning.
U351A at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U351A
- Sudden loss of high-voltage power while driving or charging
- Fault appears after rain, washing or on rough roads
- Restart sometimes possible after switching off and on
Common causes of U351A
- Most likelyCorroded or worn interlock contacts adding resistance to loop D
- PossibleMoisture in a low-voltage connector of the loop
- Less likelyLoop wiring routed too close to switching high-voltage cables
- Less likelySignal input of the evaluating 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 d
What each part of U351A means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 1A | The exact fault in that area. |
What to do next
- Note U351A 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 U351A
What does U351A mean?
U351A means "High Voltage System Interlock Circuit D Performance". U351A says that loop D returns a signal, but not the one the module sent out. It is a generic code, so it means the same on every make.
Is it safe to drive with U351A?
Drive gently and only to a workshop. With U351A the car can go into limp mode (reduced power) to protect itself.
Will U351A fail an emissions test?
U351A 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 U351A to fix?
Difficulty: hard. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will U351A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.