U3515 code meaning
High Voltage System Interlock Circuit C
Network system Generic code U35xx codes Check engine light
What U3515 means
U3515 is the general fault of a third interlock loop, circuit C. Such a loop exists where one or two are not enough: Caterpillar's patent for battery machines forms a separate interlock circuit from each battery group with its disconnect and contactor pair, and Samsung SDI mentions designs with more than two independent loops for parts inside the pack. Volvo couples two loops through an isolated relay so that a fault in one opens the other, which is why codes for several loops can be logged together. Which component a manufacturer wires into loop C is not documented publicly for any vehicle. U3515 applies when loop C fails without a more specific low, high or performance result; HV power remains off until the loop is closed again.
U3515 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 U3515
- No ready mode, HV system switched off
- Interlock codes for more than one loop stored together
- Charging blocked
Common causes of U3515
- Most likelyConnector or cover belonging to loop C opened during work and not refitted correctly
- PossibleInterlock harness of loop C damaged
- PossibleFault in a coupled loop opening loop C as well
- Less likelyMonitoring module unable to drive or read loop C
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hvil loop cHv connectors
What each part of U3515 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 15 | The exact fault in that area. |
What to do next
- Note U3515 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 U3515
What does U3515 mean?
U3515 means "High Voltage System Interlock Circuit C". U3515 is the general fault of a third interlock loop, circuit C. It is a generic code, so it means the same on every make.
Is it safe to drive with U3515?
Drive gently and only to a workshop. With U3515 the car can go into limp mode (reduced power) to protect itself.
Will U3515 fail an emissions test?
U3515 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 U3515 to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U3515 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.