U3527 code meaning
High Voltage System Interlock Circuit G Low
Network system Generic code U35xx codes Check engine light
What U3527 means
U3527 sets when the level on loop G drops below what the module expects. When several controllers watch interlock lines, the reporting unit already narrows the search. A Mercedes service bulletin on the 243 model series shows this with loop A codes: the DC charging unit and the AC charger each store a ground-short code, the battery management a short to positive, and the PTC heater has a separate code. For loop G, start measuring at the controller storing U3527, follow its section outward and compare the codes in the other units. No maker publishes U3527. While the low reading persists, the contactors behind loop G stay locked.
U3527 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3527
- Vehicle does not become ready, or charging is refused
- Interlock codes in more than one control unit
Common causes of U3527
- Most likelyLoop G wire cut or chafed to ground near a control unit
- PossiblePlug in the section of the reporting unit not connected
- Less likelyLoop source of the reporting controller failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hvil loop gHvil wiring
What each part of U3527 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 27 | The exact fault in that area. |
What to do next
- Note U3527 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 U3527
What does U3527 mean?
U3527 means "High Voltage System Interlock Circuit G Low". U3527 sets when the level on loop G drops below what the module expects. It is a generic code, so it means the same on every make.
Is it safe to drive with U3527?
Drive gently and only to a workshop. With U3527 the car can go into limp mode (reduced power) to protect itself.
Will U3527 fail an emissions test?
U3527 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 U3527 to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will U3527 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.