Network, generic (extended)

U3527 High Voltage System Interlock Circuit G Low

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Loop G wire cut or chafed to ground near a control unit
Plug in the section of the reporting unit not connected
Loop source of the reporting controller failed

Symptoms

  • Vehicle does not become ready, or charging is refused
  • Interlock codes in more than one control unit

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,200
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hvil loop ghvil wiring

Related codes

U3525U3526U3528U3523P0A0C

References: static.nhtsa.gov, law.cornell.edu.