Network, generic (extended)

U3506 Control Module Input Power B Circuit High

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3506 reports overvoltage on supply input B. In GM's electric brake booster (2016–2019 hybrid OBD tables) three checks feed this code: battery voltage of the booster circuit above 17 V for 90 s, the supply of the internal motor driver above 18 V for 1.1 s, and battery voltage above 16.5 V for 1.1 s, at which booster performance is cut back. All are Type B, MIL after two trips; passing takes 90 s with ignition on. The graded limits reveal the idea: brief excursions are tolerated, lasting ones or those that put the power stage at risk are not. Check the charging voltage at idle with loads switched on first, then external chargers, jump starters and loose battery terminals that produce voltage spikes.

Likely causes

Charging voltage too high from regulator or DC/DC converter
Jump starter or charger delivering excessive voltage
Loose battery terminal causing spikes
Faulty measurement of feed B in the module

Symptoms

  • MIL after two trips
  • Reduced assist of the supplied power stage
  • Overvoltage codes in further modules

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–700
Time0.3–2.5 h

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

Parts involved

module power bcharging system

Related codes

U3505U3504U3507U3502U350A

References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.