Network, generic (extended)

U3501 Control Module Input Power A Circuit Low

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modePossible

U3501 reports that supply A of a module is below its permitted range. GM's electric brake booster (BSC2) in the 2016–2019 hybrid OBD tables runs two checks: the CAN/logic supply under 7.5 V for 0.09 s, and the internal sensor for the module supply under 4.9 V for 0.2 s, a level below the point where the hardware should already have shut down. Both are Special Type C, so no MIL. The weight of the code lies elsewhere: GM lists U3501 among the conditions that suspend many other booster tests, because motor and sensor checks are meaningless without proper supply. It passes after 30 s with ignition on. Usual causes are a weak or discharged battery, a deep dip while cranking, a corroded fuse or terminal on the feed, or a bad ground.

Likely causes

Weak or discharged 12 V battery

Deep voltage dip during engine start

Corroded fuse, terminal or ground in the A feed

Internal supply stage of the module faulty

Symptoms

Module resets or drops off the network at low voltage
Other self-tests of the module suspended
Warning lamp for the affected system, usually without MIL

Repair estimate

DifficultyEasyDIY possible

Parts and labour€10–300

Time0.3–2 h

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

Parts involved

module power apower wiringfuse

Related codes

U3502 U3500 U3503 U3006 U3505

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