Network, generic (extended)

U3505 Control Module Input Power B Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3505 reports that supply input B is too low. In GM's 2016–2019 hybrid tables the electric brake booster treats B as the battery feed of the booster circuit and checks it at several levels: sensor reading under 6 V for 30 s, battery voltage under 9.3 V for 90 s, and quick 0.2 s checks with reduced assist once it falls below 9.3 V (level 1) or 7.5 V (level 2); all Special Type C, no MIL. Body controllers use the code too: GM bulletin PIT5869 (revised as PIT5869A) on 2021–2024 full-size SUVs such as Escalade and Tahoe pairs U3505 with U3018 and B1AA3, warm A/C and the SES light; a shorted circuit to the front console compartment lamp opens fuse F4DR on the BCM's second feed. Check fuse and battery first.

Likely causes

Fuse of feed B blown by a short elsewhere on the circuit
Weak or discharged 12 V battery
Corroded terminal or ground in feed B
Internal measurement or supply path faulty

Symptoms

  • Functions on the second feed missing, e.g. warm A/C
  • Reduced brake assist with warning on booster modules
  • Stored together with U3018

Repair estimate

DifficultyEasyDIY possible
Parts and labour€10–400
Time0.3–2.5 h

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

Parts involved

module power bpower wiringfuse

Related codes

U3506U3504U3507U3018U3007

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.