U3505Control Module Input Power B Circuit Low
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Functions on the second feed missing, e.g. warm A/C
- Reduced brake assist with warning on booster modules
- Stored together with U3018
- Likely causes
- LikelyFuse of feed B blown by a short elsewhere on the circuit
- LikelyWeak or discharged 12 V battery
- PossibleCorroded terminal or ground in feed B
- RareInternal measurement or supply path faulty
- Repair
- Easy · Often possible to do yourself.Typical cost: €10 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.