U3505 code meaning
Control Module Input Power B Circuit Low
What U3505 means
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.
U3505 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3505
- Functions on the second feed missing, e.g. warm A/C
- Reduced brake assist with warning on booster modules
- Stored together with U3018
Common causes of U3505
- Most likelyFuse of feed B blown by a short elsewhere on the circuit
- Most likelyWeak or discharged 12 V battery
- PossibleCorroded terminal or ground in feed B
- Less likelyInternal measurement or supply path faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Module power bPower wiringFuse
What each part of U3505 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 05 | The exact fault in that area. |
What to do next
- Note U3505 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U3505
What does U3505 mean?
U3505 means "Control Module Input Power B Circuit Low". U3505 reports that supply input B is too low. It is a generic code, so it means the same on every make.
Is it safe to drive with U3505?
Drive gently and only to a workshop. With U3505 the car can go into limp mode (reduced power) to protect itself.
Will U3505 fail an emissions test?
U3505 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U3505 to fix?
Difficulty: easy. A typical repair takes 0.3 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U3505 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.