OBD-II code · Network (extended)
U3503 Control Module Input Power A Circuit Intermittent/Erratic
Intermittent dropouts or noise on input power line A. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.
Is it safe to drive with U3503?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyConnector loose or corroded
- Less likelyGateway module routing CAN messages incorrectly
- Less likelyCAN terminating resistor (120 Ω) drifted out of spec
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–2 h
- Emissions test
- Usually unaffected
- Parts involved
- Module Power A, Power Wiring
Related codes
- U3507Control Module Input Power B Circuit Intermittent/Erratic
- U350BControl Module Input Power C Circuit Intermittent/Erratic
- U3500Control Module Input Power A Circuit Range/Performance
- U3501Control Module Input Power A Circuit Low
- U3502Control Module Input Power A Circuit High
- U3504Control Module Input Power B Circuit Range/Performance
- U3505Control Module Input Power B Circuit Low
- U3506Control Module Input Power B Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.