OBD-II code · Network (extended)
U3020 Control Module Wake-up Circuit B High
Wake-up signal B voltage above expected range. 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 U3020?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyWiring shorted to battery
- 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
- Wakeup Circuit B, Wakeup Wiring
Related codes
- U301CControl Module Wake-up Circuit A High
- U301DControl Module Wake-up Circuit A Performance
- U301EControl Module Wake-up Circuit B/Open
- U301FControl Module Wake-up Circuit B Low
- U3021Control Module Wake-up Circuit B Performance
- U3022Ignition Input Accessory/Off
- U3023Control Module Input Power Circuit A - Ignition Input On/Start Circuit Correlation
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.