U3021Control Module Wake-up Circuit B Performance
- Generic OBD-II code · Network
- How the car detects it
- U3021 is the plausibility code for wake-up line B: the wire is neither open nor shorted, but the wake signal arrives at the wrong time or does not match what other inputs say. No manufacturer documents U3021 publicly. The closest published logic is Ford's U301D for line A in the 2019 Fusion Energi battery module, which fails when the charge wake-up is still low although the charger output voltage is already in the window for closing the contactors. Chrysler's powertrain counterpart P06E4, wake-up circuit performance, appears in 2024 Jeep Wrangler 4xe bulletins (e.g. 21-017-24) that cure it with new module software. Both cases point the same way: a performance fault on a wake line is often a timing question between two modules and is more often solved by a software update than by new wiring.
- What you may notice
- Warning lamp or message after a wake event, e.g. after charging
- Function works, but the code returns sporadically
- Likely causes
- LikelySoftware in sender or receiver judging the wake timing wrongly
- PossibleSource on line B raising or dropping its signal late
- RareContact resistance on line B slowing the level change
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €0 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.