U0012Medium Speed CAN Communication Bus (+) Open
- Generic OBD-II code · Network
- How the car detects it
- U0012 reports an interruption of CAN-High, the (+) wire of the medium-speed CAN. Saab's mid-speed GMLAN uses the same two-wire layout as the fast bus, with a terminating resistor between (+) and (-), so a break isolates the modules downstream and alters the resistance seen between the lines. Ford's F-Super Duty illustrates the effect at vehicle level: if connector C408 stays unplugged after the pickup box is removed, MS-CAN traffic is cut and climate control, front controls and headlamp logic stop working. No manufacturer documents U0012 with its J2012 meaning; Alfa Romeo uses U0012-14 and -15 for the up circuit of its DNA selector instead. Check terminals and splices of the medium-speed pair, especially at doors, tailgates and upfitter bodies.
- What you may notice
- Comfort and body modules behind the break inoperative
- Climate, lighting or switch panel functions missing
- Likely causes
- LikelyBody or upfitter connector in the medium-speed (+) path left open
- PossibleCAN-High conductor broken in a door or tailgate harness
- PossibleCorroded or loose CAN-High terminal
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.