OBD-II code · Network
U0033 Vehicle Communication Bus A (-) Open
The communication bus A low-side line (CAN-L) is open — broken wire, unplugged connector, or terminator missing.
Is it safe to drive with U0033?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyCAN-L wire broken or unplugged
- 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
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–5 h
- Emissions test
- Usually unaffected
- Parts involved
- Bus A Wiring, Bus A Terminator
Related codes
- U0051Vehicle Communication Bus C (-) Open
- U0069Vehicle Communication Bus E (-) Open
- U008EVehicle Communication Bus G (-) Open
- U0097Vehicle Communication Bus H (-) Open
- U0030Powertrain Sensor Data Bus
- U0031Vehicle Communication Bus C (+) Open
- U0032Vehicle Communication Bus A (+) High
- U0034Vehicle Communication Bus A (-) Low
- U0035Vehicle Communication Bus A (-) High
- U0036Vehicle Communication Bus A (-) shorted to Bus A (+)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.