OBD-II code · Network
U0074 Control Module Communication Bus "B" Off
A control module has shut its bus B interface off because the bus is non-functional. Bus B is typically a secondary CAN segment (often body or chassis) and a failure disables all modules connected to it.
Is it safe to drive with U0074?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyBus B line shorted to supply or ground
- PossibleOne failing module pulling the bus down
- Less likelyGateway module routing CAN messages incorrectly
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
- 1–8 h
- Emissions test
- Usually unaffected
- Parts involved
- Can Bus Wiring, Can Terminating Resistor, Control Module
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.