U0073
Control Module Communication Bus A Off
Communication / network
Generic OBD-II
High
What it means
U0073 means the ECM has shut down communication bus "A" because it detected too many errors on the network. When the bus goes off, control modules can no longer share data, which often lights up several warning lamps at once and can trigger limp mode or a no-start. It usually points to a wiring short, a bad connector, or one failed module disrupting the whole network.
High
Can I keep driving? Risky — a bus-off fault can stop control modules talking to each other, which may bring on warning lights, limp mode, or even a no-start; have it diagnosed before driving far.
Common symptoms
What you'll notice
- Multiple warning lights on (ABS, traction, airbag, check-engine)
- Several modules unresponsive to a scan tool
- Limp mode or reduced power
- Possible no-start or intermittent stalling
- Erratic gauges or disabled features
Common causes
Most likely first
- Short to power or ground on the CAN bus wiring (most common)Likely
- Damaged or corroded connector on the communication busCommon
- A single failed module dragging the whole bus downCommon
- Low battery or charging voltage upsetting the networkLess often
- Failed gateway module or ECM/PCMLess often
How to diagnose & fix
Work through it in order
- Scan all modules and note which ones have dropped off the bus.
- Check battery and charging voltage first — low voltage often trips network codes.
- Inspect CAN bus wiring and connectors for shorts, corrosion, or damage.
- Isolate a suspect module by disconnecting modules one at a time to see if the bus recovers.
- If wiring and modules check out, suspect the gateway or ECM. Clear and retest.
FAQ
Quick answers
Is it safe to drive with U0073?+
Not really. With modules off the bus you can lose safety systems, drop into limp mode, or fail to start — get it diagnosed before relying on the car.
Can I just clear U0073?+
It will usually come straight back while the bus is down. Find and fix the shorted wire or failed module, then clear it.
Related codes
Often seen with U0073
Read & clear U0073 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX