U0073: Control module communication bus A off
A control unit can no longer use data bus A, as if the network were down. Usually a short in the wiring, a connector or a faulty module.
| Code | U0073 |
|---|---|
| System | Communication network |
| Group | U00xx, Communication buses |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What U0073 means
The car’s control units communicate over data networks called buses. This code means bus A has gone out of service for the unit that stored it: it cannot send or receive messages. Which bus is A (normally a CAN bus) is set by each manufacturer.
Most common causes
- Weak battery or loose terminals
- Bus wires shorted together, to earth or to a live feed
- A control unit connector wet, corroded or with bent pins
- A faulty module shorting the network
- Aftermarket accessory interfering with the bus
Symptoms
- Several warning lights on at once
- Several lost communication codes
- Car may not start or may go into limp mode
- Instrument cluster readings not working
Can you drive with U0073?
With care If the car works normally, you can drive carefully to a garage. If brakes, steering or gearbox misbehave, or many warning lights come on, do not drive and call for assistance.
Open the bonnetthe in-depth explanation
How to check it
Check the battery and its terminals before anything else. Note every U code that appears: the module missing from the scan, or the one with the most faults, is usually close to the problem.
How to read and clear U0073 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see U0073 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- U0069 The vehicle communication bus E (low line) has a broken or disconnected wire
- U0070 The vehicle communication bus E (low line) gives a lower signal than normal
- U0071 The vehicle communication bus E (low line) gives a higher signal than normal
- U0072 The negative line of VAN data bus E has a short circuit to its positive line
- U0079 One of the car’s communication networks has gone down
- U0080 The vehicle communication bus F is not working properly
- U0081 The vehicle communication bus F gives readings outside the normal range
- U0082 The vehicle communication bus F has a broken or disconnected wire
- U0001 High speed CAN communication bus
What does code U0073 mean?
The car’s control units communicate over data networks called buses. This code means bus A has gone out of service for the unit that stored it: it cannot send or receive messages. Which bus is A (normally a CAN bus) is set by each manufacturer.
Can you drive with U0073?
If the car works normally, you can drive carefully to a garage. If brakes, steering or gearbox misbehave, or many warning lights come on, do not drive and call for assistance.
How do you clear U0073?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, U0073 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
