U0073 code meaning
Control Module Communication Bus A Off
Network system Generic code U00xx codes Check engine light
What U0073 means
U0073 is logged by a module whose own CAN controller has withdrawn from Bus A. Each failed transmission adds eight to its transmit error counter; above 255 the chip goes bus off and may rejoin only after 128 runs of 11 recessive bits (onsemi). GM's 2019 tables flag more than five bus-off events, about 0.06 s, inside a 0.81 s window as Type A with MIL on the first trip, and the ECM suspends lost-communication tests such as U0101 while it is active. Around 2006 GM still reported this state as U0001. A Ford TCM turns the MIL on at once because engine speed is missing. Bulletins trace U0073 to a loose ground (Trax, G103), backed-out terminals in the 6L80 transmission connector and harness rubbing on a cylinder head (Silverado LV3). Expect several warnings, possibly a gearbox held in one gear.
U0073 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0073
- MIL and several cluster warnings at the same time
- Transmission stuck in one gear or shifting harshly
- Gauges fluctuate or drop out briefly
- Lost-communication codes such as U0100 or U0101 in other modules
Common causes of U0073
- Most likelyBus A wires chafed through or shorted to ground in the harness
- PossibleLoose or corroded ground point of a module on Bus A
- PossibleBacked-out or loose terminals, e.g. in the transmission connector
- Less likelyOpen or shorted terminating resistor
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
CAN bus wiringCAN terminating resistorControl module
What each part of U0073 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 73 | The exact fault in that area. |
What to do next
- Note U0073 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0073
What does U0073 mean?
U0073 means "Control Module Communication Bus A Off". U0073 is logged by a module whose own CAN controller has withdrawn from Bus A. It is a generic code, so it means the same on every make.
Is it safe to drive with U0073?
Drive gently and only to a workshop. With U0073 the car can go into limp mode (reduced power) to protect itself.
Will U0073 fail an emissions test?
Yes, it can. U0073 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0073 to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will U0073 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.