U0079 code meaning
Control Module Communication Bus G Off
What U0079 means
No manufacturer documents U0079 publicly, so what Bus G is depends entirely on the vehicle. The code belongs to the bus-off family: the controller of the reporting module has collected enough transmit errors to stop sending in order to protect the other nodes. That sets it apart from U0089, the general Bus G fault, and from lost-communication codes such as U0100, which other modules store once they no longer hear the silent one. CARB requires that missing communication of digital inputs and outputs be detected and stored under its own code, which is why a module records its own disconnection. Read all modules first: if only one holds U0079, its transceiver, supply or connector is suspect; if several do, look at the Bus G wiring and termination.
U0079 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0079
- Functions of the reporting module unavailable
- Lost-communication codes in other modules
Common causes of U0079
- PossibleShort between the Bus G wires or to ground
- PossibleFaulty transceiver in the reporting module
- Less likelySupply or ground dropouts at the reporting module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Bus g wiringCAN transceiver
What each part of U0079 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 79 | The exact fault in that area. |
What to do next
- Note U0079 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 U0079
What does U0079 mean?
U0079 means "Control Module Communication Bus G Off". No manufacturer documents U0079 publicly, so what Bus G is depends entirely on the vehicle. It is a generic code, so it means the same on every make.
Is it safe to drive with U0079?
U0079 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0079 fail an emissions test?
U0079 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0079 to fix?
Difficulty: hard. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will U0079 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.