U007B code meaning
Control Module Communication Bus I Off
What U007B means
U007B is tied to no published manufacturer use; a Bus I only exists on vehicles split into many separate networks. The cause need not sit in the wiring at all. Onsemi describes a node whose transmit pin cannot produce a dominant level: every start-of-frame attempt fails and raises the error counter by eight, after 17 attempts it is error passive and shortly afterwards bus off, although the remaining bus may keep running normally. A damaged transceiver, a supply dip at the module or a cracked solder joint can therefore produce U007B in a single module only. If the code returns after clearing, check that module's power and ground under load and swap it against a known good unit before opening the harness.
U007B at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U007B
- Only the reporting module's functions drop out
- Code returns soon after clearing
Common causes of U007B
- PossibleTransceiver in the reporting module unable to drive the bus
- PossibleWeak supply or ground at the reporting module
- Less likelyShort or open in the Bus I wiring
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Bus i wiringCAN transceiver
What each part of U007B means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7B | The exact fault in that area. |
What to do next
- Note U007B 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 U007B
What does U007B mean?
U007B means "Control Module Communication Bus I Off". U007B is tied to no published manufacturer use; a Bus I only exists on vehicles split into many separate networks. It is a generic code, so it means the same on every make.
Is it safe to drive with U007B?
U007B does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U007B fail an emissions test?
U007B 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 U007B to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U007B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.