U0033 code meaning
Vehicle Communication Bus A (-) Open
What U0033 means
U0033 reports an interruption of the (-) wire of Vehicle Communication Bus A; on a dual-line CAN like the sensor/hybrid CAN Audi lists as Bus A, that is CAN-Low. As with U0030, the network falls apart into pieces that can no longer hear each other, and NXP stresses that a standard high-speed transceiver has no means of detecting an open wire on its own. The control module infers the fault indirectly, for example from expected messages that stop arriving or from rising error counters, so the code often appears next to lost-communication entries for modules beyond the break. No manufacturer documents U0033 publicly. With the battery disconnected, a resistance between (+) and (-) that differs from the normal termination value hints at the break; check recently separated connectors first.
U0033 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 U0033
- Modules beyond the break stop responding
- Lost-communication codes stored alongside
Common causes of U0033
- Most likely(-) wire of Bus A broken in the harness
- PossiblePushed-back or corroded terminal in a connector
- PossibleConnector not reconnected after a repair
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Bus a wiringBus a terminatorModule connector
What each part of U0033 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 33 | The exact fault in that area. |
What to do next
- Note U0033 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 U0033
What does U0033 mean?
U0033 means "Vehicle Communication Bus A (-) Open". U0033 reports an interruption of the (-) wire of Vehicle Communication Bus A; on a dual-line CAN like the sensor/hybrid CAN Audi lists as Bus A, that is CAN-Low. It is a generic code, so it means the same on every make.
Is it safe to drive with U0033?
U0033 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0033 fail an emissions test?
U0033 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 U0033 to fix?
Difficulty: hard. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will U0033 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.