U0022 code meaning
Low Speed CAN Communication Bus (+) Low
What U0022 means
U0022 indicates a ground short on CAN-High, the positive conductor of a dual-wire low-speed CAN. In the fault-tolerant design of ISO 11898-3, where CAN-High idles at about 0 V and only rises for dominant bits, a ground short simply takes that rise away. NXP's TJA1055 lists CAN-High to ground as failure 5 and keeps transmitting and receiving differentially, since its receiver threshold is chosen so that reception stays correct in this case as well. The network therefore keeps working, and the driver often notices nothing apart from the stored code. On GM's single-wire low-speed GMLAN the (+)/(-) naming does not fit. No manufacturer documents U0022 publicly. With the battery disconnected, a reading near zero ohms from CAN-High to ground confirms the short; trim screws and seat rails are typical culprits.
U0022 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0022
- Frequently no symptom besides the stored code
- Rare sporadic comfort function faults
Common causes of U0022
- Most likelyCAN-High insulation chafed through against body ground
- PossibleWire pierced by a trim screw or trapped under a seat rail
- Less likelyInternal transceiver fault pulling CAN-High low
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Low speed CAN wiringCAN high wire
What each part of U0022 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 22 | The exact fault in that area. |
What to do next
- Note U0022 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 U0022
What does U0022 mean?
U0022 means "Low Speed CAN Communication Bus (+) Low". U0022 indicates a ground short on CAN-High, the positive conductor of a dual-wire low-speed CAN. It is a generic code, so it means the same on every make.
Is it safe to drive with U0022?
U0022 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0022 fail an emissions test?
U0022 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 U0022 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U0022 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.