U0024 code meaning
Low Speed CAN Communication Bus (-) Open
What U0024 means
U0024 reports an interruption of the (-) line, CAN-Low, of a two-wire low-speed CAN. Under the ISO 11898-3 fault-tolerant scheme this wire idles near 5 V and is pulled toward ground for dominant bits. NXP's TJA1055 counts a broken CAN-Low as failure 2, keeps drivers and termination as they are and goes on receiving differentially; it can flag the break only when the gap separates transmitter and receiver, which makes its error output flicker. Because the network keeps running, the fault often surfaces only as a stored code in modules beyond the break. Places where wires flex, such as door or tailgate transitions, are obvious suspects. The single-wire GM low-speed GMLAN has no (-) line, so the code has no meaning there. No manufacturer documents U0024 publicly.
U0024 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 U0024
- Typically no symptom, code found during a scan
- Comfort functions behind the break react sluggishly or sporadically
Common causes of U0024
- Most likelyCAN-Low wire broken in a door or tailgate harness
- PossibleCAN-Low terminal backed out of its connector
- PossibleCorroded CAN-Low contact after water entry
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 low wireModule connector
What each part of U0024 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 24 | The exact fault in that area. |
What to do next
- Note U0024 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 U0024
What does U0024 mean?
U0024 means "Low Speed CAN Communication Bus (-) Open". U0024 reports an interruption of the (-) line, CAN-Low, of a two-wire low-speed CAN. It is a generic code, so it means the same on every make.
Is it safe to drive with U0024?
U0024 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0024 fail an emissions test?
U0024 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 U0024 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U0024 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.