Network, generic

U0024 Low Speed CAN Communication Bus (-) Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

CAN-Low wire broken in a door or tailgate harness
CAN-Low terminal backed out of its connector
Corroded CAN-Low contact after water entry

Symptoms

  • Typically no symptom, code found during a scan
  • Comfort functions behind the break react sluggishly or sporadically

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–500
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

low speed can wiringcan low wiremodule connector

Related codes

U0006U0019U0021U0025U0026

References: nxp.com, law.cornell.edu, saabwisonline.com.