Network, generic

U0041 Vehicle Communication Bus B (+) High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0041 means the (+) wire of Vehicle Communication Bus B sits at too high a voltage, typically because it touches a battery or 5 V supply. For a high-speed-type CAN this is CAN-High, and NXP classes a short of CAN-High to battery or to VCC as a hidden failure: frames keep flowing, so only a transceiver with bus diagnosis, such as the TJA1043, reports it. On a fault-tolerant low-speed CAN NXP's TJA1055 reacts in two steps after time-outs and finally switches off its CANH driver, running on CAN-Low alone. Either way the vehicle often behaves normally, and the code may sit in memory long before anything fails. No manufacturer documents U0041 publicly. A reading near supply voltage on CAN-High against ground confirms it; check for chafing against feed wires and moisture in connectors.

Likely causes

(+) wire chafed against a battery or 5 V feed
Moisture in a connector bridging the (+) wire to a supply pin
Faulty transceiver driving the (+) line high

Symptoms

  • Often no noticeable symptom, code found during a scan
  • Sporadic warnings from one module

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–700
Time1–5 h

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

Parts involved

bus b wiringbus b transceiver

Related codes

U0032U0037U0039U0040U0044U0050

References: nxp.com, nxp.com, onsemi.com.