Network, generic

U0048 Vehicle Communication Bus C (+) Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0048 stands for an open (+) wire on Vehicle Communication Bus C, CAN-High where Bus C is a CAN. Deutz places the code on CAN 4 of its EMR L1 engine controller, listed for main and secondary ECU as an open circuit on that channel, just as U0039 covers CAN 3. Electrically, an interrupted CAN-High wire splits a high-speed CAN into islands that keep working internally; NXP points out that transceiver diagnosis cannot report such a break, so the controller relies on missing messages. A fault-tolerant low-speed transceiver such as NXP's TJA1055 rides through the same break with its drivers left active. Expect lost-communication entries for nodes located past the interruption. No car maker documents U0048 publicly. Check connector seating, crimp terminals and harness flex points first.

Likely causes

(+) wire of Bus C broken at a flex point or splice
Loose crimp or backed-out terminal
Connector not fully seated

Symptoms

  • Modules on the far side of the break unreachable
  • Lost-communication codes in several modules

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–700
Time0.5–5 h

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

Parts involved

bus c wiringmodule connector

Related codes

U0030U0039U0046U0049U0050U0051

References: serdia.deutz.com, serdia.deutz.com, nxp.com, nxp.com.