Network, generic

U0013 Medium Speed CAN Communication Bus (+) Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0013 indicates that CAN-High on the medium-speed bus, the (+) wire, is pulled toward ground. Where this network uses the same differential layout as high-speed CAN, as Saab's terminated mid-speed GMLAN suggests, a grounded CAN-High rules out any dominant bit; onsemi and NXP list this short among those that end all communication. Every node on the segment, usually body, climate and infotainment units, therefore goes quiet together, and the gateway or body controller stores missing-message codes for them. No manufacturer documents U0013 publicly. Powertrain functions on the separate fast bus normally carry on. With the battery off, a resistance of only a few ohms from CAN-High to ground locates the short; typical spots are door boots, seat rails and trim fasteners.

Likely causes

Medium-speed CAN-High insulation damaged against body ground
Wires broken open in a door boot or tailgate grommet
Comfort module transceiver pulling CAN-High down

Symptoms

  • All comfort and infotainment modules fail together
  • Engine and transmission keep working normally

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–700
Time1–5 h

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

Parts involved

can high wirebody control module

Related codes

U0004U0010U0012U0014

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