Network, generic

U0002 High Speed CAN Communication Bus Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U0002 stands for impaired rather than lost traffic on the high-speed CAN, and makers fill the slot in different ways. GM/Saab sets it when a supervised periodic message, which also tells the receiver that its sender is alive, has not shown up within the 250 ms supervision time; the receiver then carries on with a default value. FCA calls U0002 CAN C Bus Off Performance: a reflash for the 2013 Ram 2500/3500 6.7 L diesel PCM changed it from a one-trip to a two-trip MIL fault, whereas the 2024-26 Dodge Charger steering column module stores it without MIL because dips in supply voltage lasting about 40 ms trip a software bug. In contrast to U0001 the bus mostly keeps working, so complaints come and go: sporadic warnings or single functions dropping out briefly.

Likely causes

Intermittent contact at connectors or splices of the bus pair
Module software reacting to short voltage dips (reflash available)
Weak battery or poor ground causing brief module resets
Electrical interference from retrofitted devices on the bus

Symptoms

  • Warning lamps that appear and disappear again
  • Single functions briefly unavailable
  • Code stored as history without a current fault

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–1,000
Time0.5–6 h

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

Parts involved

can bus wiringcontrol module

Related codes

U0001U0011U0073U0100

References: saabwisonline.com, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.