Network, generic

U009C Vehicle Communication Bus I Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U009C reports that Vehicle Communication Bus I carries traffic, but not at the quality the module expects. U009C has not been documented in public by any manufacturer. The causes lie in signal integrity rather than a hard fault. Texas Instruments ties the possible bus length to the data rate, roughly 40 m when running at 1 Mbit/s and 100 m at half that rate, and names cable bandwidth and intersymbol interference as the limits; repairs with long added wire or untwisted cable eat into that margin. TI cites the standard's twisted pair with 120 ohms impedance. CAN detects such distortion as protocol errors: Wikipedia explains that after five identical bits the sender adds one of the inverse value, and six identical bits in a row count as an error, prompting a repeat.

Likely causes

Loose contact causing bit errors
Repair with untwisted or overly long wire
Missing or wrong termination

Symptoms

  • Brief dropouts of functions on Bus I
  • Delayed reactions of displays or controls

Repair estimate

DifficultyHardWorkshop job
Parts and labour€50–800
Time0.5–5 h

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

Parts involved

bus i wiringmodule connector

Related codes

U007BU0093U009BU009E

References: ti.com, en.wikipedia.org, law.cornell.edu.