Network, generic

U0083 Vehicle Communication Bus F (+) Low

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modePossible

U0083 means the (+) line of Vehicle Communication Bus F is held too low, normally by a short to ground. On FlexRay, which Audi links to Bus F, the line is bus plus (BP). NXP builds its TJA1081B to survive such a short and lists short-circuit detection on the bus lines among its diagnostic features; with BP at ground instead of its idle level of roughly half the 5 V supply, the difference to BM no longer swings the way the receivers expect. If Bus F is a CAN, a grounded CAN-High stops dominant bits, which onsemi found blocks the bus. Among Volvo's typical triggers for the truck code U008088 is CAN-High grounded. No manufacturer documents U0083 itself. With the battery disconnected, measure the (+) wire to chassis.

Likely causes

(+) wire of Bus F chafed through to body metal

Harness pinched by a trim panel or bracket

Faulty transceiver pulling the (+) line to ground

Symptoms

Several functions on Bus F fail at once
Many lost-communication codes in other modules

Repair estimate

DifficultyHardWorkshop job

Parts and labour€60–800

Time1–5 h

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

Parts involved

bus f wiringcan transceiver

Related codes

U0067 U0080 U0082 U0084

References: nxp.com, onsemi.com, static.nhtsa.gov, law.cornell.edu.