U0063

Vehicle Communication Bus D (-) shorted to Bus D (+)

Communication network (CAN bus) Generic OBD-II High

What it means

U0063 means the two wires of vehicle communication Bus D — CAN-low (-) and CAN-high (+) — are shorted together, which can collapse the entire bus so its modules stop communicating. This is one of the more serious network faults: multiple modules can drop offline at once, and if the powertrain bus is affected the car may go into limp mode, stall, or fail to start. It almost always traces to a pinched or damaged harness or a failed module.

High

Can I keep driving? Often no — a short between the two bus wires can collapse the whole network, taking multiple modules offline at once; if the powertrain bus is affected expect limp mode, stalling, or a no-start. Treat as urgent.

Common symptoms

What you'll notice

Many warning lights on at once with multiple modules reporting lost communication
Widespread feature loss — the affected bus can go completely dead
Reduced power, limp mode, stalling, or a no-start if the powertrain bus is involved
Gauges and displays blank or frozen

Common causes

Most likely first

CAN-low (-) and CAN-high (+) wires shorted together (chafed, pinched, or crushed harness)Likely
Damaged or water-intruded connector bridging the two bus wiresCommon
A failed module internally shorting the two bus linesCommon
Repair or accident damage that pinched the bus harnessLess often
Rodent damage to the wiringLess often

How to diagnose & fix

Work through it in order

Scan all modules; a bus-wide short usually shows many modules reporting communication loss at once.
Measure resistance across CAN-high/low — a short between them reads far below the normal ~60 ohms.
Inspect the Bus D harness for pinched, chafed, or crushed sections and damaged connectors.
Disconnect modules one at a time to see if the short clears, isolating a failed module.
Repair the shorted wiring or replace the faulty module, then confirm normal bus resistance and re-test.

FAQ

Quick answers

Is it safe to drive with U0063?+

Often not. A short between the bus wires can bring the whole network down, and if the engine or transmission modules are on it the car may stall or fail to start. Have it diagnosed before driving.

Can I just clear U0063?+

No — this is a hard wiring short, so the code returns instantly. The bus can't work correctly until the short is found and repaired.

Related codes

Often seen with U0063

U0058Vehicle Communication Bus D (+) Low U0059Vehicle Communication Bus D (+) High U0060Vehicle Communication Bus D (-) Open U0061Vehicle Communication Bus D (-) Low

Read & clear U0063 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX