U0002: High Speed CAN Communication Bus Performance
The high-speed CAN bus is functional but performance is degraded — frame errors, bit errors or excessive bus load have been detected. Communication may be intermittent rather than completely lost, leading to sporadic warning lamps.
What U0002 means
U0002 is a generic OBD-II network code in the bus & wiring group. In plain English: the signal is within electrical limits but doesn’t make sense compared with other readings, so the part or system isn’t performing as expected.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
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Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
- 01Corrosion or poor contact in CAN connectorsMost likely
- 02Electromagnetic interference (aftermarket electronics)Possible
- 03One module sending malformed framesPossible
Can I drive with U0002?
Usually yes, for a short time.
The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
Why we rate it moderate
- Turns on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose U0002
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just U0002. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Fix other faults first
If other codes are stored, start with power-supply, sensor-circuit and communication codes. They can cause this code as a side effect.
- 3
Check module power, ground and the data bus
Confirm the module named in the code has battery voltage, ignition feed and a good ground. With the battery disconnected, a healthy CAN bus usually measures about 60 ohms between CAN-High and CAN-Low at the OBD port. Inspect connectors for corrosion and pushed-out pins.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Corrosion or poor contact in CAN connectors; electromagnetic interference (aftermarket electronics); one module sending malformed frames. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
U0002 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Hard
- Good DIY job?
- Usually a shop job
Involved testing or major parts. Most owners use a shop.
Parts and systems involved
- CAN bus wiring
- Control module
U0002 FAQ
What does U0002 mean?
U0002 means “High Speed CAN Communication Bus Performance”. The high-speed CAN bus is functional but performance is degraded — frame errors, bit errors or excessive bus load have been detected. Communication may be intermittent rather than completely lost, leading to sporadic warning lamps.
Is U0002 serious? Can I keep driving?
We rate U0002 as moderate severity. Usually yes, for a short time. The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
What causes U0002?
The most common causes, from most to least likely: Corrosion or poor contact in CAN connectors; Electromagnetic interference (aftermarket electronics); One module sending malformed frames. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix U0002?
Typical labor is about $125–$750 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix U0002 myself?
DIY difficulty is hard. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will U0002 clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.