U0008 — High Speed CAN Communication Bus (-) High

What does OBD2 code U0008 mean?

OBD2 code U0008 flags a problem with the vehicle network (CAN bus) communication (high speed CAN communication bus (-) high). Short, gentle driving to a shop is usually possible. Common culprits: water ingress in harness junctions, aftermarket equipment interfering with the bus, corroded connectors, especially in wet areas.

How much does it cost to fix U0008?

Repair CAN wiring or connectors — $100–$400; Replace the faulty control module — $300–$1,500; Remove interfering aftermarket device — $0–$150. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

How do I diagnose U0008 myself?

Start with a scan: confirm U0008, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the vehicle network (CAN bus) communication, and verify the suspect component against live data before buying parts.

Will U0008 clear itself?

Sometimes U0008 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What are the symptoms of U0008?

Drivers most often notice: modules intermittently not communicating with the scanner, multiple warning lights on at once, random, hard-to-reproduce electrical glitches, intermittent loss of functions (gauges, windows, steering assist).

What does U0008 mean?

Seeing U0008 on your scanner? The control unit has caught the vehicle network (CAN bus) communication operating outside its calibrated window. The formal description is “High Speed CAN Communication Bus (-) High”, and the code is grouped under vehicle network faults.

The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores U0008 and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.

What causes U0008?

• corroded connectors, especially in wet areas
• damaged CAN bus wiring or short to power/ground
• poor grounds or low battery voltage
• water ingress in harness junctions
• aftermarket equipment interfering with the bus
• a faulty module pulling the bus down

Common symptoms of U0008

• modules intermittently not communicating with the scanner
• multiple warning lights on at once
• random, hard-to-reproduce electrical glitches
• intermittent loss of functions (gauges, windows, steering assist)
• no-start or intermittent starting in some cases

How to diagnose U0008

1. Connect an OBD2 scanner, confirm U0008 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
3. Visually inspect the wiring harness and connectors related to the vehicle network (CAN bus) communication for damage, corrosion, chafing or poor contact.
4. Measure resistance between CAN-High and CAN-Low at the OBD port with power off — about 60 Ω is healthy.
5. Scan all modules: the one that does not respond is either the culprit or downstream of the break.
6. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U0008 does not return.

How to fix U0008

Start with the cheapest and most common causes before replacing expensive parts:

• Repair CAN wiring or connectors — $100–$400
• Replace the faulty control module — $300–$1,500
• Remove interfering aftermarket device — $0–$150

How much does it cost to fix U0008?

Repair cost depends on which component actually failed. Typical scenarios for U0008 (parts and labor, USD, independent shop rates):

• Repair CAN wiring or connectors: $100–$400
• Replace the faulty control module: $300–$1,500
• Remove interfering aftermarket device: $0–$150

Overall, fixing U0008 usually costs between $0 and $1,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with U0008?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

Related OBD2 codes

• U0001: High Speed CAN Communication Bus
• U0002: High Speed CAN Communication Bus Performance
• U0003: High Speed CAN Communication Bus (+) Open
• U0004: High Speed CAN Communication Bus (+) Low
• U0005: High Speed CAN Communication Bus (+) High
• U0006: High Speed CAN Communication Bus (-) Open