What Does U0008 Mean?
The negative (CAN Low) wire of the high-speed Controller Area Network bus is reading an abnormally high voltage. This indicates a short to voltage or a circuit fault that prevents proper differential signaling between modules.
Safety Warning
Vehicle may experience complete communication failure between safety-critical modules including ABS, airbag systems, and engine control. May result in no-start condition or multiple system failures while driving.
Common Causes
35%
CAN Low wire shorted to 12V power source due to damaged wiring harness or pinched wire
30%
Faulty module with internal short pulling CAN Low line high
20%
Damaged or corroded connector pins causing cross-circuit contamination
10%
Aftermarket accessory or trailer wiring improperly tapped into CAN network
5%
Failed terminating resistor causing voltage imbalance on network
Diagnostic Steps
1
Step 1: Using a digital multimeter, measure voltage on CAN Low wire at multiple points with key on, engine off (should be approximately 2.5V nominal, 1.5-2.0V recessive)
2
Step 2: Disconnect modules one at a time to isolate which module or circuit segment is causing the high voltage condition
3
Step 3: Inspect all CAN bus wiring harnesses for signs of damage, pinching, or contact with hot engine components
4
Step 4: Check for aftermarket installations that may have tapped into the CAN network improperly
5
Step 5: Measure resistance between CAN High and CAN Low at network endpoints with all modules disconnected (should be 60 ohms with terminating resistors intact)
Estimated Repair Cost
$150 - $1,500
Parts + labor, varies by vehicle and location
The negative (CAN Low) wire of the high-speed Controller Area Network bus is reading an abnormally high voltage. This indicates a short to voltage or a circuit fault that prevents proper differential signaling between modules.
The most common cause of U0008 (High Speed CAN Communication Bus (-) High) is: CAN Low wire shorted to 12V power source due to damaged wiring harness or pinched wire
Typical repair costs for U0008 range from $150 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may experience complete communication failure between safety-critical modules including ABS, airbag systems, and engine control. May result in no-start condition or multiple system failures while driving.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0008 to identify the root cause.
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Quick Info
Category
Network
System
Network Communications
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
