CAN High Voltage Fault Code U0005
Diagnostic trouble code U0005 indicates that the engine control module (ECM) has detected an abnormally high voltage on the CAN High wire of the high-speed controller area network (CAN) bus, typically operating at 500 kbps. Per SAE J2012, this means the signal on the CAN High line exceeds the maximum allowable threshold (approximately 3.5V to 5.0V, depending on the manufacturer) for a calibrated period, preventing proper differential communication between vehicle modules.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Short to battery voltage (B+) on the CAN High wiring
- Open circuit in the CAN High or CAN Low line
- Short circuit between CAN High and CAN Low
- Faulty internal CAN transceiver in a module connected to the bus
- Damaged, corroded, or loose terminals in CAN bus connectors
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Multiple communication-related faults stored in various modules
- Vehicle may experience drivability issues such as stalling, rough idle, or failure to start
- Intermittent or complete loss of communication with scan tool
4. Step-by-Step Diagnosis
Verify the fault is current and note any other CAN-related codes
Visually inspect CAN bus wiring and connectors for damage, corrosion, or loose pins
Measure voltage on CAN High (pin 6 of DLC) and CAN Low (pin 14) with ignition on; CAN High should be ~2.5V–3.5V, CAN Low ~1.5V–2.5V
Check for shorts to battery voltage or ground on CAN High and CAN Low circuits
Isolate modules by disconnecting them one at a time while monitoring bus voltage to identify the faulty module
5. Frequently Asked Questions
Is it safe to drive?▼
Driving with code U0005 is not recommended as it can cause unpredictable drivability issues and may leave you stranded. The severity is high, so have the vehicle diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs vary widely depending on the root cause. Simple wiring repairs may cost $100–$300, while replacing a faulty module can range from $500 to $1,500 or more, including labor.