CAN Bus A Short Circuit Fault
Diagnostic trouble code U0036 indicates that the vehicle's Communication Bus A has been detected shorted to itself. According to SAE J2012, this is a network communication code (U0000-U1000). Bus A typically refers to the main Controller Area Network (CAN) bus, which connects critical modules such as the ECM, TCM, ABS, and other controllers. A bus shorted to itself creates a loop or termination fault, preventing data messages from being transmitted correctly between modules.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty or incorrect value bus termination resistors
- Internal short circuit in the bus control module
- Damaged CAN bus wiring (CAN-H and CAN-L wires shorted together)
- Corroded network connector or damaged pins causing a short
- Failed communication bus control module (gateway module)
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Multiple modules not communicating, causing drivability issues or loss of functions
4. Step-by-Step Diagnosis
Scan all modules for communication faults and verify U0036 is present
Inspect CAN bus wiring for damage, corrosion, or shorts between CAN-H and CAN-L
Check termination resistors at the ends of the CAN bus for correct resistance (typically 60 ohms total)
Test the gateway module and other bus control modules for internal shorts
Repair or replace any faulty wiring, connectors, or modules as needed
5. Frequently Asked Questions
Is it safe to drive?▼
No, driving with this code is not recommended as it can cause unpredictable behavior or loss of critical systems. Have the vehicle diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs vary widely depending on the root cause, typically ranging from $100 for a simple wiring repair to $800 or more if a module replacement is needed.