Code U0002 on the 2021 Acura TLX indicates that the CAN Bus A circuit is reading high - meaning the voltage on the CAN lines is above normal operating range. This condition prevents proper data transmission between modules on the high-speed CAN network.
CAN Bus Voltage Specifications
High-speed CAN uses differential signaling with CAN-High (CAN-H) and CAN-Low (CAN-L) lines. During transmission, CAN-H goes to approximately 3.5V while CAN-L drops to approximately 1.5V. A 'circuit high' condition means these voltages are above normal, typically indicating a short to a higher voltage source.
Communication Impact
With U0002 present, modules cannot properly decode CAN messages because the voltage levels are incorrect. Multiple communication fault codes appear across various modules. The vehicle may exhibit reduced functionality or refuse to start depending on which modules are most affected.
Diagnostic Focus
Look for shorts to power in the CAN wiring harness. A wire rubbing against a power source, damaged insulation touching battery voltage, or a faulty module outputting incorrect voltage can all cause this condition. Check areas where CAN wiring passes near power distribution points or fuse boxes.
Repair Strategy
Measure CAN-H and CAN-L voltages with a multimeter to confirm the high condition. Trace wiring to find the short source. Disconnect modules systematically while monitoring voltage to identify if a specific module is causing the high condition. Repair wiring damage or replace the offending module.