This code indicates that Vehicle Communication Bus B (typically a Controller Area Network bus linking multiple control modules) has detected a short-circuit condition. The short may be between the two communication lines (CAN high and CAN low), or between either line and battery voltage or ground. This prevents modules from exchanging data and often causes widespread communication failures across the network.
The Bus B twisted-pair wiring has rubbed against a metal bracket, sharp edge, or heat source, wearing through the insulation and causing the CAN high and low circuits to short together, or either wire to short to ground or battery voltage.
Moisture has entered a module connector, junction block, or pass-through point, creating a conductive path between the bus terminals or to the vehicle frame, effectively shorting the communication lines.
Any module attached to Bus B (such as the ABS module, airbag control module, or body control module) may have an internal failure causing its communication transceiver to pull the bus lines to ground or power continuously.
An improperly installed remote start system, alarm module, or diagnostic tool left connected has tapped into the Bus B wiring, introducing a short circuit or excessive current draw that disrupts bus voltage levels.
Rarely, the PCM/ECM internal CAN transceiver may fail and create a short across the bus terminals; however, this is uncommon and should only be considered after all wiring and other modules have been eliminated as causes.
Almost certainly not. Despite some repair information suggesting PCM replacement for U0045, the root cause is almost always wiring damage, connector issues, or another module on the bus. The PCM should be the last component considered, and only replaced if proven faulty through isolation testing.
It is not recommended. A shorted communication bus can disable critical safety systems including anti-lock brakes, airbags, and electronic stability control. The engine may also stall without warning or fail to restart.
Because Bus B is a shared network connecting multiple modules, a short affects the entire network. When modules cannot communicate with each other, they typically illuminate warning lights for their respective systems and store additional codes indicating which modules cannot be reached.
Clearing the code will not repair a physical short. If the short is present, the code will immediately reset or the bus will remain inoperative. Clearing is only useful after the repair has been made to verify the fix.