What does it mean?
U2012 is a Network (CAN bus, module communications) fault code. It indicates: Torque Reduction (Engine Condition) Signal Line .
Symptoms
- Harsh, delayed or flaring gear changes
- Traction control lamp and check engine lamp on
- Engine hesitates or cuts power during shifts
- Transmission falls into limp mode and holds a single gear
- Reduced power message on the driver display
- Poor drivability under acceleration
Likely causes
- Break or short in the torque reduction signal line between the engine and transmission control modules
- Corroded or loose connector on that signal circuit
- Engine or transmission module without proper power or ground, so the signal is never sent
- Failed output driver inside the transmitting module
- Wiring damaged after engine or gearbox removal and refitting
- Software mismatch between the modules after a replacement or a partial flash
- Aftermarket tuning device tapped into the signal circuit
How to fix it
- Read codes in both the engine and transmission modules and compare their live data
- Watch the torque reduction request during a road test, or on a lift with the wheels free
- Inspect the connectors and wiring between the two modules for corrosion and damage
- Test the signal circuit for open circuit, short to ground and short to battery
- Check power and ground at both modules with a voltage drop test
- Remove any aftermarket tuning device and retest
- Verify module software levels; replace a module only once the wiring has been proven