P0721

P0721

Speed Sensor, Output Drive

NOTE: The ratio of transmission output speed to vehicle reference speed is monitored.

Diagnostic conditions:
- Average wheel speed, rear axle > 100 rpm
- Selector lever position D or M
- Gear engagement has been completed
- Turbine speed > 1000 rpm
- Faults "U0129 No communication with PSM control unit", "U0418 PSM control unit fault, "P0706 Multi-functional switch" or "P0716 Turbine speed sensor' not detected

Possible fault causes:
- Short circuit to B+/ground/between lines or open circuit
- Signal line insulation faulty
- Speed sensor, output drive faulty
- Control module faulty
- Transmission faulty

Fault reaction:
- From fault detection to fault confirmation and entry:
- The current gear is held.
- The torque converter lockup clutch is opened and held open.
- After fault confirmation and entry:
- A warning is displayed in the instrument cluster.
- The transmission is shifted into mechanical limp home mode, i.e.:
- The pressure adjuster and solenoid valves are switched off.
- This opens the torque converter lockup clutch and 4th gear is firmly selected.
- The gear display shows 4th gear.