Fault codeP0921

MODERATE

Gear Shift Foward Actuator Circuit Range/Performance

What this code means

Gear Shift Foward Actuator Circuit Range/Performance.

P0921 is a generic code: it means the same thing on every make. P0921 belongs to family P09xx — Transmission and controls. Its page explains how to read a code and groups all its codes by part.

Type of fault

The signal stays within its electrical limits, but its value is not plausible: it does not match what the control unit expects given the other sensors. The sensor may be drifting with age, but it may also be faithfully measuring a real mechanical problem — a leak, a blockage, an air leak. Replacing the sensor without checking does not always clear the fault.

Automated gearbox actuators

Automated manual gearboxes are manual gearboxes whose clutch and gear changes are operated by actuators, hydraulic or electric. Sensors measure the clutch position and the selector position, and the control unit learns these positions.

What you notice

Jerky starts, a slipping clutch, a gear that will not engage, a gearbox stuck in neutral.

How to check it

Check the hydraulic fluid level if the system uses one, the actuators' connectors and the battery voltage, since these gearboxes are sensitive to it. After any repair or a battery disconnection, a relearn of the positions with a suitable tool is often required.

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →

How to read this code

PPowertrain
0standardised code
9Transmission and controls
21P0921