P0920Gear Shift Forward Actuator Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Concerns the drive circuit that moves the shift mechanism of an automated manual gearbox in the forward shift direction. Depending on design this is one of two solenoid valves on a double-acting shift cylinder or one rotation direction of an electric shift motor. The code sets when the module finds this output open or electrically faulty, e.g. no current while the driver is on. No manufacturer documents the code publicly. A ZF patent feeds each chamber of a double-acting cylinder through its own 3/2 solenoid valve, an Isuzu patent turns the shift motor forward or reverse by shift direction. CARB requires circuit checks on outputs. P0921 to P0923 are the siblings, P0924 the reverse direction. Gears in this direction can no longer be engaged.
- What you may notice
- Transmission warning light on
- Some gears cannot be selected, the gearbox skips them or stays in neutral
- Vehicle may only move off in a limited set of gears
- Likely causes
- LikelyLoose, corroded or unplugged connector at the shift actuator or valve
- PossibleBroken drive wire between module and actuator
- PossibleOpen solenoid coil or motor winding in the actuator
- RareFaulty driver stage in the transmission control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.