P0904Gate Select Position Circuit A
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Circuit A of the gate select position sensor tells the control module of an automated manual gearbox where the shift mechanism stands in the select direction, i.e. which gate (for example 1-2, 3-4, 5-6 or reverse) is lined up. This generic circuit code sets when the module sees an electrical fault on that signal that is not covered by the more specific low, high or intermittent variants. No manufacturer documents the code publicly. Aisin AI and Isuzu patents describe such select stroke or select position sensors working next to an electric or hydraulic select actuator, and CARB requires circuit checks on transmission inputs of this kind. P0905 to P0908 are the siblings, P09A2 and P09A6 the same signal on circuits B and C. Without a valid gate signal the gearbox usually stops shifting or holds one gear.
- What you may notice
- Check engine or transmission warning light on
- Gearbox stops shifting or stays in one gear
- Neutral indicator flashes or vehicle will not pull away
- Likely causes
- LikelyLoose, corroded or water-damaged connector at the gate select sensor or actuator unit
- PossibleChafed or broken sensor wiring near the gearbox
- PossibleFaulty gate select position sensor (often integrated in the shift and select actuator)
- RareFaulty sensor input or reference supply 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 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.