P09A4Gate Select Position Circuit B Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Set when the gate select signal on circuit B stays below its lowest valid value for longer than a calibrated time. Likely causes are a signal line shorted to ground, a lost sensor supply or an internal sensor short; with potentiometer sensors like the select position sensor in an Isuzu patent, an open signal wire often reads low too. No manufacturer documents this code publicly, nor whether B is a second track or another sensor. CARB requires out-of-range checks on such inputs. P09A5 is the opposite fault, P09A2 the general circuit fault, P0906 and P09A8 the low faults of circuits A and C. If A and B are both low, look for a shared supply or ground.
- What you may notice
- Check engine or transmission warning light on
- Gear changes blocked or limited to a few gears
- Transmission warning message in the instrument cluster
- Likely causes
- LikelySignal wire of circuit B chafed through and shorted to ground
- PossibleSensor reference supply interrupted or shorted
- PossibleInternal short or broken wiper in the select sensor
- RareFaulty input 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: €80 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.