P0906 code meaning
Gate Select Position Circuit A Low
Powertrain system Generic code P09xx codes Check engine light
What P0906 means
Set when the gate select position signal on circuit A of an automated manual gearbox stays below its lowest valid value for longer than a calibrated time. Common causes are a short to ground on the signal line, a missing sensor supply, or an internal sensor defect; with many sensor designs a broken signal wire also reads low. No manufacturer documents this code publicly. Aisin AI and Isuzu describe select stroke and select position sensors with a defined voltage curve across the gates in their patents, so a value below that curve is clearly out of range; CARB calls for out-of-range checks on such inputs. P0907 is the matching high fault, P09A4 and P09A8 are the low faults of circuits B and C. Without a gate signal the gearbox usually locks gear changes or holds a safe gear.
P0906 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0906
- Check engine or transmission warning light on
- No gear changes possible or gearbox stays in neutral
- Warning message about the transmission on the dashboard
Common causes of P0906
- Most likelySignal wire chafed through and shorted to ground
- PossibleSensor reference supply interrupted or shorted
- PossibleInternal defect of the gate select sensor
- Less likelyFaulty input stage in the transmission control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Gate select position sensor aWiring harnessTCM
What each part of P0906 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 9 | Area: transmission. |
| 06 | The exact fault in that area. |
What to do next
- Note P0906 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0906
What does P0906 mean?
P0906 means "Gate Select Position Circuit A Low". Set when the gate select position signal on circuit A of an automated manual gearbox stays below its lowest valid value for longer than a calibrated time. It is a generic code, so it means the same on every make.
Is it safe to drive with P0906?
Drive gently and only to a workshop. With P0906 the car can go into limp mode (reduced power) to protect itself.
Will P0906 fail an emissions test?
Yes, it can. P0906 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0906 to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P0906 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.