Gate Select Position Circuit A
What it means
P0904 flags a fault in the "A" gate select position circuit on an automated-manual or electronically shifted transmission. The gate select sensor reports which shift gate the selector is in, and if that signal is invalid the transmission can't reliably choose gears. The engine starts and runs, but you may see difficulty engaging gears, a wrong-gear display, or limp mode. Wiring, the sensor, and the selector mechanism are the usual suspects.
Can I keep driving? The engine starts, but the car may struggle to select gears or drop into limp mode — get it checked before you're left unable to shift.
Common symptoms
What you'll notice
- Check-engine light on
- Difficulty selecting or engaging gears
- Wrong gear shown on the instrument cluster
- Delayed or erratic response when shifting
- Transmission may enter limp/limited mode
Common causes
Most likely first
- Faulty gate select position sensorLikely
- Wiring or connector fault in the gate select circuitCommon
- Loose or corroded connector at the sensorCommon
- Mechanical problem in the shift/selector mechanismLess often
- Faulty shift control module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and compare the reported gate position with the actual selector position.
- Inspect the gate select sensor connector and wiring for damage, corrosion, or loose pins.
- Measure the sensor's signal across its range against spec.
- Check the selector mechanism for binding or mechanical wear.
- Replace the sensor if it reads out of range, repair wiring as needed, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0904?+
Can I just clear P0904?+
Related codes
Often seen with P0904
Read & clear P0904 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.