What Does P0912 Mean?
The TCM has detected that the gate select actuator circuit voltage is below the expected operating range. This low-side fault indicates a short to ground in the actuator circuit wiring, a failed actuator motor with an internal short, or a grounded control wire. The gate select actuator controls the left/right motion for selecting gear gates in automated manual transmissions.
Safety Warning
A low circuit fault prevents proper gate selection, potentially trapping the transmission in one gate or preventing engagement altogether. Do not drive; tow the vehicle.
Common Causes
35%
Short to ground in gate select actuator wiring harness
30%
Gate select actuator motor internal short to case ground
20%
TCM actuator driver circuit failure (output shorted low)
15%
Water intrusion in actuator connector causing conductive path to ground
Diagnostic Steps
1
Step 1: Disconnect the gate select actuator and measure insulation resistance from each motor pin to the actuator case — should be greater than 10M ohms; low readings indicate internal short to ground.
2
Step 2: With the actuator disconnected, measure resistance from each harness wire to chassis ground at the TCM connector — should read OL; any reading indicates a short to ground in the harness.
3
Step 3: Inspect the actuator connector and harness for moisture, corrosion, or physical damage that could create a ground path.
4
Step 4: Measure the actuator motor winding resistance — should be within manufacturer specification (2-15 ohms); significantly low resistance indicates shorted windings.
5
Step 5: If wiring and actuator check good, test the TCM output driver by measuring voltage at the TCM connector pins while commanding the actuator — a stuck-low output indicates TCM failure.
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
The TCM has detected that the gate select actuator circuit voltage is below the expected operating range. This low-side fault indicates a short to ground in the actuator circuit wiring, a failed actuator motor with an internal short, or a grounded control wire. The gate select actuator controls the ...
The most common cause of P0912 (Gate Select Actuator Circuit Low) is: Short to ground in gate select actuator wiring harness
Typical repair costs for P0912 range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A low circuit fault prevents proper gate selection, potentially trapping the transmission in one gate or preventing engagement altogether. Do not drive; tow the vehicle.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0912 to identify the root cause.
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Quick Info
Category
Powertrain
System
Automated Manual Transmission (Shift Control)
Difficulty
Type
Generic (SAE)
Recommended Tools
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