P0912: Gate Select Actuator Circuit Low

Set when the drive circuit of the gate select actuator of an automated manual gearbox shows a voltage that is too low for the current switching state, which usually means a short to ground on a motor or control line, or an internal short in the actuator. Many controllers then switch the affected output off to protect the driver stage. No manufacturer documents this code publicly. Isuzu and Hyundai/Kia describe in their patents select and shift actuators built as electric motors and driven by the transmission controller, which is the hardware this circuit check covers; CARB requires circuit monitoring of such outputs. P0913 is the matching high fault, P0910 an open circuit and P0911 a plausibility fault. With the select actuator disabled, the gearbox can no longer change gates.

Symptoms

• Check engine or transmission warning light on
• No gate change possible, gearbox stays in current gear or neutral
• Vehicle may not pull away

Most likely causes

• Actuator wire chafed through and shorted to ground
• Internal short in the select motor, e.g. from brush debris
• Faulty driver stage in the transmission control module

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery, connectors, and wiring
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Read the live data with a scanner
4. Follow the manufacturer's service manual

Good to know

• Repair difficulty: hard
• It can trigger limp mode.
• It affects emissions.

What each character of P0912 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 9: Transmission
• 12: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0912?

If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.

What causes code P0912?

The most common causes are: actuator wire chafed through and shorted to ground; internal short in the select motor, e.g. from brush debris; faulty driver stage in the transmission control module.

Related codes

• P0909Gate Select Control Error
• P0910Gate Select Actuator Circuit/Open
• P0911Gate Select Actuator Circuit Range/Performance
• P0913Gate Select Actuator Circuit High

Sources

• law.cornell.edu: 13 CCR 1968.2
• patents.google.com: en
• patents.google.com: en

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.