P0912: Gate Select Actuator Circuit Low

What does P0912 mean?

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.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

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

Common causes

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

Likelihood is a general estimate across vehicles; your make and model may differ.