P0923: Gear Shift Forward Actuator Circuit High

Set when the drive circuit of the forward shift actuator of an automated manual gearbox shows a voltage that is too high for the current switching state. Typical reasons are a valve or motor line shorted to battery voltage, or a driver stage in the module that no longer switches off; depending on circuit design an open load can also read high. No manufacturer documents this code publicly. A ZF patent describes double-acting shift cylinders whose chambers each have a 3/2 solenoid valve, and an Isuzu patent drives a shift motor forward or reverse by shift direction. CARB requires circuit checks on outputs. P0922 is the opposite low fault, P0920 the open circuit, P0927 the reverse direction. An actuator that stays energised can hold or force a gear, so shifting is usually locked.

Medium severity. Can I keep driving?Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

Symptoms

Transmission warning light on
Gearbox locks in one gear or refuses to shift
Possible grinding when a gear is pushed unintentionally

Most likely causes

Drive wire shorted to battery voltage
Driver stage in the control module stuck on
Open coil or winding read as high on some circuit designs

What to check, in order

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

Check the fluid level and condition according to the manufacturer
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Check the transmission connector
Read the data with a transmission-compatible scanner
Measure the solenoid valve circuit
Leave opening the transmission to a specialized repair shop

Good to know

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

What each character of P0923 means

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

Frequently asked questions

Can I keep driving with code P0923?

Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

What causes code P0923?

The most common causes are: drive wire shorted to battery voltage; driver stage in the control module stuck on; open coil or winding read as high on some circuit designs.

Related codes

Sources

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.