Powertrain, generic · Transmission

P0923 Gear Shift Forward Actuator Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

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

Symptoms

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

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,000
Time0.5–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

gear shift forward actuatorwiring harnesstcm

Related codes

P0920P0921P0922P0927

References: law.cornell.edu, patents.google.com, patents.google.com.