Powertrain, generic · Transmission

P0921 Gear Shift Forward Actuator Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Plausibility fault in the drive circuit of the forward shift actuator of an automated manual gearbox. The circuit is neither open nor shorted, but current, voltage or the resulting movement do not fit the command, for example a current that is too high for the requested stroke or a shift position that hardly changes. No manufacturer documents this code publicly. A Hyundai/Kia patent explains that jamming raises the motor load of a shift actuator and must be caught early, and a ZF patent shows double-acting shift cylinders with one solenoid valve per chamber. CARB requires functional checks on such outputs. P0920, P0922 and P0923 are the clear electrical faults, P0925 the reverse direction, P0919 the missed target. Forward shifts become slow or fail.

Likely causes

Sticking shift valve, worn shift motor or stiff shift linkage
Solenoid or motor resistance out of specification
Increased contact resistance in connector or wiring
Insufficient hydraulic pressure on hydraulic units

Symptoms

  • Transmission warning light on
  • Slow, harsh or aborted gear changes in one direction
  • Fallback mode with fewer available gears

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–2,000
Time1–5 h

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

Parts involved

gear shift forward actuatorwiring harnesstcm

Related codes

P0920P0922P0923P0925P0919

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