Powertrain, generic · Transmission

P09A9 Gate Select Position Circuit C High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Logged when the gate select signal on circuit C sits above its highest plausible value for longer than a calibrated time. Usual suspects are a short to the sensor supply or battery voltage, an interrupted sensor ground, or a sensor with an internal fault. No manufacturer publicly documents this code, and the physical meaning of circuit C is not published either. An Aisin AI patent describes the fallback once select feedback is lost: warning, stop request and a limp-home in first gear. CARB requires out-of-range checks on such inputs. P09A8 is the low counterpart, P09A6 the general C fault, P0907 and P09A5 the high faults of A and B. Shifting is usually curtailed.

Likely causes

Signal wire of circuit C shorted to supply or battery voltage
Open or corroded sensor ground
Internal fault of the sensor delivering signal C
Faulty input stage in the transmission control module

Symptoms

  • Check engine or transmission warning light on
  • Limp-home mode, often in a single low gear
  • Gear changes refused while driving

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,500
Time0.5–4 h

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

Parts involved

gate select position sensor cwiring harnesstcm

Related codes

P09A6P09A7P09A8P0907P09A5

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