Powertrain, generic · Transmission

P0906 Gate Select Position Circuit A Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Set when the gate select position signal on circuit A of an automated manual gearbox stays below its lowest valid value for longer than a calibrated time. Common causes are a short to ground on the signal line, a missing sensor supply, or an internal sensor defect; with many sensor designs a broken signal wire also reads low. No manufacturer documents this code publicly. Aisin AI and Isuzu describe select stroke and select position sensors with a defined voltage curve across the gates in their patents, so a value below that curve is clearly out of range; CARB calls for out-of-range checks on such inputs. P0907 is the matching high fault, P09A4 and P09A8 are the low faults of circuits B and C. Without a gate signal the gearbox usually locks gear changes or holds a safe gear.

Likely causes

Signal wire chafed through and shorted to ground
Sensor reference supply interrupted or shorted
Internal defect of the gate select sensor
Faulty input stage in the transmission control module

Symptoms

  • Check engine or transmission warning light on
  • No gear changes possible or gearbox stays in neutral
  • Warning message about the transmission on the dashboard

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 awiring harnesstcm

Related codes

P0904P0905P0907P0908P09A4P09A8

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