Powertrain, generic · Transmission

P0821 Gear Lever X Position Sensor 1 Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Gear lever X and Y position sensors detect a selector's position in two directions: on an H-gate shift and select direction (a LuK patent uses two sensors about 90° apart), on a shift-by-wire lever its two axes. P0820 covers the whole X-Y circuit, P0821–P0824 and P082A–P082F sensor 1, P089A–P08A3 a redundant sensor 2. P0821 is the general circuit fault of X sensor 1 – an open or invalid signal – for modules that do not report low and high separately. No manufacturer document available to us uses it; GM reports the same axis in finer steps as P082A, P082B and P082C. A GM patent describes checking each sensor's x value separately: an invalid value makes that sensor unusable, and with a redundant sensor 2 the car can usually go on.

Likely causes

X position sensor in the selector assembly faulty
Signal wire or connector open or corroded
Liquid or dirt in the center console
Control module

Symptoms

  • Transmission warning in the cluster
  • Ranges partly not selectable
  • With both sensors failed the vehicle stays in P or N

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–800
Time0.5–2.5 h

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

Parts involved

gear lever position sensorelectronic range selectorsensor wiringtransmission control module

Related codes

P0820P0822P082AP082BP082C

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