Powertrain, generic (extended)

P28DE Clutch B Pressure Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P28DE means the clutch B pressure sensor delivers a voltage above anything a working sensor would show, even at full clutch pressure. Typical causes are a signal line touching a supply or battery feed, a broken sensor ground, or a signal line open at the sensor end where the input uses a pull-up resistor. No manufacturer documents P28DE publicly. In the actuator layout of a Getrag patent the pressure at each clutch is set by the speed of its own pump motor and checked by a pressure sensor, so a falsely high value would lead the controller to under-apply the clutch; an Audi patent shows the same one-sensor-per-clutch idea. Out-of-range checks on this kind of input are a CARB requirement. P28DD is the low fault and P28CF the clutch A version. The module usually disables clutch B.

Likely causes

Signal wire shorted to the sensor supply or to battery voltage
Sensor ground open or high resistance at the connector
Pressure sensor failed with output stuck high

Symptoms

  • Transmission warning or check engine light on
  • Emergency mode with limited gears
  • Slipping or weak pull when clutch B is in use

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,800
Time0.5–5 h

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

Parts involved

clutch pressure sensor bwiring harnesstcm

Related codes

P28DCP28DDP28DFP28CF

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