Powertrain, generic (extended)

P28DC Clutch B Pressure Sensor Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P28DC concerns the sensor that reports the hydraulic pressure acting on clutch B of a dual-clutch or hybrid transmission. The code points to a broken connection: the module receives no usable signal at all, as happens when a signal, supply or ground wire is open or the connector has come off. No manufacturer documents P28DC publicly. A Getrag patent shows why the reading matters: each clutch has its own actuator pump with a dedicated electric drive, and the measured pressure closes the loop over motor speed; an Audi patent likewise gives every clutch its own pressure sensor. CARB requires circuit checks on such inputs. Which clutch carries the letter B is up to the maker. Without the signal the module runs clutch B on a fallback or takes it out of use.

Likely causes

Connector at the sensor or transmission plug loose, unplugged or with a pushed-back pin
Signal, supply or ground wire of the sensor broken
Pressure sensor internally open
Sensor input in the transmission control module faulty

Symptoms

  • Transmission warning or check engine light on
  • Gears served by clutch B blocked, transmission in emergency mode
  • Jerky launch or harsh shifts

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

P28DDP28DEP28DFP28CDP28DA

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