Powertrain, generic (extended)

P28F3 Engine Disconnect Clutch Pressure Sensor Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P28F3 is stored when the voltage of the disconnect clutch pressure sensor drops below the smallest value a healthy part can output, a level that stands for an electrical fault, not for an open clutch. The usual suspects are a signal wire chafed against ground, a sensor reference supply that is missing or dragged down by another shorted sensor on the same feed, or a failed sensor. No manufacturer documents P28F3 with a threshold in public. Ford uses a separate pressure sensor at this clutch in its 10R80 hybrid gearbox, and a Hyundai patent shows the same single-sensor layout for the engine clutch. CARB requires out-of-range checks on such inputs. P28F4 is the high fault and P28F1 the unspecified circuit fault. The controller usually keeps the clutch open or runs it without feedback.

Likely causes

Signal wire shorted to ground through chafed insulation
Sensor reference supply missing or pulled low by another shorted sensor
Pressure sensor failed with output stuck low

Symptoms

  • Hybrid or transmission warning light
  • Engine coupling blocked, car runs electrically or in limp mode
  • Harsh engagement if the clutch is still used

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time0.5–5 h

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

Parts involved

engine disconnect clutch pressure sensorwiring harness

Related codes

P28F1P28F2P28F4P28F5

References: law.cornell.edu, static.nhtsa.gov, patents.google.com.