Powertrain, generic · Transmission

P0942 Hydraulic Pressure Unit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

General fault of the unit that generates and stores hydraulic pressure for an automated gearbox or its auxiliary oil supply: motor-driven pump, accumulator and pressure control. Toyota sets P0942 on the 2001 to 2005 MR2 Spyder sequential gearbox together with the SMT warning light and a buzzing pump, or with gears that can no longer be changed; fluid seeping from the reservoir cap or the seal of the hydraulic power unit is a known cause, fixed with new seal rings. Ferrari reads P0942 on its DCT differently, as system pressure command signal too low. CARB requires functional checks of transmission outputs. P0943 and P0944 are the cycling and pressure-loss faults, P0945 to P0948 the pump control circuit.

Likely causes

Fluid loss at the reservoir cap or hydraulic power unit seals
Worn pump motor or faulty pump relay
Damaged wiring, connectors or power supply of the pump
Transmission control module fault

Symptoms

  • Transmission or gearbox warning light on
  • Pump buzzing or running for long periods
  • Gears cannot be changed or shifts are delayed
  • Auto stop-start disabled or engine restarts immediately

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–2,500
Time1–6 h

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

Parts involved

hydraulic pressure unittcm

Related codes

P0943P0944P0945P0946P094C

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.