Powertrain, generic · Transmission

P0944 Hydraulic Pressure Unit Loss of Pressure

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

The pump runs but the expected hydraulic pressure does not build or collapses. Stellantis names it Loss of Hydraulic Pump Prime: a 2023 STAR case lists it with P0868 and a slow engagement after the vehicle has stood, both set as the only transmission codes with the MIL on, and the fix was a new transmission; an FCA defect file from 2015 also shows it beside line pressure low. Mercedes uses P0944 on the 722.9 automatic with electric auxiliary oil pump for stop-start, as internal fault of that pump; stop-start stops working, and a leaking check valve between converter housing and pump is one cause. Ferrari reads it on its DCT as no system pressure signal with pressure loss. P0943 covers short cycles, P0868 low fluid pressure.

Likely causes

Pump loses prime (air drawn in through filter, seal or strainer pipe)
Blocked oil strainer or suction tube
Worn or failed pump (mechanical or electric)
Leaking check valve or internal leak in the valve body

Symptoms

  • Check engine or transmission warning light on
  • Slow engagement after the vehicle has been parked
  • Auto stop-start not available or engine restarts at once
  • Slipping, no drive or limp mode

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–6,000
Time1–12 h

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

Parts involved

hydraulic pressure unittcm

Related codes

P0942P0943P094CP0868

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.