Powertrain, generic · Transmission

P094B Hydraulic Pump Stuck On

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The hydraulic pump keeps running although the module has switched it off, or it never reaches its cut-out point. Causes are a welded relay or shorted driver, or a pump that cannot reach cut-out pressure because of leakage. No manufacturer documents this exact code publicly. In the pump and accumulator unit of an automated gearbox, described in a ZF patent, the pump should rest once the accumulator is charged. Toyota links a constantly buzzing pump on the MR2 sequential gearbox to fluid loss at the hydraulic power unit, reported under P0942. CARB requires functional checks on outputs. P094C is the opposite fault, P0946 the relay plausibility fault, P0943 the too-short cycle. Battery drain and pump wear follow.

Likely causes

Pump relay contacts welded closed
Leakage or lost accumulator charge keeps pressure below cut-out
Shorted driver stage or supply wire shorted to battery voltage

Symptoms

  • Pump audible after the vehicle is switched off
  • Discharged battery
  • Warning light on

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€30–1,500
Time0.5–4 h

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

Parts involved

hydraulic pumphydraulic pump relaytcm

Related codes

P094CP0946P0943P094A

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