Powertrain, generic · Transmission

P0943 Hydraulic Pressure Unit Cycling Period Too Short

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

In a hydraulic pressure unit the pump charges an accumulator up to a cut-out pressure and switches off until pressure falls to the cut-in point. By J2012 wording this code means the pump switches on again too soon, so the interval between charging cycles is shorter than expected. Typical reasons are internal leakage across valves or seals, or an accumulator that has lost its gas precharge and stores too little oil. Audi patents describe such accumulator and leakage checks based on charging switch-over times and pressure decay. No manufacturer documents this exact meaning publicly; Ferrari uses P0943 on its DCT for a system pressure command signal that is too high. CARB requires functional checks of transmission outputs. P0942 is the general fault, P0944 the loss of pressure.

Likely causes

Accumulator has lost its gas precharge
Internal leakage at valves, seals or actuator cylinders
Faulty pressure switch or pressure sensor giving wrong cut-in point
Low or aerated hydraulic fluid

Symptoms

  • Pump can be heard switching on unusually often
  • Warning light on
  • Slower or harsher gear changes

Repair estimate

DifficultyHardWorkshop job
Parts and labour€200–2,500
Time1.5–6 h

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

Parts involved

hydraulic pressure unittcm

Related codes

P0942P0944P094BP0868

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