P0944
Hydraulic Pressure Unit Loss of Pressure
- Severity
- High
- Driving
- Drive only to a garage
The hydraulic pressure unit has lost pressure. Without pressure the clutch and selector actuators cannot move, so the transmission cannot change gear and the car will usually not move at all. The most common cause is the simplest: fluid has leaked out.
Possible causes
- CommonExternal hydraulic leak
- CommonLow fluid level
- CommonFailed hydraulic pump
- CommonFailed accumulator
- PossiblePump relay or supply fault, so the pump never runs
- PossibleBlocked filter starving the pump
What you might notice
- Car will not move
- Transmission will not select a gear
- Pump not running, or running without building pressure
- Transmission warning message
- Fluid puddle under the car
What to check, in order
- Look underneath for a leak and check the fluid level. This finds the cause most of the time and costs nothing.
- Listen for the pump when the ignition is switched on. Silence points at the relay, the fuse or the pump itself.
- Check the pump relay and fuse.
- Watch the pressure reading while the pump runs - a pump that runs without building pressure is worn or starved.
- Do not keep switching the ignition on and off to try to build pressure. If the pump is running dry it will destroy itself.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Transmission and control modules
P0900P0901P0902P0903P0904P0905P0906P0907P0908P0909P0910P0911P0912P0913P0914P0915P0916P0917P0918P0919P0920P0921P0922P0923P0924P0925P0926P0927P0928P0929P0930P0931P0932P0933P0934P0935P0936P0937P0938P0939P0940P0941P0942P0943P0944P0945P0946P0947P0948P0949P0950P0951P0952P0953P0954P0955P0956P0957P0958P0959P0960P0961P0962P0963P0964P0965P0966P0967P0968P0969P0970P0971P0972P0973P0974P0975P0976P0977P0978P0979P0980P0981P0982P0983P0984P0985P0986P0987P0988P0989P0990P0991P0992P0993P0994P0995P0996P0997P0998P0999