P0942
Hydraulic Pressure Unit
- Severity
- High
- Driving
- Drive only to a garage
A general fault with the hydraulic pressure unit - the pump, accumulator and valve assembly that provides the pressure the clutch and selector actuators run on. Nothing in this transmission moves without it, so a fault here usually stops the car changing gear at all.
Possible causes
- CommonLow hydraulic fluid level or a leak
- CommonFailed accumulator no longer holding pressure
- CommonWorn or failing hydraulic pump
- CommonFailed pump relay or supply fault
- PossibleBlocked filter in the hydraulic circuit
- PossibleFaulty pressure sensor misreporting the unit's state
What you might notice
- Transmission will not change gear
- Car will not move
- Pump running constantly or not running at all
- Transmission warning message
- Fluid leak near the transmission
What to check, in order
- Check the hydraulic fluid level and look for leaks first. It is visible from underneath and it is the most common cause.
- Listen for the pump. Silence points at the relay or supply; constant running points at a leak or a failed accumulator.
- Watch the pressure reading through a pump cycle on the live data screen.
- Check the pump relay and its fuse.
- Read all codes - the more specific pressure unit and pump codes narrow this down considerably.
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