P0943
Hydraulic Pressure Unit Cycling Period Too Short
- Severity
- High
- Driving
- Drive only to a garage
The hydraulic pump is cycling too often - it charges the accumulator, and the pressure falls again far sooner than it should. Pressure is escaping somewhere. This is one of the more useful codes in this range because it points almost directly at a leak or a failed accumulator rather than at the pump itself.
Possible causes
- CommonExternal hydraulic leak - pipes, seals or the actuator
- CommonFailed accumulator, unable to store pressure
- CommonInternal leak past a worn valve or seal
- CommonLow fluid level
- PossibleFaulty pressure sensor causing unnecessary pump cycles
- PossibleWorn pump unable to maintain pressure
What you might notice
- Pump running frequently, including with the car standing still
- Slow or failed gear changes
- Transmission warning message
- Fluid leak visible under the car
- Pump noise more noticeable than usual
What to check, in order
- Look underneath for a leak. Frequent pump cycling with a falling fluid level is a leak until proven otherwise.
- Watch the pressure reading after the pump stops. Pressure that falls away quickly with the car stationary confirms it is escaping rather than being used.
- Suspect the accumulator if there is no external leak and the fluid level is correct - a failed accumulator loses its ability to store pressure and the pump has to make up the difference constantly.
- Check the fluid level and condition.
- Do not ignore this. A pump running constantly wears out quickly and overheats the fluid, so a cheap repair becomes an expensive one if left.
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