What P0942 means
General fault of the unit that generates and stores hydraulic pressure for an automated transmission or its auxiliary oil supply: motor-driven pump, accumulator and pressure control.
How the engine computer detects it
Toyota sets P0942 on the 2001 to 2005 MR2 Spyder sequential transmission together with the SMT warning light and a buzzing pump, or with gears that can no longer be changed; fluid seeping from the reservoir cap or the seal of the hydraulic power unit is a known cause, fixed with new seal rings. Ferrari reads P0942 on its DCT differently, as system pressure command signal too low. CARB requires functional checks of transmission outputs. P0943 and P0944 are the cycling and pressure-loss faults, P0945 to P0948 the pump control circuit.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Transmission or transmission warning light on
- Pump buzzing or running for long periods
- Gears cannot be changed or shifts are delayed
- Auto stop-start disabled or engine restarts immediately
Common causes
- Fluid loss at the reservoir cap or hydraulic power unit seals Most likely
- Worn pump motor or faulty pump relay Possible
- Damaged wiring, connectors or power supply of the pump Possible
- Transmission control module fault Less likely
How to diagnose P0942
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: hydraulic pressure unit, tcm.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 9
- Transmission
- 42
- Specific fault
Questions drivers ask
Can I drive with code P0942?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0942?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.