General fault of the unit that generates and stores hydraulic pressure for an automated gearbox or its auxiliary oil supply: motor-driven pump, accumulator and pressure control. Toyota sets P0942 on the 2001 to 2005 MR2 Spyder sequential gearbox 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.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- Transmission or gearbox 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
Most likely causes
- Fluid loss at the reservoir cap or hydraulic power unit seals
- Worn pump motor or faulty pump relay
- Damaged wiring, connectors or power supply of the pump
- Transmission control module fault
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P0942 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 9: Transmission
- 42: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0942?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P0942?
The most common causes are: fluid loss at the reservoir cap or hydraulic power unit seals; worn pump motor or faulty pump relay; damaged wiring, connectors or power supply of the pump.
Related codes
- P0943Hydraulic Pressure Unit Cycling Period Too Short
- P0944Hydraulic Pressure Unit Loss of Pressure
- P0945Hydraulic Pump Relay/Control Circuit/Open
- P0946Hydraulic Pump Relay/Control Circuit Range/Performance
- P094CHydraulic Pump Performance/Stuck Off
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.