P0942: Hydraulic Pressure Unit
What to do
The gearbox may stop working entirely, and if it does, the car is not driveable — there is no mechanical backup on this kind of transmission. Have it recovered. The car itself is usually fine; it simply has no way to select or hold a gear.
What this code means
A general fault in the hydraulic power unit — the pump and accumulator assembly that supplies the pressure to operate an automated manual or dual-clutch gearbox.
This unit is the single point of failure for the whole transmission on these designs. Every clutch movement and every gear engagement depends on it, so unlike a conventional automatic — which has a mechanical pump driven by the engine and will at least limp home on default hydraulics — an actuation system that loses its pump stops the gearbox completely. There is no mechanical fallback because there is no mechanical connection to fall back on.
That concentration of dependence is worth knowing before the symptoms arrive, because it explains why a fault here immobilises a car that has nothing mechanically wrong with it.
Likely causes
Start here
- Faulty hydraulic power unit · specialist
- Hydraulic system leak · specialist
- Low hydraulic fluid level · easy
Less common
- Failed accumulator charge · specialist
- Faulty hydraulic pump relay · easy
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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