Cause
Faulty hydraulic pump relay
The relay switching the pump that pressurises an automated clutch or gearbox. The pump cycles frequently by design, so this relay switches far more often than most — contact wear is expected, and it is the cheapest thing to eliminate before the pump is suspected.
Typically an easy fix. Often worth checking before paying anyone to look.
Some of these codes mean you should stop driving
1 of the 6 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (6)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0945 Hydraulic Pump Relay/Control Circuit/Open Likely for this code High
- P0946 Hydraulic Pump Relay/Control Circuit Range/Performance Likely for this code High
- P0947 Hydraulic Pump Relay/Control Circuit Low Likely for this code High
- P0948 Hydraulic Pump Relay/Control Circuit High Likely for this code High
- P0942 Hydraulic Pressure Unit High
- P0944 Hydraulic Pressure Unit Loss of Pressure Stop driving High
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.
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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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