Cause
Low hydraulic fluid level
Not enough fluid in a hydraulic circuit to let its pump build and hold pressure — the simplest cause in this system and the one to eliminate before any of the more interesting ones. It is worth stating plainly because the codes it produces name pumps, pressure units and cycling periods, and none of those words suggests checking a level.
The signature is a pump working harder and more often than it should. A pump cycling at short intervals is refilling an accumulator that is losing charge, and losing pressure through an aerated or insufficient fluid supply does exactly that. A cycling-period code is a level and leak question first — it is telling you the pump cannot keep up, not that the pump is failing.
Aeration is the part people miss. A level low enough to let the pickup draw air intermittently gives worse behaviour than a level that is simply low, because air compresses and the circuit becomes spongy and unpredictable — so the fault comes and goes with cornering, gradient and temperature. And a low level always has a reason: these are sealed circuits, so topping one up without finding the leak means meeting the same codes again, usually sooner.
Typically an easy fix. Often worth checking before paying anyone to look.
Some of these codes mean you should stop driving
1 of the 5 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 (5)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0942 Hydraulic Pressure Unit Likely for this code High
- P0943 Hydraulic Pressure Unit Cycling Period Too Short Likely for this code High
- P0944 Hydraulic Pressure Unit Loss of Pressure Likely for this code Stop driving High
- P0933 Hydraulic Pressure Sensor Range/Performance High
- P0934 Hydraulic Pressure Sensor Circuit Low High
Information, not instruction
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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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