FORD 1484948 POWER STEERING PRESSURE SENSOR

The Quattro Freni QF24E00005 is a hydraulic power steering pressure switch (also referred to as a PSP switch or power steering pressure sensor). It is installed on the high-pressure side of the power steering system — either directly on the pump body or in-line on the high-pressure hose — and monitors hydraulic fluid pressure in real time.

When the driver turns the steering wheel at low speed or performs stationary manoeuvres, the power steering pump generates a sharp rise in hydraulic pressure. The QF24E00005 detects this pressure spike and sends a signal to the Engine Control Unit (ECU / PCM). In response, the ECU raises idle speed — via the idle air control valve or electronic throttle — to compensate for the additional mechanical load on the engine, preventing RPM drop and stalling.

The switch operates as a simple two-wire on/off device: below a set pressure threshold it remains open; above the threshold it closes and completes the ECU signal circuit. No analogue output is involved — only a binary switched state. This makes the part robust and reliable, with no electronic calibration required after installation.

• Engine RPM drops noticeably when turning the steering wheel at idle or low speed — most obvious during slow parking manoeuvres
• Engine stalls during full-lock turns at very low speed or when stationary with the wheel turned hard over
• Check Engine / MIL warning light illuminated; OBD scanner reads P055x codes related to the PSP switch circuit
• Fluctuating or hunting idle when steering input is applied, with the engine recovering once the wheel is released
• Visible power steering fluid leak at the switch body or at the electrical connector pins — a sign of internal diaphragm failure causing fluid wicking through the connector

Based on OEM cross-reference numbers listed on this page. Always verify the part number against your vehicle’s VIN before ordering. Fitment may vary by engine variant and production date.

1. Drain or siphon the power steering reservoir before starting. Removing the switch under full system pressure will cause an immediate fluid spill. A turkey baster or hand pump removes most fluid in under two minutes and protects hot engine components from contamination.
2. Disconnect the wiring connector first. Press the locking tab and pull straight rearward — do not twist. The connector tab is plastic and breaks easily if levered sideways. If stiff from age, a small amount of electrical contact cleaner around the tab will free it.
3. Use a 19 mm deep-well socket (or a 19 mm crowfoot wrench). Hold the high-pressure line fitting with a second spanner to prevent twisting the hose during removal. On Focus Mk1/Mk2 with the switch on the pump body, a deep-well socket with a short extension is sufficient.
4. Inspect the seating surface on the pump port or pressure line before installation. Remove any dried sealant, debris, or corrosion. The switch seals on a metal-to-metal tapered seat with an O-ring — any contamination will cause an immediate leak.
5. Torque to 20 Nm (177 lb-in). This is the Ford-specified value per the Focus Service Manual. Overtightening crushes the internal diaphragm and causes the seat to leak. Use a calibrated torque wrench — do not rely on feel.
6. Refill the reservoir and bleed the system. Start the engine and turn lock-to-lock 5–6 times at idle. Top up as required after bleeding.
   Fluid by brand:
   — Ford Focus / C-Max: Mercon ATF / Dexron II equivalent (Ford XT-2-QDX)
   — Volvo S40 II / V50 / C30: ATF per owner’s manual (Dexron II or III equivalent)
   — Mazda 3 BL: Mazda ATF M-III or equivalent (Dexron III)
7. Clear OBD fault codes with a scanner and allow the engine to reach operating temperature. Steer lock-to-lock once more. Codes P0550–P0553 must not return. If they do, inspect the connector and harness for corrosion before condemning the replacement switch.