P0551Power Steering Pressure Sensor/Switch Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Hydraulic power steering has a pressure switch or sensor on the high-pressure line; when the wheel is turned at standstill, pump pressure and engine load rise sharply, so the engine module raises idle air in advance to stop the engine stalling. That makes it an input to idle control under CARB. Switches (Saab, Mitsubishi) ground a pull-up; analogue 5 V sensors (Toyota) give about 0.45 V at zero pressure. GM's and Ford's tables do not use P0550–P0554. P0551 means the switch reports high pressure where that is implausible – at speed there is hardly any steering. Mitsubishi sets it when the switch stays on through 10 drive-and-stop cycles; Saab's Trionic T8 after 600 s above 50 km/h, keeping raised idle as substitute and without warning lamp.
- What you may notice
- Permanently slightly raised idle
- No load compensation when steering
- Check engine light depending on the maker (Saab: none)
- Likely causes
- LikelyPressure switch stuck closed or faulty internally
- PossibleSignal line shorted to ground (ground means active)
- RarePermanently high pressure (steering valve sticking, kinked line)
- RareVehicle speed signal faulty (Saab depends on P0501)
- Inspection (ITP)
- Can matter for the ITP: it concerns the emissions system.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.