Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P0550 Power Steering Pressure Sensor/Switch Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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. P0550 is the general circuit fault. No manufacturer document available to us uses it. Without the signal the engine can drop or stall at full lock, or the module raises idle permanently as a substitute.

Likely causes

Connector or wire open or corroded (splash zone at the pump)
Sensor or switch faulty, often also leaking
5 V reference or ground disturbed
Engine module

Symptoms

  • Check engine light (depending on the maker)
  • Idle drops when steering at standstill, engine may stall
  • Raised idle (substitute value)

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–250
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

power steering pressure switchsensor wiringengine control module

Related codes

P0551P0552P0553P0554P0506

References: saabwisonline.com, law.cornell.edu.