Faulty power steering pressure sensor or switch (internal failure or stuck signal); Damaged, chafed or corroded wiring to the sensor, including open circuit or short to earth or supply; Poor connection at the sensor plug (corrosion, loose or spread terminals, oil contamination); Low, aerated or contaminated power steering fluid, or a leak affecting pressure at the sensor; Worn power steering pump or restriction in the hydraulic circuit giving abnormal pressure readings; Fault in the engine control unit input circuit.

P0550

Power Steering Pressure Sensor/Switch Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
5: AreaVehicle speed, idle control and auxiliary inputs
50: FaultThe specific fault in that area

What it means

P0550 is the generic code for a fault in the power steering pressure sensor or switch circuit. The engine control unit uses this signal to know when the hydraulic power steering is under heavy load, so it can raise idle speed or add throttle to stop the engine stalling or dipping. The code sets when the signal is out of range, stuck, or does not change as expected when the steering is turned.

Symptoms

Engine idle dips, hunts or stalls when turning the wheel at low speed or parking
Rough or unstable idle with the steering on full lock
Idle speed does not rise when the steering is turned
Heavy or inconsistent steering feel on some vehicles
Engine warning light on, possibly with no other noticeable change

Possible causes

Faulty power steering pressure sensor or switch (internal failure or stuck signal)likely
Damaged, chafed or corroded wiring to the sensor, including open circuit or short to earth or supplylikely
Poor connection at the sensor plug (corrosion, loose or spread terminals, oil contamination)likely
Low, aerated or contaminated power steering fluid, or a leak affecting pressure at the sensorpossible
Worn power steering pump or restriction in the hydraulic circuit giving abnormal pressure readingspossible
Fault in the engine control unit input circuitrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, then check for related idle or other sensor codes
Check the power steering fluid level and condition, and look for leaks around the pump, hoses and sensor
Inspect the sensor, its connector and the wiring back to the control unit for chafing, oil soaking, corrosion and damage
With the sensor connected, watch the live data or signal while turning the steering from centre to full lock and back, and check it changes smoothly and as expected
Check the sensor supply, earth and signal wiring with a multimeter against the manufacturer's wiring diagram for your model
Check the idle speed response to steering load and compare with the expected behaviour for the engine
Check the power steering system pressure with a gauge if the sensor reading looks wrong but the circuit tests good
Clear the code and road test to see if it returns once the fault is repaired

How to fix

Replace the power steering pressure sensor or switch if it is faulty or stuck
Repair or replace damaged wiring and fix any open circuit or short
Clean, repair or replace the connector and terminals where corrosion or poor contact is found
Correct fluid level, replace contaminated fluid and repair any leaks as needed
Repair or replace the power steering pump or faulty hydraulic components if pressure is abnormal
Diagnose and repair the control unit only after all wiring and the sensor are proven good

Can I keep driving?

Low severity

The car can usually be driven while you arrange a repair, but take care at low speeds and when parking as the engine may dip or stall under steering load. If the steering becomes heavy or the engine stalls repeatedly, limit driving until it is checked.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.