P0550 The computer is not getting a usable signal from the power steering pressure sensor or switch.

Power steering pressure sensor circuit malfunction

P0550 in short

P0550 means the engine computer is not receiving a proper signal from the power steering pressure sensor or switch on a hydraulic steering system. The sensor, its wiring or connector, or low fluid and a failing pump are the usual suspects. Steering may feel heavy at low speed, so have it inspected soon.

The engine computer watches a pressure sensor or switch on the power steering pump. P0550 is the generic title "Power Steering Pressure Sensor Circuit Malfunction".

The computer uses this signal to raise idle speed when the steering is loaded, so the engine does not stall at parking speeds. Delaware's generic code list and TroubleCodes.net give the same meaning for this code.

Causes come from TroubleCodes.net's probable-cause line. Specific fixes and test values vary by vehicle, so use the service information for your car.

Most likely causes

These are general causes for this code across vehicles. None is specific to one make or model.

  1. Damaged, corroded or disconnected wiring or connector

    Common general cause
    Why it ranks here
    TroubleCodes.net lists wiring and connections as a probable cause for this circuit code, and wiring is cheapest to check first.
    What would change this
    Rises if the connector is loose, corroded or the harness is chafed near the pump. Falls if reference voltage, ground and signal test normal.

  2. Power steering pressure sensor or switch

    Common general cause
    Why it ranks here
    The sensor or switch itself is listed as a probable cause by TroubleCodes.net.
    What would change this
    Rises if wiring tests good and the sensor reading does not change with steering load. Falls if the reading follows the steering normally.

  3. Low power steering fluid or a worn pump or steering gear

    Common general cause
    Why it ranks here
    TroubleCodes.net lists low fluid from leaks, pump failure and rack or steering-gear failure as causes for this code, and its first check is the fluid level and condition.
    What would change this
    Rises if the fluid is low or dirty, the pump whines, or fluid is leaking. Falls if fluid level and pump pressure are normal.

  4. Engine control module

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists the computer last; it is rare compared with the wiring and sensor, so it ranks last until those are cleared.
    What would change this
    Rises only after wiring and sensor are both proven good. Falls if repairing the wiring or sensor clears the code.
    How to test the engine control module (ecm / pcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all stored codes and freeze-frame data, and note whether other power steering or engine codes are stored with P0550.

    Low riskTool: OBD-II scan tool

    • IfOther power steering or engine codes are stored too

      It meansDiagnose those together; the circuit or computer may be the shared cause.

      Go to step 2

    • IfP0550 is the only code

      It meansCheck the sensor circuit next.

      Go to step 2

  2. Look over the power steering fluid level and condition, and inspect the sensor connector and wiring at the pump for damage, corrosion or leaks.

    Best left to a shopTool: flashlight, multimeter

    Warning:The steering pump sits near belts and hot or moving parts, and hydraulic fluid can be hot and slippery. Let a shop do the inspection and any electrical testing.

Symptoms

  • Check engine light
  • Engine stalls when the steering wheel is turned at low speed Gets more serious: stop and have it checked.
  • Steering hard to turn when parking or at low speed Gets more serious: stop and have it checked.
  • Whining or screeching from the power steering pump

How to fix

This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.

Parts and cost context

  • Engine control module (ECM / PCM):A control module is the last item to suspect. Labour varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Buick

  • 2004–2005 · Rainier

    Supported by vehicle data

    Buick bulletin 040421004 covers flashing 4WD switch indicator lights and inoperative 4WD with C0327 and P0550 set. Whether it is still current is not verified.

  • 040421004-buickStatus unverified

    Buick bulletin: 4WD switch indicator lights flashing, 4WD inoperative, codes C0327 and P0550

    2004–2005rainier · issued · NHTSA 10017442

    Buick bulletin 040421004 for the 2004-2005 Rainier. The summary says the 4WD switch indicator lights flash and 4WD is inoperative, with codes C0327 and P0550 set. Only the NHTSA summary was read, not the full bulletin; the summary does not give the repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2002–2005 · Trailblazer

    Supported by vehicle data

    Chevrolet bulletin 040421004 covers flashing 4WD switch indicator lights and inoperative 4WD with C0327 and P0550 set. Whether it is still current is not verified.

  • 040421004-chevroletStatus unverified

    Chevrolet bulletin: 4WD switch indicator lights flashing, 4WD inoperative, codes C0327 and P0550

    2002–2005trailblazer · issued · NHTSA 10017442

    Chevrolet bulletin 040421004 for the 2002-2005 TrailBlazer. The summary says the 4WD switch indicator lights flash and 4WD is inoperative, with codes C0327 and P0550 set. Only the NHTSA summary was read, not the full bulletin; the summary does not give the repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

GMC

  • 2002–2005 · Envoy

    Supported by vehicle data

    GMC bulletin 040421004 covers flashing 4WD switch indicator lights and inoperative 4WD with C0327 and P0550 set. Whether it is still current is not verified.

  • 040421004-gmcStatus unverified

    GMC bulletin: 4WD switch indicator lights flashing, 4WD inoperative, codes C0327 and P0550

    2002–2005envoy · issued · NHTSA 10017442

    GMC bulletin 040421004 for the 2002-2005 Envoy. The summary says the 4WD switch indicator lights flash and 4WD is inoperative, with codes C0327 and P0550 set. Only the NHTSA summary was read, not the full bulletin; the summary does not give the repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

No curated relationships for P0550 yet.

All Power steering and steering sensors codes

P0550 questions

Is it safe to drive with P0550?

Steering is a safety system. If the steering feels normal, drive carefully and book an inspection soon. If it gets hard to turn or the engine stalls when you turn, stop and get it towed.

Sources and review

  1. P0550 trouble code definition — TroubleCodes.net
  2. On-Board Diagnostic Trouble Codes (generic code title list) — Delaware Division of Motor Vehicles
  3. 040421004: Buick bulletin: 4WD switch indicator lights flashing, 4WD inoperative, codes C0327 and P0550 — Buick
  4. 040421004: Chevrolet bulletin: 4WD switch indicator lights flashing, 4WD inoperative, codes C0327 and P0550 — Chevrolet
  5. 040421004: GMC bulletin: 4WD switch indicator lights flashing, 4WD inoperative, codes C0327 and P0550 — GMC
Last reviewed
Written by
Saurabh K.
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