Fault code P0551 – power steering pressure sensor circuit range/performance

Fault code P0551 is called “Power Steering Pressure (PSP) Sensor Circuit Range/Performance” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0551

OBD-II error code P0551 is a generic code that is defined as a power steering pressure sensor circuit performance range mismatch. It is set when the Powertrain Control Module (PCM) cannot receive a normal signal from the pressure sensor.

Fault code P0551 – power steering pressure sensor circuit range/performance

Modern power steering systems are adaptive. The power steering increases at low speeds and decreases or completely disengages at higher speeds.

This is done to improve feedback through the suspension and steering systems. The advantage of this approach is that the directional controllability of the vehicle is improved. Because sudden or excessive steering forces are largely prevented.

The PCM uses the signal voltage from the power steering pressure sensor to calculate the increase in engine speed. This prevents the engine from stalling at low speeds.

In addition, sufficient steering support is created through effective engine speed control. To make low speed maneuvering possible without excessive application of force to the steering wheel.

If the PCM receives a non-conforming performance range signal from the power steering pressure sensor, it will set the code P0551. The warning lamp may then illuminate, which may require several failure cycles.

Symptoms of vehicle malfunctions

The main signal that an error P0551 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will illuminate (the code will be stored as a fault).
  2. The engine may stall when turning the steering wheel at low engine speeds.
  3. The steering wheel is very difficult or nearly impossible to turn at low speeds.
  4. The power steering pump may make a noise, howling, whistling, or tapping noise.
  5. In some cases, there may be no symptoms other than a stored fault code.

The P0551 error is quite serious, as it can cause steering problems if it occurs. Therefore, when a fault is detected, it is recommended that the error be corrected as soon as possible.

Factors that can cause this error code

The error code P0551 can mean that one or more of the following problems have occurred:

  • Faulty power steering pressure sensor.
  • Broken, damaged, corroded wiring harness.
  • Problem with connector or its contacts.
  • Faulty relay or blown fuse.
  • Low fluid level due to leaks in system.
  • Power steering pump failure.
  • Mechanical failure of the rack and pinion system.
  • Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P0551

Some suggested steps for troubleshooting and fix the error code P0551:

  1. Check that the hydraulic fluid level is normal.
  2. Check the power steering pressure sensor.
  3. Inspect the wires and connection connectors for damage.
  4. Test the power steering pump as well as the rack and pinion gear.
  5. If the error persists, check the PCM module.

Diagnose and repair of problems

If error P0551 occurs, the first step is to check the level and appearance of the fluid in the steering system reservoir. If the level in the reservoir is significantly below the mark, then there is a leak in the system. Therefore, it must be detected and repaired before the vehicle is put back into service.

If the fluid is dark in color or has a burning odor, it has reached the end of its service life and should also be replaced according to the instructions in the manual. Keep in mind that this code can be caused either by low fluid levels or by spoiled fluid, so take the time to do this check.

Checking the wiring

After checking the fluid level and proper condition, there should be no leaks in the system. Next, listen for any strange mechanical noises when the engine is running or when the steering wheel is turning from side to side.

Now perform a thorough visual inspection of all associated wiring and connectors. Look for damaged, burned, shorted, disconnected or corroded wiring and connectors. If necessary, repair if such damage is found.

Remove code P0551 after the operations done, and test-drive the vehicle at low speed. You can also turn the steering wheel from side to side with the engine running to check if the code returns.

Check with a voltmeter

If the code remains, but there is no visible damage to the control wiring. Prepare to perform reference voltage, continuity, resistance, and ground tests on all associated wiring.

When testing the wiring, remember to disconnect the sensor from the PCM to prevent damage to the controller. Compare all readings obtained with those in the manual, and if any abnormalities are found, repair or replace the wiring.

In addition to the wiring, test the pressure sensor itself, as it is part of the control circuit. Replace the sensor if its resistance differs from the value in the manual.

Check the pressure in the power steering

If the malfunction still remains, check the actual pressure developed by the power steering pump. Compare the test results with the values indicated in the manual.

Keep in mind that replacing the power steering pump is technically difficult in most cases. Therefore, it is better to contact professional mechanics.

Therefore, if it is determined that the pump is not working to specifications. Your best bet is to refer the vehicle to a dealer or other competent repair shop for professional assistance.

If the steering wheel turns at low speed just as it was before the code appeared, the problem is unlikely to be related to the pressure generated by the pump. In this case, the problem is most likely related to intermittent electrical problems. Which can sometimes be extremely difficult to find and permanently repair.

One of the typical causes of recurring problems is directly related to cheap, non-original pressure sensors of uncertain origin. And in many cases, the problem can be solved by replacing the pressure sensor with an OEM part.

There is also the possibility that abnormal system voltage can damage the PCM. If this is the case, replace the PCM, reprogram it, and test the vehicle. To see if error code P0551 returns.

On which vehicles does this problem occur most frequently

Fault code P0551 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Chrysler (PT Cruiser)
  • Citroen
  • Dodge (Dakota, Durango, Neon, RAM)
  • Hyundai (Tucson)
  • Infiniti
  • Jeep (Liberty)
  • Kia
  • Lexus
  • Mazda
  • Mitsubishi (Endeavor, Grandis, L200, Pajero, Space Star)
  • Nissan
  • Peugeot
  • Skoda (Octavia)
  • Toyota
  • Volkswagen

Fault code P0551 can sometimes be found with other errors. The most common are the following: P0137, P0171, P0300, P0301, P0308, P0420, P0441, P0455, P0550, P0552, P0553, P0554, P0605, P0700, P1195, P1599.

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