Power Steering Pressure Sensor Circuit Malfunction
The PCM has detected a fault in the power steering pressure sensor circuit.
Code Set Parameters
The PCM has failed to receive a voltage input signal from the power steering pressure sensor that is proportionate to the steering angle sensor input signal. This problem normally occurs more frequently at low vehicle speeds. Some vehicle models will require multiple ignition cycles with a failure of this nature for a check engine soon lamp to be illuminated but a code should be stored on the initial failure. If only the initial failure is exhibited, the code may be stored as a “pending code”.
Symptoms may include power steering fluid leakage, engine stalling during low speed maneuvers, a decrease in fuel efficiency, an illuminated service engine soon lamp, and a stored trouble code. In rare cases, the driver may experience no adverse drivability symptoms.
The most common cause of this code being stored is a defective power steering pressure sensor. Other causes may include shorted or open electrical circuitry and connectors, power steering pump or rack and pinion failure, and substandard power steering fluid.
Because the engine tends to stall during low speed driving maneuvers, the idle air control system (specifically replacement of the idle air control motor) is often blamed for the symptoms of this code.
- The power steering pressure sensor is designed to provide the PCM with an input signal reflecting the degree of steering effort required to perform a given vehicle maneuver during low speed conditions
- The PCM uses this input signal for the purpose of calculating the engine RPM level needed to smoothly and effortlessly steer the vehicle
- The PCM then makes make the necessary adjustments
- At low speeds (particularly when parking) the vehicle requires greater power steering assistance in order to maneuver
- This demands that the engine RPM level be increased (as engine RPM level increases, power steering pump RPM level increases, resulting in greater power steering pressure/assistance)
- At high speeds, lower degrees of power steering assistance are required to steer the vehicle
- Most late model vehicles are equipped with variable assist power steering pumps and rack and pinion units which vary power steering pressure in order to provide less pressure
- This promotes decreased exhaust emissions and increased fuel efficiency
- The power steering pressure switch is normally of the pressure sensitive contact, or pressure sensitive resistor, variety
Several tools will be instrumental in successfully diagnosing this code
- A suitable OBD-II scanner (or code reader) and a digital volt/ohmmeter will be most helpful in performing a successful diagnosis
Begin with a visual inspection of all wiring and connectors
- Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
- Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- Continue by clearing the code and operating the vehicle to see if it returns
- This will help to determine whether or not the malfunction is intermittent
After the codes are cleared, test drive the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made
Proceed with your diagnosis with a visual inspection of the power steering system
- Make sure that there are no fluid leaks and that power steering fluid is clean and of the correct type
- Visually inspect the power steering pressure sensor, as well as the electrical wiring and connectors for signs of damage from corrosion, burning, or fluid contamination
- Repair or replace faulty components as required.
If the power steering fluid is clean and there are no leaks present and no wiring or connectors are damaged, then connect the scanner (or code reader) and make a note of all stored codes and relevant freeze frame data
- Test drive the vehicle and see if the code persists; if it does, then proceed with the diagnostic strategy.
Disconnect the power steering pressure sensor connector and check sensor resistance using the digital volt/ohmmeter
- Compare your findings with manufacturer’s specifications and dispose of the sensor if actual readings do not conform
- If the sensor checks out, test the sensor connector for voltage and ground signals
- If no voltage and ground signals are detected, disconnect the PCM connector and perform a continuity test on the entire circuit in order to isolate a possible malfunction and repair open or shorted wiring as required
If voltage and ground signals are present, connect the manual power steering pressure gauge
- Use caution when testing system pressure, as levels can reach the extremes
- Consult your vehicle’s service manual and compare your findings, replace or repair power steering system components as needed.