🏎️ Power Steering Pressure Sensor Problem (DTC Code P0550)

❓ What Does This Mean?

Diagnostic code P0550 is a generic OBD-II code that applies to vehicles equipped with a power steering pressure sensor. It is often found on brands like Infiniti, Nissan, Toyota, Lexus, Mazda, Dodge, Chrysler, Jeep, Kia, etc.

📌 Role of the Power Steering Pressure Sensor

Before the invention of power steering systems, vehicles used non-assisted rack and pinion steering, which made low-speed driving difficult.

Hydraulic or electric power steering systems now allow pressure to be adjusted according to needs. The Engine Control Module (ECM) or Powertrain Control Module (PCM) monitors the pressure and adjusts it accordingly using the power steering pressure sensor.

When a problem is detected in the sensor circuit, the ECM illuminates the check engine light and records a Diagnostic Trouble Code (DTC).

🛑 Severity of Code P0550

The power steering system may continue to function, but prolonged failure can complicate driving and increase repair costs.

---

⚠️ Symptoms of Code P0550

🔴 Irregular idle
🔴 Engine stalling
🔴 Intermittent steering (jerky turning)
🔴 Difficulty turning the steering wheel
🔴 Groaning noises when steering
🔴 Power steering fluid leak
🔴 Poor handling

---

🔍 Possible Causes of Code P0550

🔧 Broken or damaged wiring harness
🔧 Power steering fluid leak
🔧 Faulty fuse or relay
🔧 Faulty power steering pressure sensor
🔧 Problem with the ECM
🔧 Damaged connector or pin (corrosion, melting, broken locking tab, etc.)

---

🛠️ Diagnostic and Repair Steps

✅ 1. Check Technical Service Bulletins (TSBs)

Before any intervention, consult the TSBs to see if an official fix exists for your vehicle.

✅ 2. Recommended Tools

• 🔧 OBD-II code reader
• 🛢 Power steering fluid
• 🔬 Multimeter
• 🔩 Socket and ratchet set
• 🔌 Battery terminal cleaner
• 📖 Vehicle service manual

✅ 3. Basic Checks

✔ Check the power steering fluid level

• Top up if necessary.
• Look under the vehicle for possible leaks.

✔ Inspect the power steering pressure sensor

• Ensure there is no leak at the sensor.
• Check that it is not damaged or worn.

✔ Inspect the electrical connector

• Check for signs of corrosion, oil, or melting.
• Clean the connector before reconnecting it.

🚨 WARNING: These systems operate under high pressure. A pressurized leak can be dangerous. If you are unsure, consult a professional mechanic.

✅ 4. Test the Pressure Sensor

• Refer to the service manual for test values.
• Locate the pressure sensor mounted on the high-pressure line.
• Test the sensor using a multimeter to verify if it is functioning correctly.

✅ 5. Check the Electrical Circuit

• Disconnect the battery before any electrical repair.
• Disconnect the sensor and ECM, then test the circuits with a multimeter.
• If everything seems correct, the problem may be related to the sensor or ECM.

If the problem persists after these checks, it is recommended to take the vehicle to a specialized workshop.

---

🚨 Safety Tips

✅ Let the engine cool down before any intervention.
✅ Block the wheels to prevent unintended movement.
✅ Wear personal protective equipment (PPE).
✅ Do not handle hydraulic circuits under pressure.

What Does It Mean?

This generic powertrain diagnostic trouble code (DTC) generally applies to all OBD-II equipped vehicles with a power steering pressure sensor. This may include, but is not limited to, Infiniti, Nissan, Toyota, Lexus, Mazda, Dodge, Chrysler, Jeep, Kia, etc. vehicles.

Before the invention of hydraulic and electric power steering systems, manufacturers used an unassisted rack and pinion steering system. This made low-speed steering extremely difficult and inefficient.

For this reason, we invented the power steering system. Generally, a hydraulic assist system will include a belt-driven power steering pump, a rack and pinion/steering gearbox, and various hoses/lines and sensors. The Engine Control Module (ECM) or Powertrain Control Module (PCM) works in conjunction with the power steering pressure sensor to monitor the pressure in the system and adjust it accordingly.

The ECM illuminates the check engine light with P0551 and related codes when it recognizes one or more conditions outside of a specific desired range in the power steering pressure sensor circuit. Most of the time, I would say this code is set by the ECM due to an electrical issue, but sometimes, mechanical problems can be the cause.

P0551 Power Steering Pressure Sensor Circuit Range/Performance code is set when the ECM/PCM monitors a condition outside of specific parameters in the sensor circuit. It is one of five related codes, which are P0550, P0551, P0552, P0553, and P0554.
How severe is this DTC?

Since most likely, your power steering system could fail completely and you could still drive your car, the severity here is set to low. Obviously, this is a foolish idea, any problem left long enough will cost you more in the long run.

An example of a power steering fluid pressure switch/sensor:

What are some of the symptoms of the code?

Symptoms of a P0551 diagnostic code may include:

Irregular idle

Symptoms

of engine stalling
Intermittent power assist when steering (jerky turning)
Vehicle hard to steer
Whining noises
Leaking fluid
Poor handling

What are some of the common causes of the code?

Causes

of this code may include:

Broken or damaged wiring harness
Power steering fluid leak
Faulty fuse/relay
Faulty power steering pressure sensor
ECM problem
Pin/connector issue. (e.g., corrosion, melting, broken locking tab, etc.)

What are the P0551 troubleshooting steps?

Be sure to check the Technical Service Bulletins (TSBs) for your vehicle. Accessing a known fix can save you time and money during diagnosis.
Tools

Some of the things you might need when diagnosing or repairing power steering circuits and systems:

OBD code reader
Power steering fluid
Drain pan
Multimeter
Basic socket set
Ratchet and wrench sets
Basic screwdriver set
Battery terminal cleaner
Service manual

Safety Tips

Let the engine cool down
Chock the wheels
Wear PPE (Personal Protective Equipment)

NOTE: ALWAYS check and record the integrity of your battery and charging system before proceeding with troubleshooting.
Basic Step #1

Always keep it simple at first. Check your power steering fluid level and top it up if necessary. Check your parking spot, any signs of a leak? If so, investigate further. If the fluid is low, it’s going somewhere, so be sure to repair any mechanical leak before proceeding with any electrical diagnosis. Look closely at the sensor itself, I have personally seen these sensors leak through the sensor itself, so make sure it is dry and there are no obvious signs of damage and/or leaks.

NOTE: These systems use high pressures that could cause injury, so be careful, pinhole leaks are dangerous and pose a serious hazard. If you are not familiar with the dangers of working with hydraulic systems, please take your vehicle to a reputable repair center.
Basic Step #2

To rule out the sensor, you will need to test it. Refer to your service manual for the necessary specifications. Usually, the sensor itself is mounted on a power steering pressure line. Most of the time, these are hard aluminum/braided rubber lines and are accessible under the hood.

NOTE: A common leak is where the rubber meets the hard pressure line, sometimes it separates and causes a leak that is hard to find.
Basic Tip #3

Locate the electrical connector on the pressure sensor. Inspect for any oil residue/soaking. If the connector is soaked in oil, the leak is obviously a problem but the oil must be cleaned off before reconnecting. A connector showing signs of melting and/or corrosion should be repaired.

NOTE: Be sure to disconnect the battery before performing any electrical repairs.
Basic Step #4

Check for physical damage. In this case, I would say the sensor is exposed to harsh conditions. If the lines are not properly secured, the sensor can rub against something and over time can cause some kind of electrical issue. Secure any loose lines, especially the one with the sensor mounted on it.
Basic Step #5

You may be able to check the integrity of the power steering pressure sensor circuit(s). To rule out pretty much any issue with your wiring harness, you can disconnect the circuit from both the sensor and the ECM. Using your multimeter, refer to your service manual and verify that all desired values are checked. If everything seems okay up to this point, I recommend taking the vehicle to your reputable repair center.

What Does It Mean?

This generic powertrain diagnostic trouble code (DTC) generally applies to all OBD-II equipped vehicles with a power steering pressure sensor. This may include, but is not limited to, Infiniti, Nissan, Toyota, Lexus, Mazda, Dodge, Chrysler, Jeep, Kia, etc. vehicles.

Before the invention of hydraulic and electric power steering systems, manufacturers used an unassisted rack and pinion steering system. This made low-speed steering extremely difficult and inefficient.

For this reason, we invented the power steering system. Generally, a hydraulic assist system will include a belt-driven power steering pump, a rack and pinion/steering gearbox, and various hoses/lines and sensors. The Engine Control Module (ECM) or Powertrain Control Module (PCM) works in conjunction with the power steering pressure sensor to monitor the pressure in the system and adjust it accordingly.

The ECM illuminates the check engine light with P0552 and related codes when it recognizes one or more conditions outside a specific desired range in the power steering pressure sensor circuit. Most of the time, I would say this code is set by the ECM due to an electrical issue, but sometimes, mechanical problems can be the cause.

P0552 Power Steering Pressure Sensor Circuit Low code is set when the ECM/PCM monitors an electrical value lower than desired in the input circuit. This is one of five related codes, which are P0550, P0551, P0552, P0553, and P0554.
How severe is this DTC?

Since most likely, your power steering system could completely fail and you could still drive your car, the severity here is set to low. Obviously, this is a foolish idea, any problem left long enough will cost you more in the long run.

An example of a power steering fluid pressure switch/sensor:

What are some of the symptoms of the code?

Symptoms of a P0552 diagnostic code may include:

Rough idle

Symptoms

of engine stalling
Intermittent power assist when steering (jerky turning)
Vehicle hard to steer
Whining noises
Leaking fluid
Poor handling

What are some of the common causes of the code?

Causes

of this code may include:

Broken or damaged wiring harness
Power steering fluid leak
Faulty fuse/relay
Faulty power steering pressure sensor
ECM problem
Pin/connector issue. (e.g., corrosion, melting, broken locking tab, etc.)

What are the troubleshooting steps for P0552?

Be sure to check the Technical Service Bulletins (TSBs) for your vehicle. Access to a known fix can save you time and money when diagnosing.
Tools

Some of the things you might need when diagnosing or repairing power steering circuits and systems:

OBD code reader
Power steering fluid
Drain pan
Multimeter
Basic socket set
Ratchet and wrench sets
Basic screwdriver set
Battery terminal cleaner
Service manual

Safety Tips

Let the engine cool down
Chock the wheels
Wear PPE (Personal Protective Equipment)

NOTE: ALWAYS check and record the integrity of your battery and charging system before proceeding with troubleshooting.
Basic Step #1

Always start simple. Check your power steering fluid level and top it off if necessary. Check your parking spot, any signs of a leak? If so, investigate further. If the fluid is low, it’s going somewhere, so be sure to fix any mechanical leak before proceeding with any electrical diagnosis. Look closely at the sensor itself, I have personally seen these sensors leak through the sensor itself, so make sure it is dry and there are no obvious signs of damage and/or leaks.

NOTE: These systems use high pressures that could cause injury, so be careful, pinhole leaks are dangerous and pose a serious hazard. If you are not familiar with the dangers of working with hydraulic systems, please take your vehicle to a reputable repair center.
Basic Step #2

To rule out the sensor, you will need to test it. Refer to your service manual for the necessary specifications. Usually, the sensor itself is mounted on a power steering pressure line. Most of the time, these are hard aluminum/braided rubber lines and are accessible under the hood.

NOTE: A common leak is where the rubber meets the hard pressure line, sometimes it separates and causes a leak that is hard to find.
Basic Tip #3

Locate the electrical connector on the pressure sensor. Inspect for any oil residue/soaking. If the connector is soaked in oil, the leak is obviously a problem but the oil must be cleaned before reconnecting. A connector showing signs of melting and/or corrosion should be repaired.

NOTE: Be sure to disconnect the battery before performing any electrical repairs.
Basic Step #4

Check for physical damage. In this case, I would say the sensor is exposed to harsh conditions. If the lines are not properly secured, the sensor can rub against something and over time can cause some kind of electrical issue. Secure any loose lines, especially the one with the sensor mounted on it.
Basic Step #5

You may be able to check the integrity of the power steering pressure sensor circuit(s). To rule out pretty much any issue with your wiring harness, you can disconnect the circuit from both the sensor and the ECM. Using your multimeter, refer to your service manual and verify that all desired values are checked. If everything seems okay up to this point, I recommend taking the vehicle to your reputable repair center.

What Does It Mean?

This generic powertrain diagnostic trouble code (DTC) generally applies to all OBD-II equipped vehicles with a power steering pressure sensor. This may include, but is not limited to, Infiniti, Nissan, Toyota, Lexus, Mazda, Dodge, Chrysler, Jeep, Kia, etc. vehicles.

Before the invention of hydraulic and electric power steering systems, manufacturers used an unassisted rack and pinion steering system. This made low-speed steering extremely difficult and inefficient.
For this reason, we invented the power steering system. Generally speaking, a hydraulic assist system will include a belt-driven power steering pump, a rack and pinion/steering gearbox, and various hoses/lines and sensors. The Engine Control Module (ECM) or Powertrain Control Module (PCM) works in conjunction with the power steering pressure sensor to monitor the pressure in the system and adjust it accordingly.

The ECM illuminates the check engine light with P0553 and related codes when it recognizes one or more conditions outside a specific desired range in the power steering pressure sensor circuit. Most of the time, I would say this code is set by the ECM due to an electrical issue, but sometimes, mechanical problems can be the cause.

P0553 Power Steering Pressure Sensor Circuit High code is set when the ECM/PCM monitors an electrical value higher than desired in the input circuit. It is one of five related codes, which are P0550, P0551, P0552, P0553, and P0554.
How severe is this DTC?

Since most likely, your power steering system could fail completely and you could still drive your car, the severity here is set to low. Obviously, this is a foolish idea, any problem left long enough will cost you more in the long run.

An example of a power steering fluid pressure switch/sensor:

What are some of the symptoms of the code?

Symptoms of a P0553 diagnostic code may include:

Rough idle

Symptoms

of engine stalling
Intermittent power assist when steering (jerky turning)
Vehicle hard to steer
Whining noises
Leaking fluid
Poor handling

What are some of the common causes of the code?

Causes

of this code may include:

Broken or damaged wiring harness
Power steering fluid leak
Faulty fuse/relay
Faulty power steering pressure sensor
ECM problem
Pin/connector issue. (e.g., corrosion, melting, broken locking tab, etc.)

What are the troubleshooting steps for P0553?

Be sure to check the Technical Service Bulletins (TSBs) for your vehicle. Access to a known fix can save you time and money during diagnosis.
Tools

Some of the things you might need when diagnosing or repairing power steering circuits and systems:

OBD code reader
Power steering fluid
Drain pan
Multimeter
Basic socket set
Ratchet and wrench sets
Basic screwdriver set
Battery terminal cleaner
Service manual

Safety Tips

Let the engine cool down
Chock the wheels
Wear PPE (Personal Protective Equipment)

NOTE: ALWAYS check and record the integrity of your battery and charging system before proceeding with troubleshooting.
Basic Step #1

Always start simple. Check your power steering fluid level and top it up if necessary. Check your parking spot, any signs of a leak? If so, investigate further. If the fluid is low, it’s going somewhere, so be sure to fix any mechanical leak before proceeding with any electrical diagnosis. Look closely at the sensor itself; I have personally seen these sensors leak through the sensor itself, so make sure it is dry and there are no obvious signs of damage and/or leaks.

NOTE: These systems use high pressures that could cause injury, so be careful; pinhole leaks are dangerous and pose a serious hazard. If you are not familiar with the dangers of working with hydraulic systems, please take your vehicle to a reputable repair center.
Basic Step #2

To rule out the sensor, you will need to test it. Refer to your service manual for the necessary specifications. Usually, the sensor itself is mounted on a power steering pressure line. Most of the time, these are hard aluminum/braided rubber lines and are accessible under the hood.

NOTE: A common leak is where the rubber meets the hard pressure line; sometimes it separates and causes a leak that is hard to find.
Basic Tip #3

Locate the electrical connector on the pressure sensor. Inspect for any oil residue/saturation. If the connector is soaked in oil, the leak is obviously a problem, but the oil must be cleaned off before reconnecting. A connector showing signs of melting and/or corrosion should be repaired.

NOTE: Be sure to disconnect the battery before performing any electrical repairs.
Basic Step #4

Check for physical damage. In this case, I would say the sensor is exposed to harsh conditions. If the lines are not properly secured, the sensor can rub against something and over time can cause some electrical issue. Secure any loose lines, especially the one with the sensor mounted on it.
Basic Step #5

You may be able to check the integrity of the power steering pressure sensor circuit(s). To rule out pretty much any issue with your wiring harness, you can disconnect the circuit from both the sensor and the ECM. Using your multimeter, refer to your service manual and verify that all desired values are checked. If everything seems okay up to this point, I recommend taking the vehicle to your reputable repair center.

What Does It Mean?

This generic powertrain diagnostic trouble code (DTC) generally applies to all OBD-II equipped vehicles with a power steering pressure sensor. This may include, but is not limited to, Infiniti, Nissan, Toyota, Lexus, Mazda, Dodge, Chrysler, Jeep, Kia, etc. vehicles.

Before the invention of hydraulic and electric power steering systems, manufacturers used an unassisted rack and pinion steering system. This made low-speed steering extremely difficult and inefficient.

For this reason, we invented the power steering system. Generally, a hydraulic assist system will include a belt-driven power steering pump, a rack and pinion/steering gearbox, and various hoses/lines and sensors. The Engine Control Module (ECM) or Powertrain Control Module (PCM) works in conjunction with the power steering pressure sensor to monitor the pressure in the system and adjust it accordingly.

The ECM illuminates the check engine light with P0554 and related codes when it recognizes one or more conditions outside a specific desired range in the power steering pressure sensor circuit. Most of the time, I would say this code is set by the ECM due to an electrical issue, but sometimes, mechanical problems can be the cause.

P0554 Power Steering Pressure Sensor Circuit Intermittent code is set when the ECM/PCM monitors an intermittent malfunction in the sensor circuit. This is one of five related codes, which are P0550, P0551, P0552, P0553, and P0554.
How severe is this DTC?

Since most likely, your power steering system could fail completely and you could still drive your car, the severity here is set to low. Obviously, this is a foolish idea, any problem left long enough will cost you more in the long run.

An example of a power steering fluid pressure switch/sensor:

What are some of the symptoms of the code?

Symptoms of a P0554 diagnostic code can include:

Irregular idle

Symptoms

of engine stalling
Intermittent power assist when steering (jerky turning)
Vehicle hard to steer
Whining noises
Leaking fluid
Poor handling

What are some of the common causes of the code?

Causes

of this code can include:

Broken or damaged wiring harness
Power steering fluid leak
Faulty fuse/relay
Faulty power steering pressure sensor
ECM problem
Pin/connector issue. (e.g., corrosion, melting, broken locking tab, etc.)

What are the P0554 troubleshooting steps?

Be sure to check the Technical Service Bulletins (TSBs) for your vehicle. Access to a known fix can save you time and money when diagnosing.
Tools

Some of the things you might need when diagnosing or repairing power steering circuits and systems:

OBD code reader
Power steering fluid
Drain pan
Multimeter
Basic socket set
Ratchet and wrench sets
Basic screwdriver set
Battery terminal cleaner
Service manual

Safety Tips

Let the engine cool down
Chock the wheels
Wear PPE (Personal Protective Equipment)

NOTE: ALWAYS check and record the integrity of your battery and charging system before proceeding with troubleshooting.
Basic Step #1

Always start simple. Check your power steering fluid level and top it up if necessary. Check your parking spot, any signs of a leak? If so, investigate further. If the fluid is low, it’s going somewhere, so be sure to repair any mechanical leak before proceeding with any electrical diagnostics. Look closely at the sensor itself, I have personally seen these sensors leak through the sensor itself, so make sure it is dry and there are no obvious signs of damage and/or leaks.

NOTE: These systems use high pressures that could cause injury, so be careful, pinhole leaks are dangerous and a serious hazard. If you are not familiar with the dangers of working with hydraulic systems, please take your vehicle to a reputable repair center.
Basic Step #2

To rule out the sensor, you will need to test it. Refer to your service manual for the necessary specifications. Usually, the sensor itself is mounted on a power steering pressure line. Most of the time, these are hard aluminum/braided rubber lines and are accessible under the hood.

NOTE: A common leak is where the rubber meets the hard pressure line, sometimes it separates and causes a leak that is hard to find.
Basic Tip #3

Locate the electrical connector on the pressure sensor. Inspect for any oil residue/soaking. If the connector is soaked in oil, the leak is obviously a problem but the oil must be cleaned off before reconnecting. A connector showing signs of melting and/or corrosion should be repaired.

NOTE: Be sure to disconnect the battery before performing any electrical repairs.
Basic Step #4

Check for physical damage. In this case, I would say the sensor is exposed to harsh conditions. If the lines are not properly secured, the sensor can rub against something and over time can cause some electrical issue. Secure any loose lines, especially the one with the sensor mounted on it.
Basic Step #5

You may be able to check the integrity of the power steering pressure sensor circuit(s). To pretty much rule out any issue with your wiring harness, you can disconnect the circuit from both the sensor and the ECM. Using your multimeter, refer to your service manual and verify all desired values are checked. If everything seems okay up to this point, I recommend taking the vehicle to your reputable repair center.

What does it mean?

This is a generic powertrain diagnostic trouble code (DTC) and applies to OBD-II vehicles equipped with a brake booster pressure sensor. This may include, but is not limited to, vehicles from Fiat, Alfa Romeo, Nissan, Ford, Dodge, Pontiac, Chevrolet, Acura, Subaru, Hyundai, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

Fault code P0555 is one of several possible codes associated with the brake booster pressure sensor circuit.

This code indicates that the Powertrain Control Module (PCM) has detected a malfunction affecting the operation of the brake booster pressure sensor circuit. Common codes related to brake booster pressure sensor circuit malfunctions include P0555, P0556, P0557, P0558, and P0559. The specific situation determines which code is triggered by the PCM, and the brake warning light may illuminate or flash during braking.

The purpose of the brake booster pressure sensor circuit is to monitor the amount of pressure (vacuum) applied to the brake booster. The circuit is controlled by the PCM to adapt to various braking conditions and adjust pressure to assist with brake pedal operation. This process is essential for power brakes to function correctly, allowing the vehicle to slow down or stop safely with minimal foot pressure applied to the brake pedal.

Code P0555 is set by the PCM when the brake booster pressure sensor has no output voltage.
How severe is this DTC?
b
The severity of this code varies depending on the specific malfunction, and the severity level will increase if not addressed promptly. At some point, the vehicle’s safety level could become compromised, requiring immediate attention.

Photo of a brake booster pressure (vacuum) sensor:

What are some of the symptoms of the code?

Symptoms of a P0555 fault code may include:

Brake warning light flashing during braking
Brake warning light remains illuminated
Service engine soon light illuminated
Increased effort required to depress the brake pedal

What are some common causes of the code?

Causes

of this P0555 code may include:

Faulty brake booster pressure sensor
Worn or damaged vacuum lines
Corroded or damaged connector
Damaged or faulty wiring
Faulty brake booster
Faulty PCM

What are the troubleshooting steps for P0555?

The first step in the troubleshooting process for any malfunction is to check technical service bulletins for known issues with the specific vehicle.

Locate all components associated with the brake booster pressure sensor circuit. This includes the brake booster pressure sensor, brake booster, vacuum lines, wiring, connectors, and the PCM on a simplex system. Once these components are located, perform a thorough visual inspection to check for any obvious defects such as chafing, rubbing, exposed wires, or burn marks. Connectors should also be inspected for corrosion buildup or damaged pins. Vacuum lines should be checked for security, weather cracking, leaks, and overall service condition.
Advanced Steps

Advanced steps become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and vehicle-specific technical references. Voltage requirements will be highly dependent on the specific year, make, and model of the vehicle.
Circuit Checks

Voltage requirements vary depending on the specific vehicle, the brake booster pressure sensor circuit configuration, and integrated components. Technical data must be referenced to obtain the correct voltage range for the brake booster pressure sensor and the appropriate troubleshooting sequence. Correct input voltage to a sensor with no output voltage is typically an indication of internal failure.

If this process identifies a missing power source or ground, continuity tests may be necessary to verify the condition of the wiring and connectors. Continuity tests are always performed with the circuit power disconnected, and normal readings should be 0 ohms resistance unless otherwise specified by technical data. Resistance or lack of continuity indicates faulty wiring or connectors that are shorted or open and must be repaired or replaced.
Common Repairs

Replacing a faulty brake booster pressure sensor
Cleaning corrosion from connectors
Repairing or replacing wiring
Replacing the brake booster
Flashing or replacing the PCM

I hope the information in this article has been helpful in guiding you in the right direction to resolve the issue with your brake booster pressure sensor fault code. This article is strictly informational, and your vehicle’s specific technical data and service bulletins should always take precedence.

What does it mean?

This is a generic powertrain diagnostic trouble code (DTC) and applies to OBD-II vehicles equipped with a brake booster pressure sensor. This may include, but is not limited to, vehicles from Fiat, Alfa Romeo, Nissan, Ford, Dodge, Pontiac, Chevrolet, Acura, Subaru, Hyundai, etc. While generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

Fault code P0556 is one of several possible codes associated with the brake booster pressure sensor circuit.

This code indicates that the Powertrain Control Module (PCM) has detected a malfunction affecting the operation of the brake booster pressure sensor circuit. Common codes related to brake booster pressure sensor circuit malfunctions include P0555, P0556, P0557, P0558, and P0559. The specific situation determines which code is triggered by the PCM and whether the brake warning light illuminates or flashes during braking.

The purpose of the brake booster pressure sensor circuit is to monitor the amount of pressure (vacuum) applied to the brake booster. The circuit is controlled by the PCM to adapt to various braking conditions and adjust pressure to assist with brake pedal operation. This process is essential for power brakes to function correctly, allowing the vehicle to slow down or stop safely with minimal foot pressure applied to the brake pedal.

Code P0556 is set by the PCM when the brake booster pressure sensor circuit is out of range or not functioning properly.
How severe is this DTC?

The severity of this code varies depending on the specific malfunction and will escalate if not addressed promptly. At some point, the vehicle’s safety level could become compromised, requiring immediate attention.

Photo of a brake booster pressure (vacuum) sensor:

What are some symptoms of the code?

Symptoms of a P0556 error code may include:

Brake warning light flashing during braking
Brake warning light staying illuminated
Illuminated service engine soon light
Increased effort required to depress the brake pedal

What are some common causes of the code?

Causes

of this P0556 code may include:

Faulty brake booster pressure sensor
Worn or damaged vacuum lines
Corroded or damaged connector
Damaged or faulty wiring
Defective brake booster
Faulty PCM

What are the troubleshooting steps for P0556?

The first step in the troubleshooting process for any malfunction is to check technical service bulletins for known issues with the specific vehicle.

Locate all components associated with the brake booster pressure sensor circuit. This includes the brake booster pressure sensor, brake booster, vacuum lines, wiring, connectors, and the PCM in a simplex system. Once these components are located, perform a thorough visual inspection to check that all related wiring and connectors show no obvious defects such as scraping, rubbing, exposed wires, or burn marks. Connectors should also be examined for corrosion buildup or damaged pins. Vacuum lines should be inspected for security, weather cracking, leaks, and overall service condition.
Advanced Steps

Advanced steps become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and vehicle-specific technical references. Voltage requirements will be highly dependent on the specific year, make, and model of the vehicle.
Circuit Checks

Voltage requirements vary depending on the specific vehicle, brake booster pressure sensor circuit configuration, and integrated components. Technical data must be referenced for the correct voltage range for the brake booster pressure sensor and the appropriate troubleshooting sequence. Correct input voltage to a sensor with no output voltage typically indicates internal failure.

If this process identifies a missing power source or ground, continuity tests may be necessary to verify the condition of wiring and connectors. Continuity tests are always performed with power disconnected from the circuit, and normal readings should show 0 ohms resistance unless otherwise specified by technical data. Resistance or lack of continuity indicates faulty wiring or connectors that are shorted or open and need repair or replacement.
Common Repairs

Replacing a faulty brake booster pressure sensor
Cleaning corrosion from connectors
Repairing or replacing wiring
Replacing the brake booster
Flashing or replacing the PCM

I hope the information in this article has been helpful in guiding you in the right direction to resolve the issue with your brake booster pressure sensor fault code. This article is strictly informational, and technical data and service bulletins specific to your vehicle should always take precedence.

What does it mean?

This is a generic powertrain diagnostic trouble code (DTC) and applies to OBD-II vehicles equipped with a brake booster pressure sensor. This may include, but is not limited to, vehicles from Fiat, Alfa Romeo, Nissan, Ford, Dodge, Pontiac, Chevrolet, Acura, Subaru, Hyundai, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

Fault code P0557 is one of several possible codes associated with the brake booster pressure sensor circuit.

This code indicates that the Powertrain Control Module (PCM) has detected a malfunction affecting the operation of the brake booster pressure sensor circuit. Common codes related to brake booster pressure sensor circuit malfunctions include P0555, P0556, P0557, P0558, and P0559. The specific situation determines which code is triggered by the PCM and whether the brake warning light illuminates or flashes during braking.

The purpose of the brake booster pressure sensor circuit is to monitor the amount of pressure (vacuum) applied to the brake booster. The circuit is controlled by the PCM to adapt to various braking conditions and adjust pressure to assist brake pedal operation. This process is essential for power brakes to function correctly, allowing the vehicle to slow down or stop safely with minimal foot pressure applied to the brake pedal.

Code P0557 is set by the PCM when the brake booster pressure sensor circuit has a low output voltage.
How severe is this DTC?

The severity of this code varies depending on the specific malfunction and will escalate if not addressed promptly. At some point, vehicle safety could become compromised, requiring immediate attention.

Photo of a brake booster pressure (vacuum) sensor:

What are some symptoms of the code?

Symptoms of a P0557 fault code may include:

Brake warning light flashing during braking
Brake warning light staying illuminated
Service engine soon light illuminated
Increased effort required to depress the brake pedal

What are some common causes of the code?

Causes

of this P0557 code may include:

Faulty brake booster pressure sensor
Worn or damaged vacuum lines
Corroded or damaged connector
Damaged or faulty wiring
Defective brake booster
Faulty PCM

What are the troubleshooting steps for P0557?

The first step in troubleshooting any malfunction is to consult technical service bulletins for known issues with the specific vehicle.

Locate all components associated with the brake booster pressure sensor circuit. This includes the brake booster pressure sensor, brake booster, vacuum lines, wiring, connectors, and the PCM in a simplex system. Once these components are located, perform a thorough visual inspection to check for obvious defects such as chafing, rubbing, exposed wires, or burn marks. Connectors should also be inspected for corrosion buildup or damaged pins. Vacuum lines should be checked for security, weather cracking, leaks, and overall service condition.
Advanced steps

Advanced steps become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and vehicle-specific technical references. Voltage requirements will be highly dependent on the specific year, make, and model of the vehicle.
Circuit checks

Voltage requirements vary depending on the specific vehicle, brake booster pressure sensor circuit configuration, and integrated components. Technical data must be referenced for the correct voltage range for the brake booster pressure sensor and the appropriate troubleshooting sequence. Correct input voltage to a sensor with no output voltage typically indicates internal failure.

If this process identifies a missing power source or ground, continuity tests may be necessary to verify the condition of wiring and connectors. Continuity tests are always performed with the circuit power disconnected, and normal readings should show 0 ohms resistance unless otherwise specified by technical data. Resistance or lack of continuity indicates faulty wiring or connectors that are shorted or open and need repair or replacement.
Common repairs

Replacing a faulty brake booster pressure sensor
Cleaning corrosion from connectors
Repairing or replacing wiring
Replacing the brake booster
Flashing or replacing PCM

I hope the information in this article has been helpful in guiding you in the right direction to resolve the issue with your brake booster pressure sensor fault code. This article is strictly informational, and technical data and service bulletins specific to your vehicle should always take precedence.