Error Code P0557: What It Means & What To Do?

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If you are confronting a problem of hard pedal, illuminated check brake light and flashing of brake light while braking does not ignore it as these are the symptoms of diagnostic trouble code P0557 and related trouble codes. This code is an indication that the Powertrain Control Module (PCM) has detected a malfunction that is hindering the operation of the brake booster pressure sensor circuit. If the PCM fails to receive a voltage input signal from the brake booster pressure sensor that is proportionate to the decrease in vehicle speed required, a code will be stored and a malfunction indicator lamp will be illuminated.

OBD-II Code Powertrain Control Module (PCM) failure is defined as a Brake Booster Pressure Sensor Circuit Low. This usually indicates that the brakes were applied and the pressure within the brake system was not sufficient to factory specifications. The Brake Booster uses vacuum to make the brake pedal easier to depress when braking. The Brake Booster Pressure Sensor measures the amount of vacuum inside the brake booster. This process is essential for the power brakes to function properly and safely slow down or stop the vehicle with the minimum amount of foot pressure being applied to the brake pedal.

Code P0557 is set by the PCM when the brake booster pressure sensor circuit has low output voltage.

What causes this problem with the Brake Booster Pressure Sensor Circuit Low?

• Leaked or damaged vacuum lines
• Faulty brake booster pressure sensor
• Broken, lose or corroded brake connector
• Poor electrical connection or frayed wiring
• Inoperative brake booster
• Faulty ECM/PCM

1. Brake Booster - A brake booster is an enhanced master cylinder setup used to reduce the amount of pedal pressure needed for braking. Replace the faulty one to avoid related error codes.
2. Brake Pedal - If you want your vehicle to run smoothly the brake pedal of your vehicle should be smooth, it should compress easily else repair or replace it avoid any kind of accident.
3. Brake Connector - Brake connectors should not be loose, broken or corroded else can create major issues.
4. Brake Light - Brake light is a red light attached to the rear of a motor vehicle that lights up when the brakes are applied, serving as a warning to following drivers. It should not be malfunctioned.
5. Vacuum Lines - In order to avoid this and related codes vacuum lines or hoses should not be leaked or damaged else replace or repair it immediately.
6. ECM/PCM - A car's engine control module (ECM) is a computer system that acts as the "brain" of a car. This little computer analyses lots of information in order to control the car's performance. When the ECM fails, it will greatly hurt the engine's performance.

To identify any trouble code, one should be aware of the symptoms of that code. Below mentioned are some common symptoms for trouble code P0557 which can help you to identify this code.

• Flashing of check brake light while braking
• Increased pressure required while compressing brake pedal
• Illuminated check brake light
• Illuminated check engine light

This code has to be addressed immediately as it’s not safe to drive when the brake booster does not have proper pressure. Moreover, declining brake performance is dangerously unpredictable. Following repairs and replacements can help you to fix this code:

• Replace the faulty brake booster.
• Replace the frayed brake booster pressure sensor.
• Inspect the vacuum lines carefully and repair or replace the faulty ones as needed.
• Repair or replace the faulty wiring and connectors.
• Repair or replace the faulty ECM/PCM.

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The P0557 code is serious enough to warrant getting a professional to diagnose the problem as soon as the code appears. Steps to diagnose this trouble code are as follows:

• Locate all of the components associated with the Brake Booster Pressure Sensor Circuit.
• Check all of the associated wiring and connectors for obvious defects such as scraping, rubbing, bare wires or burn spots.
• The connectors should also be examined for corrosion build up or damaged pins.
• Vacuum lines should be inspected for security, weather cracks, leaks and the overall serviceability level.
• With the help of digital multimeter and the specific technical references check the voltage requirements of your vehicle.
• Voltage requirements will vary based on the specific vehicle, the Brake Booster Pressure Sensor Circuit configuration and the components incorporated.
• The correct voltage input to a sensor with no output voltage is normally an indication of internal failure.
• If this process identifies the absence of a power source or ground, continuity testing may be needed to check the condition of the wiring and connectors.
• Resistance or no continuity is an indication of faulty wiring or connectors that are shorted or open and must be repaired or replaced.

Common Mistakes When Diagnosing the P0557 Code

Do not replace parts such as the brake booster prior to having the P0557 code diagnosed by a qualified technician. Often the problem is rooted in an electrical malfunction or a leaking vacuum line within the brake system.