P0558 OBD Error Code: Problem & Solutions

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OBD-II Code Powertrain Control Module (PCM) failure is defined as a Brake Booster Pressure Sensor Circuit High. This is a generic powertrain diagnostic trouble code (DTC) and applies to OBD-II vehicles that have a brake booster pressure sensor. Trouble code P0558 is one of several possible codes associated to the Brake Booster Pressure Sensor Circuit. It indicates that PCM has detected a fault in the brake booster pressure sensor circuit.

P0558 is a diagnostic trouble code (DTC) and technically described as "Brake Booster Pressure Sensor Circuit High". Code P0558 is set by the PCM when the brake booster pressure sensor circuit has a higher than expected voltage reading. The purpose of the brake booster pressure sensor circuit is to monitor the amount of pressure (vacuum) applied to the power brake booster. The circuit is controlled by the PCM to adapt various braking situations and adjust the pressure to assist brake pedal operation. 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. If the engine computer discovers doubtful signal from the Brake Booster Pressure Sensor, code P0558 will be set.

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

• Inoperative brake booster
• Faulty brake booster pressure sensor
• Damaged Vacuum lines
• Damaged, broken or corroded wiring and connector
• Poor electrical connection
• Faulty 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 - Brake pedal is the pedal used by the driver of a vehicle to operate the brakes. It should depress easily else repair or replace as required.
3. Brake Wiring and Connector - Inspect the brake wiring and connector carefully and replace the damaged, corroded or broken immediately.
4. Vacuum Lines - A vacuum line or hose, which can also be referred to as a “line” or a “tube,” is a flexible rubber connection that routes manifold vacuum to various components and accessories. Replace the leaked ones immediately.
5. ECM/PCM - The Engine Control Module (ECM) provides the brains for the engine of the vehicle. In addition to controlling the fuel mixture, the ECM also makes sure the timing and emissions control system work properly, as well as a variety of other systems and sensors.

Below are the common symptoms for the code P0558. If you experience below mentioned symptoms please bring your vehicle to a reputable repair facility. Keep in mind; problems don’t get better over time unless rectified.

• Hard Brake Pedal
• Increased effort required to depress brake pedal
• Flashing of check brake light while braking
• Illuminated check engine light

The most common problem you may confront due to this code is hard brake pedal which actually requires increased efforts or pressure to compress the brake pedal. However, you might not face any other drivability issue but hard pedal could itself lead to the accident. It’s better to address this code immediately to avoid any such condition.

• Replace the faulty brake booster pressure sensor.
• Inspect the brake booster carefully and replace if you discover it frayed or inoperative.
• Check out the corresponding wiring and related connector, repair or replace the damaged, broken or corroded one.
• Faulty ECM/PCM should be diagnosed thoroughly and do the necessary repairs.

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To diagnose this code, one should seek assistance from a trained automotive diagnostician but if you want to do it by yourself, please follow the below mentioned steps:

• Begin with a visual inspection of all wiring and connectors.
• Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary.
• Continue by clearing the code and operating the vehicle to see if it returns.
• Proceed with your diagnosis with a visual inspection of the brake booster system.
• Make sure that there is no fluid leaking from the rear of the master cylinder into vacuum booster.
• Inspect all vacuum supply hoses used to supply the vacuum brake booster.
• If the system uses a hydraulic booster, visually inspect the power steering pump, lines, fluid condition, and fluid level.
• Also take a look at the 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 vacuum source checks out 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 brake booster 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 coincide.
• 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 or vacuum gauge.
• Consult your vehicle’s service manual and compare your findings, replace or repair power steering system or vacuum supply/engine components as needed.

Common Mistakes When Diagnosing the P0558 Code

Low fluid levels could also be one of the causes storing this trouble code P0558, especially if the vehicle in question uses a hydraulic brake booster feed by the power steering pump. Overlooking this may not cause the code to go away.