Guide To P0559 OBD Error Code Solutions

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Error Code P0559 is defined as Brake Booster Pressure Sensor Circuit Intermittent. This means there is a problem with the brake booster pressure sensor, likely caused by vacuum leaks or other problems with the brake booster sensor itself. This code is one of the many possible codes associated with the brake booster pressure sensor circuit. When this appears, it means the PCM has determined an error indicating that the brake booster pressure sensor circuit is out of range, or not running properly due to abnormal feedback.

OBD-II Code Powertrain Control Module (PCM) failure is defined as a Brake Booster Pressure Sensor Circuit Intermittent. The job of the brake booster pressure sensor circuit is to monitor the amount of pressure (vacuum) applied to the power brake booster. This process is controlled by the PCM to allow the vehicle to adapt to various braking situations and adjust the pressure needed by the vehicle to assist the operation of the brake pedal. This process is crucial for the power brakes to work efficiently and safely and safely slow down or stop the vehicle with minimum amount of foot pressure being applied to the vehicle. This code is set by the PCM when the brake booster pressure sensor circuit has an intermittent output voltage signal problem.

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

• Vacuum leaks in vacuum brake booster
• Faulty brake booster pressure sensor
• Damaged booster vacuum hoses
• Corroded, damaged, or loose electrical components or circuits
• Low level of power steering fluid
• Inoperative steering pump (leads to failure of hydraulic brake)
• Frayed brake booster (in rare cases)

1. Brake Booster - The brake booster improves braking performance and safety by reducing the pedal pressure. Replace or repair the faulty one to avoid any major issue.
2. Brake Connector - Check out the brake connector on regular basis as the corroded or broken connector could also be the cause for storing this code.
3. Brake Pedal - If you face any difficulty while compressing the brake pedal then kindly repair or replace it as it could lead to the accidents as well.
4. Vacuum Hose - Leaked vacuum hoses or lines can create major issues in no time so always repair or replace the leaked vacuum hoses immediately.
5. ECM/PCM - The Engine Control Module (also called the Powertrain Control Module or PCM) is the brains of the engine management system. It controls the fuel mixture, ignition timing, variable cam timing and emissions control.

This issue should not be unattended as it could develop into something much more serious fairly quickly. Below are the common symptoms for the code P0559. If you experience these please bring your vehicle to a reputable repair facility.

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

To correct or fix this code one should seek assistance from a trained automotive diagnostician but if you want to do it by yourself, please do the below mentioned repairs and replacements to fix this code:

• Replacement of brake booster pressure sensor
• Repair or replacement of faulty electrical components in the brake booster (connectors and wires)
• Replacement of leaking vacuum hoses
• Replacement of damaged hoses and valves in brake booster system
• Replacement of brake booster

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It is always advised that TSB (Technical Service Bulletin) should be referred when troubleshooting this code. Some common steps to diagnose this code are as follows:

• 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 P0559 Code

As the description of this code suggests that this code is related to the brake booster pressure sensor so believing that the faulty sensor is the main cause responsible for storing this code is the biggest mistake usually people do while diagnosing this code and they replace the sensor instead of doing a thorough diagnosis.