Description of the P0556 fault code.
OBD2 Error Codes

P0556 Brake Booster Pressure Sensor Range/Performance

26.05.2022 /

P0556 – OBD-II Trouble Code Technical Description

The P0556 code indicates that the PCM has detected a problem with the brake booster pressure sensor.

What does the fault code mean P0556?

Trouble code P0556 indicates a problem with the brake booster pressure sensor. This means that the engine control module (PCM) has detected an abnormal voltage input signal from this sensor when the vehicle is braking. In most cases, this error occurs when you press the brake pedal. It should be noted that on some vehicles the Check Engine light does not come on immediately, but only after detecting the error multiple times.

Fault code P0556.

Possible reasons

Some possible reasons for the P0555 trouble code:

  • Defective Pressure Sensor: A loose connection, damage, or failure of the brake booster pressure sensor can cause P0555 to appear.
  • Wiring or Connectors: Problems with the wiring or connectors connecting the pressure sensor to the PCM can cause incorrect data transmission and cause this error code to appear.
  • Low Brake Fluid Level: Insufficient brake fluid level in the power steering system can cause trouble code P0555.
  • Malfunctioning PCM: In rare cases, the problem may be due to a problem with the engine control module (PCM) itself, which is unable to properly process the signals from the pressure sensor.

What are the symptoms of a fault code? P0556?

When trouble code P0556 occurs, you may typically experience the following symptoms:

  • Check Engine Light: When trouble code P0556 appears, the Check Engine light may come on on your instrument panel. It alerts the driver that there is a problem in the brake booster system.
  • Increased braking force: Pressing the brake pedal may require more force than usual to stop the vehicle. This may be due to insufficient pressure in the brake booster system due to problems with the pressure sensor.
  • Instability of the braking system: If the brake booster pressure sensor malfunctions, the brake system may become unstable, which may make driving difficult.

How to diagnose a fault code P0556?

The following steps are recommended to diagnose DTC P0556:

  1. Checking the error code: Use an OBD-II scanner to read the P0556 error code and any other related codes.
  2. Visual inspection: Inspect the wires, connections, and connectors associated with the brake booster pressure sensor for damage, corrosion, or breaks.
  3. Pressure sensor test: Check the pressure sensor itself for correct connection and damage. Check that the pressure sensor is functioning properly.
  4. Chain test: Use a multimeter to check the voltage on the wires associated with the brake booster pressure sensor. Make sure the voltage meets the manufacturer's specifications.
  5. Checking vacuum hoses: Check the condition and integrity of the vacuum hoses associated with the brake booster system. Make sure they are not clogged or damaged.
  6. Check PCM: If all previous steps do not resolve the problem, you may need to check the PCM for defects or malfunctions. Refer to the technical documentation or service manual for your specific vehicle to complete this procedure.

After completing the above steps and fixing the problem, you need to clear the error code and take it for a test drive to ensure that the problem no longer occurs. If the problem persists, additional service or component replacement may be required.

Diagnostic errors

When diagnosing DTC P0556, the following errors may occur:

  • Lack of attention to detail: Some diagnosticians may skip a visual inspection of the brake booster system wires, connectors, and pressure sensor, which may result in missing the root cause of the problem.
  • Incorrect interpretation of scanner data: Some diagnostic scanners may provide incorrect or confusing data, making an accurate diagnosis difficult.
  • Incorrect voltage check: Incorrectly checking the voltage on the leads or reading the multimeter incorrectly can lead to incorrect interpretation of the results.
  • PCM malfunctions: In rare cases, the problem may be due to a malfunction of the PCM itself, but this is usually the final diagnostic hypothesis after careful examination of other components.
  • Incomplete resolution of the problem: If the cause of the problem has not been completely resolved, the error may reappear after clearing the error code.

To successfully diagnose and resolve the P0556 trouble code, it is important to pay attention to detail, use the correct equipment, and follow the repair manual for your specific vehicle model.

How serious is the fault code? P0556?

Trouble code P0556, indicating a problem with the brake booster pressure sensor, is quite serious as it can cause the brake booster system to not function properly. If the brake booster system is not functioning properly, the vehicle's braking performance and safety may be affected.

Improper operation of the brake booster may result in extended braking distances or difficult vehicle control in emergency situations. Therefore, the driver should immediately contact a service center to diagnose and repair the problem when the P0556 trouble code appears to ensure safe driving and prevent further damage or breakdown to the vehicle.

What repair will help eliminate the code? P0556?

The following repairs may be required to resolve DTC P0556:

  1. Pressure Sensor Replacement: If the pressure sensor is faulty or damaged, it should be replaced with a new one that meets the vehicle manufacturer's specifications.
  2. Checking and replacing electrical connections: Sometimes the error may be caused by a poor electrical connection between the pressure sensor and the PCM. Check the condition of the connections and, if necessary, clean them or replace damaged wires.
  3. Diagnosis of Other Components: Since the problem may be related not only to the pressure sensor, but also to other components of the brake booster system, such as wires, valves, or the brake booster itself, it is recommended to conduct a complete diagnosis of the brake booster system to identify all potential problems.
  4. PCM Software Update: In rare cases, the problem may be related to the PCM software. In this case, it may be necessary to update or reprogram the PCM followed by re-checking.

It is recommended that you contact a qualified automotive mechanic or service center for diagnosis and repair as correcting the problem may require specialized equipment and knowledge.

How to Diagnose and Fix P0556 Engine Code - OBD II Trouble Code Explain

P0556 – Brand-specific information

Trouble code P0556, related to the brake booster pressure sensor, can apply to various makes of vehicles, some of them are:

This is just a small list of brands to which this fault code may apply. For more accurate information about malfunctions and repair methods, you should contact the service manual or an authorized service center for each specific manufacturer.

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