Skip the auto shop - Our mechanics make house calls

P0557 OBD-II Trouble Code: Brake Booster Pressure Sensor Circuit Low

diagnostic check engine light

P0557 code definition

The P0577 vehicle trouble code indicates an issue with the brake booster pressure sensor circuit.

What the P0557 code means

The P0577 code identifies a pressure problem within the brake booster. When the brake booster pressure sensor fails to send a voltage input signal to the PCM that is satisfactory (or proportionate to the vehicle velocity required) the P0557 code will be stored. This usually indicates that the brakes were applied and the pressure within the brake system was not sufficiently to factory specifications.

Some vehicles will require multiple ignition cycles in which this problem occurs to trigger the check engine indicator light, but the P0557 code will still be stored, sometimes as a “pending code” if the issue is only an initial failure.

What causes the P0557 code?

The P0557 code has a number of common causes:

  • An issue with the brake booster pressure sensor
  • Vacuum leaks into the vacuum brake booster
  • Defective or broken vacuum hoses
  • Defective or broken electrical circuitry

If your vehicle’s brake boosters are hydraulic:

What are the symptoms of the P0557 code?

When the P0557 code appears, it is usually accompanied by the Check Engine light illuminating on the vehicle’s dashboard. Depending on the source of the problem, physical symptoms of a brake issue may be present before the Check Engine light illuminates. The brake pedal may be unresponsive or softer than usual. Brake performance may be affected. In some cases, brake performance is not affected but the feel of the brake pedal is still noticeably softer. It may take multiple presses of the brake pedal to cause the OBD-II system to store the P0557 code.

How does a mechanic diagnose the P0557 code?

A qualified technician with an OBD-II code scanner capable of retrieving factory readings from the vehicle. The technician will view the trouble code and see the time that it was stored. After that has been observed, the codes will be cleared before the vehicle is taken for a test drive. If, during the course of the drive, the code appears again, then it will be confirmed that the problem is indeed related to the P0557 code and not an intermittent issue that may be caused by electrical malfunctions.

Once the P0557 code is confirmed as the source of the problem, then the diagnosis can move onto the next step. The technician will use a voltmeter to test the circuits around the brake booster pressure sensor and the powertrain control module. A visual inspection of the wires and connections will then take place. After that, the inspection will move onto the brake booster itself and all of the vacuum lines surrounding it.

Common mistakes when diagnosing the P0557 code

While a malfunctioning brake booster will cause the P0557 code to appear, the code can also be caused by an electrical malfunction or a leaking vacuum line. In applications that use a hydraulic brake booster, leaking hydraulic fluid lines and leaky connections can cause the P0557 code to appear. The sensor responsible for monitoring pressure within the brake booster is prone to malfunctioning as well. If this sensor cannot properly read and relay that data, the P0557 code will appear.

How serious is the P0557 code?

The P0557 code is serious enough to warrant getting a professional to diagnose the problem as soon as the code appears. A problem with the brakes is inherently hazardous, and declining brake performance is dangerously unpredictable. The code itself will not prevent the engine from starting, but that does not mean that the vehicle is safe to drive when the brake booster does not have proper pressure.

What repairs can fix the P0557 code?

The most common repairs to address the P0557 code are as follows:

Additional comments for consideration regarding 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.

Need help with a P0557 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0121 OBD-II Trouble Code: TPS "A" Circuit Range Performance Problem
P0121 code definition Throttle Pedal Position Sensor/Switch (TPS) A Circuit Range Performance Problem What the P0121 code means P0121 is a generic OBD-II code which indicates that the Engine Control...
How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...


Related questions

Q: Jeep is throwing code p0441 and code 13. Checked front hoses. OK. Evap leak? Any help?

Hi - the P0441 code indicates that there is no flow of fumes detected from the gas tank/evap cannister to the engine. This could be caused by a faulty leak detection pump in the gas tank, failed purge valve, bad...

Q: Do all cars have an OBD system?

Virtually all vehicles from the 1987 model year to the present day have an OBD system. Some earlier model year vehicles, but not all, have some semblance of an OBD system. However, their diagnostic abilities are severely limited. There are...

Q: eva PO597 engined coolant thermostat heater control circuit from obd diagnostic tool

Hi there. For the code P0597 to appear, there is an issue with the engine cooling system. Check the harness to the thermostat housing and a good connection and make sure that there is corrosion. Check for any coolant leaks...