A P0558 trouble code is related to a vehicle’s brake booster pressure sensor and its signal being sent to the engine computer.
What the P0558 code means
P0558 is an OBD-II generic code for a voltage problem with the brake booster pressure sensor in that the signal being sent to the engine computer during braking is too high for the manufacturer’s parameters. This will make the computer think pressure is too high, sometime resulting in a firm brake pedal.
What causes the P0558 code?
The most common causes for a P0558 are:
- Brake booster vacuum leaks
- Faulty brake booster pressure sensor
- Faulty wiring to the brake booster pressure sensor
- Low power steering fluid (if the brake booster is hydraulic)
What are the symptoms of the P0558 code?
Symptoms will vary from a simple check engine light, to a firm brake pedal that’s difficult to depress.
How does a mechanic diagnose the P0558 code?
Your mechanic will first visually inspect the brake booster, looking for any damaged wiring, hoses, electrical connectors, or low fluid levels. They will conduct a basic vacuum leak test of the hoses to determine if a simple hose replacement is in order. If anything seems out of place, parts will be replaced or repaired. However, if the visual inspection and vacuum leak test checks out, your mechanic will test the resistance of the brake booster pressure sensor before replacing it.
Common mistakes when diagnosing the P0558 code
Some P0558 codes can be caused by low fluid levels, 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.
How serious is the P0558 code?
Most P0558 codes won’t cause any serious issues other than a check engine light, but in some cases, hard brake pedals will result.
What repairs can fix the P0558 code?
The most common repairs for a P0558 are as follows:
Additional comments for consideration regarding the P0558 code
Some P0558 codes are intermittent and can be cleared without a return, so it’s wise to clear the code and reset the engine computer first before parts are replaced.
Need help with a P0558 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.
This article originally appeared on YourMechanic.com as P0558 OBD-II Trouble Code: Brake Booster Pressure Sensor Circuit High and was authored by Logan Utsman.