selina_weiss82
Matrix Brake Booster Pressure Sensor Fault
Summary of the thread
The main issue discussed is a brake error and poor braking power in a 2004 Hyundai Matrix diesel, attributed to a faulty brake booster pressure sensor. The problem likely arose from air entering the brake system during a self-conducted brake bleed, potentially due to the master cylinder running low on fluid. This air can cause incorrect sensor readings and may damage the sensor over time. The recommended solution is to have a professional re-bleed the brakes and diagnose the sensor, which ultimately led to the sensor being replaced and the brakes properly bled at a workshop.
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4 comment(s)
selina_weiss82 (community.author)
I thought I followed the bleeding sequence correctly, starting with the wheel furthest from the master cylinder, and so on. But keeping the master cylinder topped up? I might have let it drop a little too low a couple of times. Could that REALLY be the culprit? And if so, is the sensor actually broken, or just giving a false reading because of the air?
reinhardsky71
Letting the master cylinder run dry during bleeding is a classic mistake, and yep, it can absolutely cause these issues! It introduces air into the ABS module, which is a pain to get out. As for whether the sensor is truly bad or just misreading, it's tough to say without more diagnostics. The sensor itself might be fine, but the air in the system is giving it a false reading. However, repeated false readings can damage sensitive electronic components over time. I would recommend taking it to a workshop and letting a professional sort it out. They have the tools and know-how to properly bleed the ABS and diagnose the sensor.
selina_weiss82 (community.author)
Thanks a million for the advice! I suspected I might have messed up that brake bleeding. I took it to the shop. Turns out, air in the system was indeed the main problem, but the pressure sensor was also damaged, maybe because of the bleeding. They replaced the sensor and re-bled the brakes correctly, costing me 90€. Lesson learned: I'm sticking to oil changes from now on!
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HYUNDAI
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MATRIX
reinhardsky71
Sounds like you've got a serious issue! A faulty brake booster pressure sensor definitely explains the error message and poor braking. If air gets trapped in the system, especially near the ABS module or brake booster, it can cause all sorts of weird problems. Air is compressible, unlike brake fluid, so it will affect the efficiency of the hydraulic brake system and in turn the sensor readings. Did you follow the proper bleeding sequence for your Matrix, and did you make sure to keep the master cylinder topped up?