Sylphy brake booster pressure sensor error

That's definitely concerning, especially the poor braking effect. The brake booster pressure sensor error does point to a potential issue with the ABS system. Could be a faulty sensor, or as you suspect, related to the incorrect bleeding. Have you checked the ABS system module for any physical damage or corrosion? Also, what diagnostic tool are you using? Some generic readers might not give you the full picture.

Good point about the ABS module. I'll give that a look tomorrow when it's light out. As for the tool, it's a mid-range one, specifically a Foxwell NT510 Elite. I can usually pull pretty detailed codes with it. Do you think a failing ABS pump could cause this, even if the code specifically mentions the pressure sensor?

While a failing ABS pump could theoretically contribute to braking issues, the specific error code pointing to the pressure sensor is pretty telling. Given you had the system bled incorrectly previously, it's plausible air got trapped, affecting the sensor's readings. I'd still check the ABS module for damage, but honestly, based on your description, it sounds like a trip to a reputable workshop might be the best bet. They can perform a proper diagnostic and potentially replace the sensor. Vehicle safety is paramount.

Thanks for the insights! I checked the ABS module, didn't see any obvious damage. I took it to my trusted mechanic. Turns out you were right, it was indeed the brake booster pressure sensor! They replaced it, re-bled the brakes, and all is well. The part plus labor came to 90€ Appreciate the help!