Hi All,
I wanted to share this free fix I just performed on my 2006 M3. I scoured this forum and others for hours and found this tip on another UK forum for e46 cars that I tried and it works! Symptom is you get the simlutaneous yellow DSC and BRAKE lights on the dash and a beep, and when you read the codes you will see error 5E20 (pressure sensor 1) or 5E21 (pressure sensor 2) or both. Mine began years ago with 5E21 coming up intermittantly, then recently became both #1 and #2 faulty all the time. Because I rarely drive the car and it was in storage for a couple years, the matter wasn't pressing and the sensors are a major PITA to change and not cheap at $180ea from BMW (other brands are junk).
Apparently this fault is not always caused by a "bad" sensor, but pretty much everyone online says to just replace the "bad" one. It can also be caused by dirty fluid gunking up the valve in the sensor, or in my case the car sitting so long, even with clean fluid, that the valve gets stuck out of position inside the sensor body. OK, here is the fix. Look carefully down below the master cylinder with a bright light and you will see the 2 sensors screwed into the body of the MC. They are brass. The one closest to the firewall is #1, the one furthest to the front bumper is #2. Get a small hammer and a long enough punch to reach the sensor bodies (I used a brass one to not mar the finish of the sensors) or if you dont have that then a large flat screwdriver should work. Tap the sensor body a few times, lightly, in different areas.
I connected my Foxwell reader tool that allowed me to monitor the reading of each sensor real time. I could quickly see the sensor reset from about +40 to +70 and barely moving when pressing the pedal, to the correct negative values -9 and -13 once I tapped a few times to loosen the valves inside. When you press the brake pedal after clearing, assuming normal operation, you will see the values go from slightly negative and a linear gain to about 900 on a hard press with car running (or 300-400 without car on), and both #1 and #2 should have similar readings if working correctly. Also, the dash lights went off right away once I did this, no need to clear codes or reset anything. Of course if the problem reoccurs then you will need to replace the sensor(s), but the poster I saw said his car had been fine ever since after doing this. Good luck!
I wanted to share this free fix I just performed on my 2006 M3. I scoured this forum and others for hours and found this tip on another UK forum for e46 cars that I tried and it works! Symptom is you get the simlutaneous yellow DSC and BRAKE lights on the dash and a beep, and when you read the codes you will see error 5E20 (pressure sensor 1) or 5E21 (pressure sensor 2) or both. Mine began years ago with 5E21 coming up intermittantly, then recently became both #1 and #2 faulty all the time. Because I rarely drive the car and it was in storage for a couple years, the matter wasn't pressing and the sensors are a major PITA to change and not cheap at $180ea from BMW (other brands are junk).
Apparently this fault is not always caused by a "bad" sensor, but pretty much everyone online says to just replace the "bad" one. It can also be caused by dirty fluid gunking up the valve in the sensor, or in my case the car sitting so long, even with clean fluid, that the valve gets stuck out of position inside the sensor body. OK, here is the fix. Look carefully down below the master cylinder with a bright light and you will see the 2 sensors screwed into the body of the MC. They are brass. The one closest to the firewall is #1, the one furthest to the front bumper is #2. Get a small hammer and a long enough punch to reach the sensor bodies (I used a brass one to not mar the finish of the sensors) or if you dont have that then a large flat screwdriver should work. Tap the sensor body a few times, lightly, in different areas.
I connected my Foxwell reader tool that allowed me to monitor the reading of each sensor real time. I could quickly see the sensor reset from about +40 to +70 and barely moving when pressing the pedal, to the correct negative values -9 and -13 once I tapped a few times to loosen the valves inside. When you press the brake pedal after clearing, assuming normal operation, you will see the values go from slightly negative and a linear gain to about 900 on a hard press with car running (or 300-400 without car on), and both #1 and #2 should have similar readings if working correctly. Also, the dash lights went off right away once I did this, no need to clear codes or reset anything. Of course if the problem reoccurs then you will need to replace the sensor(s), but the poster I saw said his car had been fine ever since after doing this. Good luck!
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