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Om651exhaust back pressure sensor p047128 jumps to 2 bar after shutting off engine . Fixed!

kingkhan

Member
Joined
Oct 28, 2021
Messages
55
Location
huddersfield
Car
e250 cdi estate
Problem: EML, late gear changes, jerking, no power. Realised my plug had unplugged itself from the sensor. But after refitting there was still a problem.

Ok so i fitted a new exhaust back pressure sensor (EBPS) but the engine is still throwing this fault p047128. If i drive it after clearing the fault the sensor readings are perfect and car is back to 100% but when the engine is turned off, after exactly 1minute the EBPS jumps to 2bar and the fault returns and car is back to limpmode. I have tried 3 sensors including original..all doing the same thing. All dpf readings and pressures are fine, car drives perfect until the car is turned off .

I Tried fo find info all over the net about this but no answers! It taken me many hours to fix this issue.

So just for your info, the sensor has a small pinhole which pushes air out into the plug (yea the plug connector! which also has vent hole). This then gives a reading. Also if it shows 2bar then unolug the sensor while car is running then plug back it and it will return pressure back to 1bar.

FIX: pull back the connector from sensor a tiny bit whilst its plugged in. do not push it down as far as it goes because there needs to be a gap between the 2 tiny holes (one on the sensor and one on the plug that measures the pressure reading). I used some silicone spray on the rubber watertight seal of the plug to make the plug side on easily otherwise it needs a tight push which ends up being pushed down too far. Best way to do it it push it until you feel a clip then pul back on the plug. If you have live data, turn the car off and watch it. If the pressure stays at about 1.01-1.1bar then your problem is sorted. If it jumps to 2.0bar you need to fiddle with the plug
 

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Update! The problem returned today ,same fault as above. I removed the plug and saw the small rubber seal that keeps the plug watertight. This makes it very hard to push the sensor on. So what was happening was the sensor plus was being pushed off too far back due to the rubber o ring not allowing it to push onto the sensor.
I removed the rubber seal from innder edge of the plug and problem solved! The plug has Much better, easy fit now and reading fine! See picture20241222_235306.jpg
 

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