Citroen SM MAP sensor 0280100036 not working

Hi Rhys,

interesting subject though. I have followed here what Bosch and others like PB Anders have proclaimed and I saw the electrical circuit that causes the overlay and prioritization with the potentiometer. So it seemed to confirm what has been proclimed for so long. However, I will do a test these days where I will do an experiment. How far does a broken MAP sensor influence idle-run CO setting via potentiometer. You made me curious.

So far the cases I had in my hands where idle-run CO would not fit were either broken ECUs or mostly false air in intake manifold. Now a completely broken diaphragm in a MAP sensor would of course also be a source of false air. But it will be intersting to see, how far a mistuned of completely false sensor can effect idle-run CO.

I will let you know.

Hi Volker,

While I do not understand the MAP sensor theory in the detail that you and some others do - I appreciate the concept of the relationship between MAP sensor and ECU.

My colleague describes how over 20 years at a Volvo-only workshop (at a time when D-jet 140, 164 & P1800-s were common) that it was typical that when they uncovered defective MAP sensors - that those vehicles allowed simultaneous mixture adjustment at both ECU and MAP sensor at idle. Defective cars were returned to the road where that car & service client were maintained satisfactorily for many years. He has a recollection of 20+ exact scenarios like this. I unreservedly believe his word and his real-life experience trumps ......my readings.

So, it would seem sensible to send my MAP sensor to Bosch for repair & verification. I have some document (here somewhere) that explains the Bosch procedure to do this. I feel like I aught remove the epoxy potting covering the adjuster and do some CO tests first (is the epoxy "factory sealed" or has someone re-filled it with araldite after some tampering years ago?)

Cheers,
Rhys

Hi Volker,

I removed the potting from the end of my MAP sensor. It is difficult to see through the aperture, but there are some signs of irregular marks within the unit.

The potting on the end of the sensor looks neat - and I presumed factory. Do you thinks this is the case?

Regards,
Rhys

Hi Rhys,

well that is hard to say from a picture. Original potting is of a dark yellow and it is half transparent. You can see the screw underneath through it. It seems that Bosch used a ring which they set on the MAP sensor to fill it. the potting does not contain air bubbles and it is not straight but slightly convex.

Hi Rhys,
it looks like this one isn't originally sealed to me.
The bubbles inside, the height - two indicators for this,

One wanted to create a 'looks like originally sealed' look.

Have a look at the rivets, too. There should be a stamp (three digits) on one of the heads showing the year and month of production.
Missing stamp would mean it has been opend before, in my opinion.

Regards
Norbert

That is how a 0 280 100 048 looks like in new. Looks different than yours.