Testing a MAPP sensor?

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dvo - 19 Jul 2007 00:11 GMT

Found out what the vacuum sensor assembly was, just a MAPP sensor. Does
not give an failure code on the ECM. Book explains how to test, but want
to make sure the values for the test are acurate. Initial test shows 3.5V
and with 25 inHG it gives a reading of 1.5V. The manual indicates it should
be approximately 0.5V. What does approximately mean and is 1.5V close
enough or is that an indicator of MAPP sensor failure. Can't find spare
parts at salvage yards to compare and the new one that I ordered is quite
expensive ($250 U.S.). It would be nice to find out it someone is an
expert on this sensor to make sure it is bad.

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qslim - 19 Jul 2007 03:06 GMT

Considering that the circuit works on a range of 0 to 5 volts, I would
consider a 1v discrepancy to be well out of range, so I'd call it a bad
sensor. I trust you're using a vacuum gauge and a meter?

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johngdole@hotmail.com - 21 Jul 2007 06:21 GMT

The Autozone's free online guide shows 19.69 in/Hg will result in
about 2v drop. So 5V input - 2V drop = 3V reading.

But 25 in/HG is way off the charts. Tray again with 4-19 in/HG of
vacuum and compare to the AutoZone chart:

http://www.autozone.com/az/cds/en_us/0900823d/80/13/ec/cc/0900823d8013eccc/repai
rInfoPages.htm

BTW, the good old 3SFE kinda sucks. But I don't know any 3SFE can
literally suck 25 in/HG vacuum. So check your manual again.

> Found out what the vacuum sensor assembly was, just a MAPP sensor. Does
> not give an failure code on the ECM. Book explains how to test, but want
[quoted text clipped - 5 lines]
> expensive ($250 U.S.). It would be nice to find out it someone is an
> expert on this sensor to make sure it is bad.

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