MAP sensor

[acazin at interlog.com]

> Now, the frequency output of the OEM unit -- seems that
> that would entail either an F-V convertor and then A-D or an
> interrupt driven timer circuit that would return a number of counts
> proportional to the period of the sensor output.  Any suggestions?


Expect the Ford MAP to be a few $ more than a GM or Chrysler MAP. But 
the digital output means that it can be processed by the 
microprocessor directly, without A-D conversion.

So, if your control module can accept the signal, this signal is 
ready for consumption.

You could probably buy the sensor from a junk yard (I don't recommend 
it), to save a few $, but if you do, check it for proper operation.

Use a hand held vacuum pump, give it 5V and ground, and measure the 
frequency output (on the center wire of the connector) from 0 in. to 
25 in. of vacuum, in 5 in. vacuum intervals (ie. 0, 5, 10, 15, 20 
, 25).  Then, graph the freq. vs. vacuum and you should get a 
straight line (a little drifting is OK.)

Also, tap on the sensor and maybe heat it to see if "it gets lost". 
If it passes these simple tests, then the sensor is OK.

Alex Cazin