Field Service Mode

[David Mulvey]

My 87 IROC 5.0 has a ping problem when I get on it hard. Error codes light up indicating a bad MAF or MAF relays or wires inbetween.  
I tested and cleaned and check all componants best I know how.  Everything seemed OK.  MAF gives a voltage of .7 Volts at idle, and 
when I gas it in the driveway it jumps to about 2 Volts. It's got a new block.

One thing that I don't understand is why does my car run perfect with no pinging with the ECM in Field Service Mode (Pins A and B 
shorted)?  Should I leave it in Field Service Mode?  Does the computer take sensors out of line in this mode and then somehow keeps 
the car running through a backup mode???

I am currently working on a diagnostic hookup so that I can fit right in on this list, hopefully that too will help out. I will be 
sure to post on my web site any software that I may develope.  Thinking of realtime window based displays of what ever word I would 
like to look at.  I have been doing this sort of thing at work on Military Aircraft, but this will be my own time, equipment, and 
serial based instead of 1553 bus.

Thanks

David
Lancaster, CA