I just completed a leak down test and checked what the air pressure regulator gauge showed versus the quad recon gauge. The recon showed 6 psi less pressure than the regulator showed. So I proceeded to check the MAP sensor voltage and wire harness voltage. The wire harness had 5 volts which I take it is the norm for the 99 model year. The Sensor it self read .54 volts on a digital meter and slightly less then .5 volts (.5 volts reference at 1 atmosphere) on my analog volt meter. My question now is: is it worth it to replace the MAP sensor? Does a few hundredth of a volt off going to throw the reading off by 6 psi? (not sure if it matters but I'm about 2,500 ft above sea level) Or is my recon reading the signal wrong?

On a 2nd note, after I unplugged the MAP sensor it set off the check engine light as expected but I have tried many times to complete the code check thing (on, off, on, off, on) but couldn't get it to work. I can get the gauge check function to work but no matter what I try I can't get the truck to show the codes. Can anyone break this down into baby steps so I try and figure out what the heck I'm doing wrong??

Again, thanks everyone for all the help!

Brad

 

I believe you should be good at .54 (.3 or less would be too low).

I'm not sure that you can get the codes to show up in the odometer in a 99. I know I can't in my 98.5.

 

Some 2001 and up show the codes I believe. Mine does it's a 2001. Key on, off, on, off, on, and codes read out on the odometer.

 

So if the voltage is showing good on the MAP then why the 6 psi difference between the recon and the regulator???

Ok, cool then I'm not a tard and the 99's just don't have that feature.

Thanks for the help guys!

 

every guage has its tolerences maybe between the 2 and the wiring and everything it comes out 6psi different