My AEM 3.5 bar MAP sensor reads 1.59v (-1.1 psi) with the car off. I've tried two of these sensors and they give the exact same voltage at atmospheric.

Can anyone shed any light on this? BTW, I'm at sea level.

Thanks.

 

Should read around 1.7 volts with ign ON but car off. Check the grounds, and then measure the voltage at the Map sensor pin under the hood, and then again at the EMS pin to see if there is a difference. There could be some elec issues going on. Also verify its getting a full 5V to the map sensor power pin.

[ EDIT: 1.7v is for the 3.5bar sensor ... ]

 

Remember this is going to depend on where you live as well due to a map sensor reading true atmospheric pressure. It sounds about right but you will notice that the AEM sensors are a linear voltage so in some cases they may not read spot on compaired to your true atmospheric pressure but they are consistant so the tune stays well.