Hello All,

So I went to start my car to no luck, car stutters and quickly dies.. After much trouble shooting, and fixing a few issues. I finally narrowed down the major issue to an unresponsive MAP sensor. When I view my diagnostics through Neptune the MAP reading stays right around 28in/hg.

I believe it is the MAP sensor itself, because the reading changes from ~30in/hg to 28in/hg depending on if the ignition is on or not, implying the ECU is reading voltage levels. (it also fluctuates slightly). Also, it seems like everything else is working so I find it hard to believe that just the port the MAP sensor reads on would go bad. I could be wrong though.

My question is, what sort of tests can I do to verify that the MAP sensor is non responsive? If that is the case, it is a simple matter of swapping in a new MAP. (I would just do this, but I don't have one, so I would need to go buy one).

Thank you so much for your time!

Matt

 

Measure the map sensor signal wire voltage using a multi-meter.

 

At key off there's a default value, so you can't compare that. Follow mtber's advice, though.

 

What voltage am I looking for? I assume the voltage changes with pressure, but what range is acceptable?

My other thought was to hook a potiometer up in place of the MAP sensor, and vary the pot, if the reading in NepTune changed with the pot, I would know the ECU is still reading, and it's a bad MAP. But I need to make sure not to burn out the ECU by exceeding the voltage limits of the input pin.

Matt

 

At key on engine off you shouldn't be reading 28-30 inHG, so you're checking to see what voltage the MAP sensor is outputting. You can also right click on a gauge set to MAP and choose show voltage/real-world to see if the ECU sees the same voltage.