Testing A Map Sensor

[M3Evo 0]

Can anyone tell me how to test a MAP sensor?

 

It's a Magnetti Marelli (sp?) one.

 

According to emerald's literature, pin C should be the signal, pin B should be earthed and pin A should be the supply.

 

I'd have thought that if I connected a multimeter set to read resistance to pin C and either pin A or B, I should get a variation in reading if I vary the pressure in the little pipe?

 

I tested mine in this way and there was no change, so I wired it up to the Emerald to see if that had any more luck, but it just reads a constant -0.6bar, even with the engine off!

 

Just borrowed miamistu's MAP sensor and testing it with the multimeter, it's resistance across any combination of pins doesn't change

 

Also, is the little bit of metal around one of the mounting holes on these sensors supposed to be earted or is it just to conduct heat away?

 

Cheers!

 

Alex

[Super Josh 4]

Well it's not a passive sensor( like a coolant temp sensor etc) where its resistance changes. You need to wire 5 volts up to the two supply pins and then you can measure the voltage from the output pin. Connect a piece of tubing up to the sensor and suck, whilst observing the voltage output. You'll be able to get the specs of the web, but if you are just looking for a dead sensor then make sure the voltage swings nicely from roughly 0.2 - 0.3 V to 4.5 - 4.8 Volts max, as you suck.

As for the metal around the mounting hole, how many pins does the sensor have? If only two then it'll definately be a ground pin. If it has three, put a multimeter between the ground pin and the mounting hole to see if they are connected.

 

 

Josh

[M3Evo 0]

Ah haa, was thinking that the signal pin might be like the wiper in a variable resistor or something.

 

It's a 3 pin sensor and the metal bit around the mounting hole doesn't appear to have any continuity to the pins

 

Cheers!

 

It's like this one BTW: