How do I test the MAP Sensor?
 

Hey,

Does anyone know how to test the MAP sensor? The manual says to get a voltage reading with the sensor unplugged--how is that possible?

What do I test and should the car be running or not while I test. Again, manual says to test at normal operating temperature with all electrical load off, but since it's telling me I should get a voltage reading when there is, as far as I know, no power going to the sensor (since it is unplugged), I don't trust the manual.

Thanks,
Clint Fralick
Struggly@hotmail.com

Clint,

I just did this a few days ago, and the manual is confusing on the MAP sensor test. Get a couple of medium-large safety pins and insert one in the middle terminal and the other in the terminal closest to the driver's seat. Just piggy back off the rear of the electrical connector while it is still plugged in, and you should be set. Also make sure the key is on, engine is off while doing the testing. If you don't have a vacuum tester, just start the car and check the readings with it running to determine if it reading your idle vacuum correctly. Hope this helps!


Jon
'93 MB Touring
'85 GSL-SE

If you have the Apexi Power FC it will give you a voltage readout.

bump

What is it listed as in the Power FC? I'm guessing it's under that 'sensors' menu which one though and what are the specs for it to be good/bad?

Here is mapping from my car with a stock map sensor.

Maybe I am overlooking it. I need the correct specs and how to test the MAP sensor at IDLE. I have looked through the Factory Service Manual a couple times as well but am not seeing anything there either. :(

There are three wires going into the connector. Left to right, a brown and white reference voltage, a black and green ground and a green and yellow signal. Either rig up three jumper wires or carefully stick pins into the back of the connector so you can .

1) Engine running, warm and at idle, voltmeter + lead to reference (BW), neg lead to ground(BG) - test to make sure you are getting 5v power.

2) Positive lead to sensor ground(BG), negative lead to battery ground, test for voltage drop, should be very low. I get .06 volts.

3) Positive lead to sensor signal (gy) and negative lead to to ground (BG)- at idle 1.3 to 1.6 volts.

4) Disconnect the vacuum hose. At zero vacuum you should get 2.4 to 2.8v. I got a 2.6v

5) Use the pump to create vacuum. Vacuum "sucks the voltage out". The manual shows idle, 0, and 19.7 inches so pump the vacuum up to 20. The book says 1.25 to 1.55v. I got 1.14 at 20 inches.

Hope this helps.

I believe its the PIM voltage. I think thats still it, I haven't had the car on in about a year.

Thanks for all you help guys, especially tcb100.

I will try to test the sensor out sometime this afternoon. Wish me luck.

My MAP Sensor results

4.97V
2.02V :confused:

2.00V :confused:

2.5V

Couldn't complete. No vacuum pump/tester.

Not sure what to think of this. When I take the vacuum line off the MAP sensor the change is noticible, but not too drastic of a difference.