unTAmedLS1

So I keep getting a dtc for map voltage low and one for high. So I buy new pig tail and connect it and the same thing still.
Key on= 1.019 volts on freescan and 5.0volts at the connector
Car idling= between .79-.90
Here is the weird thing..with the key on and connector not plugged into the sensor freescan says .140 volts
I also tried a new map sensor with the same results...
Also I pulled all the plugs today and the car is running lean as hell...I tested fuel pressure and it was 44 which is right about what it should be...
Mail order tune from madwolf with obd1 conversion...
The rest of my info on my car can be found here

I will seriously pay 50 dollars to the person that gets my car running normal again... No lie I am an honest person

I am so fed up I just want to get this stroker going or it will be a parts car soon

shoebox

Have you checked the wiring between the PCM and sensor? I am not used to looking at voltage readings, but actual MAP readings in KPa or Hg.

Injuneer

With the connector off, you should get +5V between the gray and black wires. You shouldn't see any voltage between the green and black wires. Sounds like you have a short in the wiring harness, not in the pigtail.

[EDIT] There's a conversion chart from volts to kPa to "Hg in my Scanmaster writeup.

1.1V = 8.9"Hg = 30kPa
1.7V = 11.8"Hg = 40kPa
2.2V = 14.8"Hg = 50kPa
2.7V = 17.7"Hg = 60kPa
3.3V = 20.7"Hg = 70kPa
3.8V = 23.7"Hg = 80kPa
4.4V = 26.6"Hg = 90kPa
4.9V = 29.6"Hg = 100kPa

Alvin@pcmforless.com

I agree, with the key on engine off voltage should be in the mid to high 4v's.. Maybe even 5 flat. Sounds like a short or pinch between the map and computer, or a bad ground.

Injuneer

With the key on/engine off, the sensor reads the barometric pressure. At sea level, you should see about 5.0V. In Denver, you might only see 4.0V.

unTAmedLS1

see the weird thing is that I do see 5 volts when I hook a multimeter up to the connector when its not plugged in the sensor with key on. But I dont see it in freescan when I plug the connector into the sensor

Injuneer

Which wires are you measuring the voltage on? Black and grey provide the ground and +5V reference. The green wire is the variable signal voltage return.

unTAmedLS1

I think it was the black and gray i was measuring...So what should I do? groundthe multi meter and hook the positive to green? Also what is the order the wires should be plugged into the pigtail from left to right with the clip part facing up like if it was plugged into the sensor

unTAmedLS1

also what does it mean that the sensors not plugged in but i still see .140 volts on freescan

turbo_Z

What is the barometric pressure reading? Not sure if freescan shows it but I know datamaster does and you can try it free for 20 logs to see what its showing. If the baro is legit then the MAP sensor is good but then like others have said it should show the same reading with the key on but engine not running.

Also if you install datamaster you could send the logged file around for others to look at.

Injuneer

You're not reading the replies you are getting.

You should always see 5V when you measure between the black wire and the gray wire... whether the harness connector is on the sensor or not.

Reading between the green and black wire, with the connector on the sensor, should match the reading you get with a scanner. That's the signal going to the PCM.

I don't think you should see any voltage between the green wire and the black wire when the connector is off. It should represent an open circuit.

At idle, you should be seeing about 1.2V between the green wire and the black wire. Key on/engine off, you should be seeing the voltage that corresponds to the barometric pressure... about 5V at sea level, and 4V at 5,000ft elevation. Your scanner should show you the barometric pressure, and it should be showing about 30"Hg (100kPa) at sea level, and 25"Hg (85kPa) at 5,000-ft.

The wiring order on the MAP sensor is:

Pin A - Back
Pin B - Green
Pin C - Gray

unTAmedLS1

Ok I understand now...
So Im wondering what could be causing the meter to showvoltage when the car is not on...When I put the negative on the black and the positive on the green I see .140 so I am just wondering where the voltage could be coming from..Thanks for your help and sorry for sounding like an idiot.. IM just really frustrated now because I have put so much time money and effort into this and this is the only reason my car isnt running right...I wish I had someone nearby that could help me and wouldnt charge out the *** for it

unTAmedLS1

k heres what I did I soldered all connectors made sure they were right...
Final Voltages of everything
Key on connector unplugged=.104 on freescan
key on connector unplugged volt meter on brown and black wire=4.7volts
Key on connector unplugged volt meter on brown and green wire= 5.2 volts
key on connector unplugged negative of voltmeter on ground positive on green wire in between .1 and .2
key on sensor plugged in freescan says .225 and free scan also said baro was .225
also relocated pcm ground to motor mount bolt same thing

unTAmedLS1

I have no problem buying a new harness I just want to make sure if I do that it will work and fix my problem...If you guys honestly believe that will solve my issues then let me know.. I really have no money left and just want the enjoyment of my car again...Thanks to everyone for their help