MAP Sensor issue
 

I'm having an issue with the map sensor. When I connect my code scanner it gives a code for my MAP sensor having low voltage. When the engine is running and I have the scanner connected the MAP sensor is showing 3 hg and it never changes whether it s plugged in or not, or if its at idle or around 4000 rpms. I check the reference voltage and its at 5 volts. I'm looking for some info on what could be the problem. So please speak up :flag:

Thanks in advance:
Robert

Re: MAP Sensor issue
 

Might sound dumb, but...maybe the map sensor is broken. :)

Re: MAP Sensor issue
 

If you've checked the wiring like you say, then i'm with BR3W, sounds like you need to try another sensor.
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Re: MAP Sensor issue
 

ls1nova71,
I thought about that but, I bought that 1 from Autozone a couple of months ago. The one I bought was for a LS 6 to match the intake. Is it possible that I should of us the one for a 5.3L instead? I'm not sure if there's a difference between the two. I have the MAP sensor on the 5.3L truck intake, maybe I can see if that one will fit on the LS 6 intake.

Thanks for the info,
Robert

Re: MAP Sensor issue
 

the truck and ls6 sensors are different but use the same plug. I'm guessing they are either scaled differently or something similar?

They are 2 different part numbers, so it couldn't hurt to plug the truck one in and see what happens.

Re: MAP Sensor issue
 

Not sure if the values are different but I would imagine they would be. I don't know if the truck sensor will fit the ls6 intake for a permanent installation, but you could temporarily hook it up to see if it fixes your problem. All it needs is vacuum, it doesn't need to be mounted solid to the intake, you could hook it up with some vacuum hose.
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Re: MAP Sensor issue
 

ls1nova71 & BR3W thanks for the info. I will try the truck intake MAP sensor and see if it makes a difference. I keep my fingers crossed that it will. Again thanks for the help. Robert

Re: MAP Sensor issue
 

A 1-BAR MAP sensor is a 1-BAR MAP sensor. A LM7 & LS6 use a 1-bar map sensor. They function the same way, You could wire in a MAP sensor from a '83 cross-fire Camaro on a LS & it would work.

Even with a 2-BAR or 3-BAR the voltage would change....though be wrong for a N/A 1-bar tune.

Check your wiring, Though buying a aftermarket sensor does make me question the part.

A 1 BAR MAP sensor reports barometric pressure times one, which is approximately 14.7 psi or 30in/Hg (inches of mercury). As an example, a typical three wire MAP sensor has 5 volts and ground to power the circuit. The signal circuit, or return voltage to the computer, is about 4.5 volts at barometric pressure of 14.7 psi; this measurement is taken at key on engine off. The sensor can withstand about 1.5 BAR of pressure, but the return voltage will peak out at about 4.8 volts. This type of sensor is designed for a normally aspirated engine to read a negative pressure, or vacuum, at a typical barometric pressure, When vacuum is high (idle, decel) the sensor will read low voltage....Around 1.50 volts.

Re: MAP Sensor issue
 

so its not like with a TPS where the working range is different within the sensor? I honestly don't know. (i.e how some tps read 0-5v or 0-10v or 5-0v)

If so, will ANY 2 or higher MAP sensor work in a FI application if its wired correctly? (i guess im asking if theres a cheap option to do that for FI, I assume vs a SD application)

Not trying to sidetrack the thread.

Re: MAP Sensor issue
 

Any GM 1 BAR map will swap, Not sure on other makes?

2 BAR & 3 BAR map sensors are scaled differently...2 BAR or 3 BAR simply mean two or three times above barometric pressure. The sensor will measure each direction, vacuum or pressure. These are only used in Boosted applications & A PCM with a 1-BAR tune will need a custom tuned for a 2 or 3 BAR map

•1 BAR is for a normally aspirated engine
•2 BAR will handle a forced induction up to 14.5 psi of boost
•3 BAR will handle a forced induction up to 29.0 psi of boost

Re: MAP Sensor issue
 

Clinebarger, Thanks for the info. I did double check the wiring for voltage and resistance. I also did the shake test with the help with help from a friend and the wires seemed fine. I will take the MAP sensor back and get another one to try. I will try to use the one off the truck intake withsome adaptors. I'm not sure the next step after that if nothing changes. At one time I thought that maybe it was the scanner, but, everything else seems ok through the scanner. I don't think the truck will be on the road this year. (School tuitions are being paid so the money for the truck has slowed down.) Maybe I can loaded on the trailer and get it to a tuner or have someone come by with a tuner program to check it. Any way if anyone else has any ideas please let me know. This is the first time I ever worked with an LS style engine and so far it hasn't been to bad. Thanks again for the info. Robert:chevy: