Need help finding correct BAP sensor!

[stang_380]

I have a 90gt 5-spd with 351 swap and it needs a BAP sensor, but i cant figure out which one to get. I accidently tossed the original sensor and im having trouble finding the correct replacment.

I purchased BAP sensor E8EF 12A644-A1A with wire colors: blk/wht, org/wht, and grn/blk.

Problem is the color of the wires on my cars harness are: gry/red, grn/blk, brn/wht.

Why dont they match? Could my car have different computer?
My computer has the following numbers on it if it helps. EECIV SFI MA 12 A9P and E9ZF-12A650-C2A can you please help me identify my computer and what BAP sensor i need.

 

[vristang]

I have a 90gt 5-spd with 351 swap and it needs a BAP sensor, but i cant figure out which one to get. I accidently tossed the original sensor and im having trouble finding the correct replacment.

I purchased BAP sensor E8EF 12A644-A1A with wire colors: blk/wht, org/wht, and grn/blk.

Problem is the color of the wires on my cars harness are: gry/red, grn/blk, brn/wht.

Why dont they match? Could my car have different computer?
My computer has the following numbers on it if it helps. EECIV SFI MA 12 A9P and E9ZF-12A650-C2A can you please help me identify my computer and what BAP sensor i need.

Your computer is for an Auto 5.0, MAF.

I don't think the colors of the wires will cause an issue. Ford changed the wire colors from time to time.
For example, my 90GT has the wire harness of a 91.

If you are concerned the best thing to do would be to call Ford or a dealership.
They should be able to tell you if you have the correct part number for use on a car originally equipped with the A9P computer.

Also, some online parts stores can be used to verify part number applications. Look up the appropriate BAP sensor number for a 92 Automatic 5.0. This year should be the same as the A9P computer you have.

Personally though I would install the sensor and see what happens.
Run the car for a few minutes, getting it up to temperature, then pull the diagnostic codes.

Wish you luck,
Let us know what you find out.

jason

 

[310stanger]

forgive me if this is a stupid question but where is this sensor located? ive never heard of it before and im interested in it and what its function is? if you have a bad one can it make for poor driveability?

 

[vristang]

forgive me if this is a stupid question but where is this sensor located? ive never heard of it before and im interested in it and what its function is? if you have a bad one can it make for poor driveability?

The only stupid question is the one that isn't asked

The BAP (Barometric Air Pressure) Sensor is mounted on the firewall. It looks exactly the same as the MAP (Manifold Air Pressure) Sensor (used on Speed Density cars), except the BAP does not have a hose attached to it.
A MAF equipped car uses Barometric Pressure.
A SD car uses Manifold Pressure (vacuum).

The MAF computer uses the BAP to adjust the fuel and timing according to atmospheric pressure changes. This means that your timing will automatically adjust when you drive up a mountain pass, or cruise back down to see level.

If the BAP has failed the computer will get false information about the atmoshperic conditions, and therefore, make poor decisions on how to adjust the timing.
For example, at sea level a failed BAP could be sending a signal to the computer indicating that the atmospheric pressure is much higher than it really is. Obviously, timing would not be optimal.


jason

 

[Boss 351]

Since we're on the subject... can we relocate this sensor and have it still work? Like inside the fender or something? If we mount it lower would that effect the readings at all?

 

[jrichker]

Since we're on the subject... can we relocate this sensor and have it still work? Like inside the fender or something? If we mount it lower would that effect the readings at all?

The sensor isn't sensistive to its mounting location, as long as you don't submerge it or locate it in an area that traps air & causes pressure to build up.

Note that a failed sensor will set code 22.

 

[Boss 351]

thanks for the info

 

[310stanger]

The only stupid question is the one that isn't asked

The BAP (Barometric Air Pressure) Sensor is mounted on the firewall. It looks exactly the same as the MAP (Manifold Air Pressure) Sensor (used on Speed Density cars), except the BAP does not have a hose attached to it.
A MAF equipped car uses Barometric Pressure.
A SD car uses Manifold Pressure (vacuum).

The MAF computer uses the BAP to adjust the fuel and timing according to atmospheric pressure changes. This means that your timing will automatically adjust when you drive up a mountain pass, or cruise back down to see level.

If the BAP has failed the computer will get false information about the atmoshperic conditions, and therefore, make poor decisions on how to adjust the timing.
For example, at sea level a failed BAP could be sending a signal to the computer indicating that the atmospheric pressure is much higher than it really is. Obviously, timing would not be optimal.


jason

Thanks for the very well written, and insightful response. The definitive answer i was looking for. now is this sensor something that only gets replaced when it fires a code or can it be cost effective to change if the car is lets say as old as my car. my car is a 1990.

 

[vristang]

Thanks for the very well written, and insightful response. The definitive answer i was looking for. now is this sensor something that only gets replaced when it fires a code or can it be cost effective to change if the car is lets say as old as my car. my car is a 1990.

As far as I know, my 90 GT still has the factory BAP

I have suspected various sensors of being 'bad' but can't remember a single instance of a ANY sensor actually failing on my car.
I'm not saying that the sensors don't fail, just that in my 225k miles, I haven't had any fail.

IF the sensor is not terribly expensive, it may be worth replacing it. Piece of mind is worth something.
How much it is worth will be up to you though.

I'm curious what other have to say on this topic


jason

 

[stang_380]

Thanks for the help everyone, i would like to be able to tell you if it worked or not but i just stored my car. I did how ever install this sensor last spring, I guessed which wires go together because they didnt match and I hope I guessed wrong because i had code 22 flashing me all year. Now that the car is in storage i finally used the wiring diagrams to interperet the correct different wire colors. So now that i know that when i get the car back ill make the right connections and hope that solves the problem.
Would having this sensor hooked up wrong been why i had poor performance and popping through the intake?

Thanks again for your help everyone.
Erik

 

[jrichker]

Code 22 MAP (vacuum) or BARO signal out of range. The MAP or BARO sensor is pretty much the same sensor for both Mass Air & Speed Density cars. The main difference is where it is connected. Mass Air cars vent it to the atmosphere, while Speed Density cars connect it to the intake manifold vacuum. Its purpose is to help set a baseline for the air/fuel mixture by sensing changes in barometric pressure. The MAP or BAP sensor puts out a 5 volt square wave that changes frequency with variations in atmospheric pressure. The base is 154 HZ at 29.92" of mercury - dry sunny day at sea level, about 68-72 degrees. You need an oscilloscope or frequency meter to measure it. There is no way you can use a common cheap voltmeter or DVM to accurately measure the output signal.

The MAP/BARO sensor is mounted on the firewall behind the upper manifold.

Baro or MAP test using frequency meter - run the test key on engine off. The noise from the ignition system will likely upset the frequency meter. I used a 10 x oscilloscope probe connected from the frequency meter to the MAP/BAP to reduce the jitter in the meter's readout.

If it is defective, your air/fuel ratio will be off and the car’s performance & emissions will suffer

Some basic checks you can make to be sure that the sensor is getting power & ground:
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery cable. It should be less than 1.5 ohm.

The following power on check requires you to turn the ignition switch to the Run position.
Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or EGR sensors. Use the black/white wire for the ground for the DVM.