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Atmospheric Pressure Sensor - Where'd it go after 2002


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11 replies to this topic

#1 subaruVWnut

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Posted 23 November 2005 - 06:05 PM

I just purchased a 2002 Legacy GT that was wrecked and plan to pull the engine to put into a VW Vanagon. I've pulled several of these for this purpose.....but in pulling the engine I see that this car does not have the atmospheric pressure sensor that earlier models had mounted in the engine bay on the passenger side fender. A 2002 Impreza RS I pulled an engine from a year ago still had that sensor.

Anyone know anything about Subaru changing to a different system in late 2002 to adjust for altitude......to send altitude info to the ECU?? The dealer tells me that none of the engines from 2002 on have the sensor.

The vehicle this engine will go into will be making frequent trips to the mountains and the owner wants to make sure it can adjust easily to altitude changes.

Warren C.

#2 nipper

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Posted 23 November 2005 - 06:27 PM

I think what you are talking about is not an MAP sensor, but a PCM, a pressure sensor with a solenoid that switches between manifold pressure and atmospheric pressure. Sort of an odd way of doing it, but then again i am only working form a 98 manual, so i dont know if it is the same.


nipper

#3 blitz

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Posted 23 November 2005 - 09:08 PM

Sometimes it's called a BAP sensor (barometric absolute pressure). My '02 has it on the passenger fender well, but I can't find it anywhere on anywhwere on my '00. :confused:

Maybe there are different mounting locations depending on the year model or trans but I don't have that info.

#4 Strakes

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Posted 24 November 2005 - 11:16 AM

Wasn't that the year that Subaru modified the MAP/BAP system or whatever you call it? When Cobb designed a cold air intake, the parts decription said something about 2 or 1 sensor systems and to call with your VIN for the correct CAI and the changover year was 2002. What does it look like? I've got a 02 GT built in Sept 2001 and I can go look for it on my car if you post a pic of the item you're looking for.

#5 Setright

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Posted 24 November 2005 - 02:02 PM

Urabus, eh???


What do you need the sensor for? Are you moving the transmission over too?

#6 blitz

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Posted 24 November 2005 - 02:07 PM

Wasn't that the year that Subaru modified the MAP/BAP system or whatever you call it? When Cobb designed a cold air intake, the parts decription said something about 2 or 1 sensor systems and to call with your VIN for the correct CAI and the changover year was 2002.

Pretty sure your thinking of the MAF (mass air-flow) vs MAP (manifold absolute pressure) - two different types of fuel injection systems.

The atmospheric pressure sensor (that's what Subaru calls it) is just for trim. It compensates for altitude by accordingly reducing the fuel in the fixed maps. It might even bump the timing up a little bit too, not sure about that tho.

What does it look like? I've got a 02 GT built in Sept 2001 and I can go look for it on my car if you post a pic of the item you're looking for.

It's a black plastic cube about an inch on a side, most likely says Bosch or Denso on it and has a 3-pin connector.

1. +5 ref.
2. analog output.
3. ground ref.

The location is the the front of the passenger shock tower. It's held to a little bracket by a single bolt.

#7 blitz

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Posted 24 November 2005 - 05:16 PM

Photo, compliments of Lawsonmh15 from his grounding mod thread of 9/05/05. The thing labeled as: "Some Type Of Air Sensor" is the atmospheric pressure sensor.

To be clear, it is also referred to as the BAP by others (Ford, etc.).
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#8 subaruVWnut

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Posted 25 November 2005 - 01:35 AM

Yes the sensor in the photo is what I am referring to as the atmospheric pressure senssor.

But it is not there on the 2002 Legacy GT I am dismantling.

So I'm assuming Subaru has a different way of sensing altitude or barometric pressure. I'd like to know how this sensor has been replaced.

Warren C.

#9 nipper

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Posted 25 November 2005 - 09:51 AM

isnt that it on the strut tower?

Is there a freindly subaru parts departemnt that you have dealt with, you can ask them topoint it out to you?

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#10 Strakes

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Posted 25 November 2005 - 10:41 AM

Thanks for the pic. My 02 GT does not have that sensor that you have on your pic. Mine has 2 sensors between the air filter and the intake. One mounted on top, just prior to the throttle...maybe the throttle position sensor? The other is on the passenger side of the throttle body area. A black small square box with 3 wires.

#11 blitz

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Posted 25 November 2005 - 12:19 PM

Yes the sensor in the photo is what I am referring to as the atmospheric pressure senssor.

But it is not there on the 2002 Legacy GT I am dismantling.

So I'm assuming Subaru has a different way of sensing altitude or barometric pressure. I'd like to know how this sensor has been replaced.

Warren C.

IMO, this sensor would be a requirement on any modern F/I system with an exhaust emissions target.

Digging a little deeper, I've learned that some Subaru models have this sensor as an integral part of the ECU. Don't which ones tho.

#12 blitz

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Posted 25 November 2005 - 12:27 PM

Thanks for the pic. My 02 GT does not have that sensor that you have on your pic. Mine has 2 sensors between the air filter and the intake. One mounted on top, just prior to the throttle...maybe the throttle position sensor?

If it has 2 wires, it's the Intake Air Temp (IAT) sensor. If it has 3 wires and it's mounted onto the end of the throttle shaft it's the Throttle Position Sensor (TPS).

The other is on the passenger side of the throttle body area. A black small square box with 3 wires.

Manifold Absolute Pressure (MAP) sensor.




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