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i've often wondered the same thing--you'd think for speed-density fuel injection, all you need is RPM and MAP.

well, the MAP itself only tells you pressure, not density. the baro sensor combined with the AIT gives more insight for an actual density (really just gives you some values the ecu uses to pick compensation values from a lookup table), then that's used with the MAP to get an actual load value.
 

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Discussion Starter · #4 ·
spets on Aug/01/07 said:
It also allows the ECU to compensate for altitude changes, so the same car tune will work for both Denver and Florida.
i'm guessing compensating for altitude changes so that means it actually compensates for air density. does that mean when during the winter when it's cold and the air density is thicker it will compensate for that also?
 

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I was given this explanation at my EFI University class:

At different atmospheric pressures, the throttle plate will be open different amounts for the same manifold absolute pressure reading. The throttle plate's position has an effect on the volumetric efficiency. So the atmospheric pressure sensor allows correction for volumetric efficiency changes due to the throttle plate's position.
 

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Pretty much nailed it. Barometric pressure has a small but measurable effect on volumetric efficiency. The ECU uses a variety of sensors to calculate the density and volume of the air. The MAP, IAT, TPS, and APS are all used to calculate the air density. A standard formula for fluid dynamics is used to get a very close reading of exactly how much air is being fed to the engine. The ECU then uses this value to calculate the amount of fuel needed, and the engine timing that best fits. The O2 sensor is also used the fine tune the mixture. Blah, Blah, Blah...

EDIT: Think of it this way: the higher the air pressure, the more the air tries to enter the engine.
 

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Bringing this thread back from the dead.

From my research online just because you throw a code 13 BARO, that doesnt mean you have to replace the ECU. It could also mean that its reading conflicting numbers and stuff from the TPS, MAP, and BARO.

My question is that if it the actually BARO sensor, I have many ECU's, but different in OBD1,2a,2b, is there a way I can take one out of one ECU and put it into another? Also, is there a place that has the ECU layout with everything labeled so I know what I'm pulling out?
 

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PHANtastic:
I ran into this problem recently and had a cel. Used my code reader and pulled code
P1106 Barometric Pressure (BARO) Sensor Circuit Range/Performance Problem

In the service manual it says that the only way to fix it is to replace the ecu. In my situation I had to purchase another obdIIb ecu. In 2000-2001 integras the immobilizer will cause you to not swap ecus without doing certain things that I will not get into. If you take the ecu and your key down to Honda, they will recode everything.

Now my question for everyone is after I replaced my ecu with a working one, after driving around for 30 minutes I got the same cel again. The service manual shows the map, tps, and baro are all intertwined so would replacing the map be my next move?
 

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I ended up fixing my CEL 13 BARO like a week later. It turned out that it was just the MAP sensor. I had a handful lying around off various D's and B's engines. I never really worked on a GSR engine before but some of the MAPs have a gasket, if that gasket is broken is could cause a problem, or just the MAP itself is bad.

TPS sensor was an easy one for me, I did have an aftermarket throttle-body so I did mess around with that before. You just have to make sure its reading exactly .50 volts. Just need a paper clip and a multi-meter.
 

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I know this is an old thread. This reply is aimed toward those that mentioned owning a 2nd gen.

Uh. The PA sensor as it can be reffered to
or baro sensor on the 2nd gen integra

is located inside the passenger cabin.
Not in ecu.
Passenger side, remove kick panel to get access to it. (where the auto seatbelt module is. )
Its secured to the frame directly above the seatbelt module. With a single 10mm bolt. Its not in the ecu. For the 2nd gens.

Service manual for 90-91 integra provides location and. Diagnostic specs for troubleshooting.
 
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