IAT Default Temp on Open Circuit
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IAT Default Temp on Open Circuit
Everything I read says the IAT PID on a Ford (1999 5.4l) should read -40 degrees on an open circuit (harness DC'd). Mine switches to 100 degrees, plug it back in it goes back to reading the temp. What should I make of this? My mind says this would be the PCMs way of giving a default value to allow the vehicle to run decently, however this conflicts with all the posts I've read on this and other forums (plus a couple of videos).
The IAT PID when DC'd shows the fault. The IAT voltage PID when DC's shows it around 4.6v.
The engine is still running well but I thinks it because the PCM is compensating. I'm just trying to pinpoint a possible uncalibrated maf sensor (neg trims on idle, switches to positive on load). The maf has been cleaned w/CRC.
The IAT PID when DC'd shows the fault. The IAT voltage PID when DC's shows it around 4.6v.
The engine is still running well but I thinks it because the PCM is compensating. I'm just trying to pinpoint a possible uncalibrated maf sensor (neg trims on idle, switches to positive on load). The maf has been cleaned w/CRC.
Hotshot
Joined: Jan 2004
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From: St Louis
If the IAT is reading the air temp as approximately ambient (or a little higher due to underhood temps), it's fine. Leave it alone, no need to go down a rabbit trail and end up lost in the weeds.
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Well I am trying to track down an issue (fuel trims) and the IAT is one sensor that could affect it. And as mentioned the IAT was not acting like everything I've read from past threads (I think including one of yours) both on this site and others, which invites the question. As averse as I am to rabbit holes, I'm not sure this qualifies as one. Not sure what the harm is by asking if anybody had encountered this. That being said I did find this
https://www.carparts.com/blog/p0113-...it-high-input/
which talks about a default strategy for some IATs/PCM. Maybe the 99 Fords PCMs have this in them. I'm just surprised no one else had mentioned these numbers (100 degrees disconnected) previously. And maybe this post, if it comes up in a search, will let others know that -40 degrees might not be the only temperature to be seen while testing/diagnosing an IAT.
Just trying to share and gather information.
Now on to testing the mafs...
https://www.carparts.com/blog/p0113-...it-high-input/
which talks about a default strategy for some IATs/PCM. Maybe the 99 Fords PCMs have this in them. I'm just surprised no one else had mentioned these numbers (100 degrees disconnected) previously. And maybe this post, if it comes up in a search, will let others know that -40 degrees might not be the only temperature to be seen while testing/diagnosing an IAT.
Just trying to share and gather information.
Now on to testing the mafs...
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AJaa
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Dec 10, 2017 05:44 AM
