HELP! IAT sensor dropping below zero the more you drive
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From: Nashville, TN
HELP! IAT sensor dropping below zero the more you drive The car is a 2007 c6z. If you start the car cold it reads ambient or close to it on the IAT, if you start hot it reads hot like you would expect, but drive 5 mins down the road and it steadily drops to below zero when its 80deg outside... Either i've figured out how to bend the laws of physics or there's something really messed up going on. I've replaced the MAF/IAT sensor and its doing the same things.. I'm getting lots KR because the car thinks its cold out and i'm at a loss for how this could happen??
Thread Starter
TECH Enthusiast
iTrader: (4)
Joined: Dec 2005
Posts: 612
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From: Nashville, TN
Its not an open circuit tho. It reads temp just the longer you driver the lower it gets. Over a 10-15 min period the car starts at normal temps/ambient and starts slowly dropping a degree or two every minute. It never gets to the temp that reads if you disconnect the sensor (-40) the temp doesnt jump around or bounce its a steady decline. weirdest thing ive ever seen.
Why is this bothering you? Colder air on a warm day just means more power!
I kid, I kid...I also agree that it's some sort of short or other wiring issue further down than where it connects to the actual sensor. If it was straight up bad it would read -40 like you said. But seeing as how it's just a little bit less than normal and it continually goes down then it's probably just shorting somewhere and it *thinks* it's reading a different temperature than it actually is.
I kid, I kid...I also agree that it's some sort of short or other wiring issue further down than where it connects to the actual sensor. If it was straight up bad it would read -40 like you said. But seeing as how it's just a little bit less than normal and it continually goes down then it's probably just shorting somewhere and it *thinks* it's reading a different temperature than it actually is.
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Verdad Gallardo It's conceivable that the problem is inside the PCM,
which has to source a sense current onto the IAT
thermistor. If that circuitry has a thermal drift, etc.
the PCM's self-heating or engine bay heating could
drift that current, and the voltage read.
Might consider putting a 1.5K metal film resistor
(I know, everybody keeps precision resistors handy)
and see whether the "temperature" from that is
moving like the IAT.
In a heat-soaked engine bay the IAT will creep down
until it plateaus at ambient. What is your initial and
final (if it ever reaches a final value) reading?
which has to source a sense current onto the IAT
thermistor. If that circuitry has a thermal drift, etc.
the PCM's self-heating or engine bay heating could
drift that current, and the voltage read.
Might consider putting a 1.5K metal film resistor
(I know, everybody keeps precision resistors handy)
and see whether the "temperature" from that is
moving like the IAT.
In a heat-soaked engine bay the IAT will creep down
until it plateaus at ambient. What is your initial and
final (if it ever reaches a final value) reading?