Tricked-Out-Toy

iTrader: (4)

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??

jimmyblue

iTrader: (11)

Open circuit reads -40F or so. This will freak out a lot of
things. Look for connector flakiness and other such things.

Tricked-Out-Toy

iTrader: (4)

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.

RonSSNova

iTrader: (3)

Did you try replacing it?

Tricked-Out-Toy

iTrader: (4)

Yup. Replaced it and it did the exact same thing....

RonSSNova

iTrader: (3)

Possibly a wiring issue then between the sensor and the PCM.

Would be interesting to replace the sensor with a 5k ohm pot set to 2.5k and see if it behaves the same.

redtan

iTrader: (5)

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.

RonSSNova

iTrader: (3)

Is the iat stock for your car?

If not, there is a table in the eng diagnostics that needs to be changed to match the sensor. Just throwing this out there

jimmyblue

iTrader: (11)

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?