Outside air temp sensor reading too high...
09-17-2009, 03:46 AM
#1
Outside air temp sensor reading too high...
Last few days my outside air temperature sensor has been reading about 20 degrees higher than it should. Has anyone had anything similar happen? Im hoping that sensor is not used for the intake air temp, otherwise it will throw off A/F ratio and be bad for the engine.
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Mdarosa92 (07-20-2019)
09-17-2009, 05:51 AM
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190D 2.5 (x2), 190E 2.6, W202 C240,W202 C43 (C55), W210 E55, W212 E250CDI
The ambient temp sensor has nothing to do with the engine intake temp sensor.
The ambient temp sensor sometimes dislodges and falls in behind the front bumper and picks up engine heat, this causes high reading that won't come down or don't come down by much once you start moving.
A disconnected sensor causes a reading around 85C/180F
The other thing that you must remember is that the sensor changes very slowly, if at all, when the vehilce is below 20kph to help prevent wildly changing readings.
The ambient temp sensor sometimes dislodges and falls in behind the front bumper and picks up engine heat, this causes high reading that won't come down or don't come down by much once you start moving.
A disconnected sensor causes a reading around 85C/180F
The other thing that you must remember is that the sensor changes very slowly, if at all, when the vehilce is below 20kph to help prevent wildly changing readings.
09-17-2009, 08:16 AM
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'09 C63 AMG
FYI -- every car I've ever driven that showed the outside air temp always showed the temp to be at least +3-5 degrees F higher than it really was. It seems car thermometers are never accurate, probably b/c of the extra heat that is produced by the engine and surrounds the car. 
