IAT Temperature Incredibly High (240º F) Good Sensor

[jbarzelatto]

After an engine swap, my IAT temperature is stuck at a VERY high temperature. Approximately 240 degrees, when my ambient temperature is 70 degrees aprox.

I have tried several sensors so the sensor is not the bad one. I have an INJENN CAI. But to test, i even went back to the original one and problem persisted. Attached is a pic of the scanner, its in spanish and temp is in C, but i translated that.

Please help!

[juld0zer]

There is two intake air temperature sensors.
I can't remember if ISTA will show both but most scanners will only show the reading for the second sensor, which is the charge air temp and pressure sensor (TMAP). It is located at the bend in the charge pipe nearest to the throttle body.

This is why changing the intake did nothing.
In the morning, check it again. If the intake temperature reading does not change then inspect the TMAP sensor and wiring. If you can observe the temperature close to ambient first thing in the morning and watch it rise then you have another problem

[bbnks2]

Originally Posted by juld0zer

There is two intake air temperature sensors.
I can't remember if ISTA will show both but most scanners will only show the reading for the second sensor, which is the charge air temp and pressure sensor (TMAP). It is located at the bend in the charge pipe nearest to the throttle body.

This is why changing the intake did nothing.
In the morning, check it again. If the intake temperature reading does not change then inspect the TMAP sensor and wiring. If you can observe the temperature close to ambient first thing in the morning and watch it rise then you have another problem

You can also just swap the MAP with the TMAP sensor. If that works, you know you had a bad TMAP.

[juld0zer]

Is that the one in the intake manifold? I thought they were pressure only?

OP is your engine an N54 or N55?

[bbnks2]

Originally Posted by juld0zer

Is that the one in the intake manifold? I thought they were pressure only?

OP is your engine an N54 or N55?

On an N55, the sensor that is in the intake tract (MAF) is the same sensor that is on the charge-pipe (TMAP). You can swap them. They are the same part number.

IAT reading is from the one on the charge-pipe.

[jbarzelatto]

Originally Posted by bbnks2

On an N55, the sensor that is in the intake tract (MAF) is the same sensor that is on the charge-pipe (TMAP). You can swap them. They are the same part number.

IAT reading is from the one on the charge-pipe.

Originally Posted by bbnks2

On an N55, the sensor that is in the intake tract (MAF) is the same sensor that is on the charge-pipe (TMAP). You can swap them. They are the same part number.

IAT reading is from the one on the charge-pipe.

Hey guys thanks for the answer! Forgot to mention I tried different sensors, on both the chargepipe tmap and the Maf on the intake. In my case though they are different. Some n55 versions are the same, some aren't. That's why for jb4 n55, there is a harness A and HARNESS B option. Any other ideas? I'm thinking the dme might be messed up. :/

[juld0zer]

N55 has always had a MAF but you can't install it where the TMAP sensor is in the elbow of the chargepipe.

OP, do you have an infrared thermometer to verify the chargepipe section nearest to the throttle body is not anywhere near as hot as the DME says it is? Could you remove the JB4 and check again? 115*c sounds more like oil or coolant temp. Who did the engine replacement? Was it like for like or...?

[inevitab1e]

Stuck at 240 degrees? Sounds like the oil temperature reading. That's where my oil temp sits when fully warmed up.

[GreaseMonkey7]

Sorry to resurrect this old thread, but I'm currently dealing with the same issue on a 2012 535i with unknown history. Anybody know if this was ever resolved and if so what fixed it?


IAT Shows 240-242F with key on and engine off, even if the engine is cold. All other temp sensors show 86F, which is roughly the temperature in my shop.

Boost pressure shows 5 inHG under same conditions, all other pressure sensors report roughly 29 inHG, which is correct atmospheric pressure.


I've tested multiple sensors, including a new one from BMW. I have good 5V reference voltage and ground to the sensor. No resistance in signal wires from sensor to DME.

After finding this thread, I'm starting to think this vehicle may have had the engine swapped and the sensor or DME may not match the VIN.

Any help is appreciated. Thanks in advance.

[dtla1]

Long shot, but I've heard a battery that's almost dead might make weird shit happen.

Long shot... Also, if you have a JB4, remove it, then diagnose.