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Ambient air temperature sensor malfunction?

71K views 43 replies 15 participants last post by  Stinger9 
#1 ·
I got a check engine light on so I went down to my local Autozone and it printed out that my ambient air temperature sensor was either due to open or short circuit condition. They reset the code for me, and the next thing I know my A/C was not working for 5 minutes or so, then came back on.

So can this thing affect my A/C performance, and where is it located?

Ever since my bumper became dislodged the A/C has acted up intermittently, so I am guess the sensor is somewhere in the front bumper/spoiler?

Autozone said they do not sell the part/s, so how expensive of a fix is this?
 
#4 ·
Errr, that's not a picture of where it's located

Your ambient temperature sensor is located in a recess under your front bumper on the driver's side if you live in the USA. Scrape it or dislodge it and it will play havoc with your A/C functioning. Usually it will effect real crazy readings when you selection outside air temperature on the stalk computer.
I think the sensor is about 80, just guessing, and those who know say there is a bracket you will probably need too.
Replacement cures what ails you. I have never had this problem.
Let us know how you make out.
 
#5 ·
Your ambient temperature sensor is located in a recess under your front bumper on the driver's side if you live in the USA. Scrape it or dislodge it and it will play havoc with your A/C functioning. Usually it will effect real crazy readings when you selection outside air temperature on the stalk computer.
I think the sensor is about 80, just guessing, and those who know say there is a bracket you will probably need too.
Replacement cures what ails you. I have never had this problem.
Let us know how you make out.
The drivers side splash guard in front became dislodged due to the mishap I had with the bumper(in another recent thread). When it came off, a long piece of wire along with the AAT sensor came with it. I suspect I could splice it back into the existing wiring if I could find it as a temporary fix.

As you said it is playing havoc with my A/C giving me reading ranging from -40 to +122. Of course when it reads +122 the A/C is nice and cold, but at -40 it does not work at all. I just wish there was a schematic or diagram on how the wiring is laid out to make it easier for me to find the wires it came dislodged from.
 
#10 ·
The thing about this that I find truly amazing is that the temp sensor in the brake duct talks to the OD II Diagnostic System at all. I've never heard of a connection between this sensor and the Check Engine (SERVICE ENGINE SOON) light.

I agree completely that the discussion is on the correct sensor -- you crashed the car, the sensor has been problematic ever since -- because the sensor certainly does live in a location that would be exposed to a minor collision. The problem I have is that there is a relationship between the sensor and the Check Engine light. I'd be interested in the specific code that came back...
 
#11 ·
The thing about this that I find truly amazing is that the temp sensor in the brake duct talks to the OD II Diagnostic System at all. I've never heard of a connection between this sensor and the Check Engine (SERVICE ENGINE SOON) light.

Today I had the same problem loosing my lower part of my fender where this sensor is located and the SERVICE ENGINE SOON light came out.
 
#12 ·
The thing about this that I find truly amazing is that the temp sensor in the brake duct talks to the OD II Diagnostic System at all. I've never heard of a connection between this sensor and the Check Engine (SERVICE ENGINE SOON) light.

Today I had the same problem loosing my lower part of my fender where this sensor is located and the SERVICE ENGINE SOON light came out.
I still have not gotten mine fixed(long story involving insurance), but one funny thing is that during normal days it operates fine. The service engine light is still on, but as long as it does not rain, the A/C blows cold. But when it rains, I'm assuming the exposed wires get moist, the temperature reading starts bouncing around on the dash and the A/C stops cooling.
 
#13 ·
Ok guys, a new mystery.

The body shop took off the old bumper and found exposed wires, BUT on the passenger side of the front end, not the left. Also the wires are a different color than the end of the sensor probe I still have.
Needless to say this is strange because the place for the end of the sensor probe to fit into is on the drivers side, not the passenger side.

So the body shop is speculating that there might be some other electronic item that was ripped off on the passenger side as well.

Any ideas what that wire might have tied into?
 
#14 ·
There are two sensors, one in each fender liner.

The driver's side is the longer "pencil" shaped ambient temperature sensor that feeds the temp display (and apparently also interacts with the automatic climate control).

The passenger side fender liner may have a "hockey puck" shaped thermal switch for heated windshield washer jets, if so equipped. The wires are there even if the car doesn't have the thermal switch installed.
 
#26 · (Edited)
Would be nice to know your model and year because there are variations from one year to another in features, etc.
Do you have an OBC controlled by a stalk in your car?
Do you think there is any provision for temperature indicator on your dash?
I'd say if you have the sensor, your should see the temperature on the dash.
Do you have auto climate control?
 
#30 ·
Ambient air temp and washer fluid warnings

I have a 2005 325i with cold weather package (cuz' I live in Buffalo!). I recently had an accident. I now have a yellow service engine soon light (code P0070 which is the ambient air temp sensor) and a low washer fluid yellow warning light on my dash.

I replaced the ambient air temp sensor (attached to the drivers side front wheel well cover) and this did not turn off the service engine soon warning. Bummer, not Bimmer.

I also replaced the the waher fluid level sensor which is loaded into the bottom of the washer resevoir. I fiiled up the resevoir howeever, the low fluid warning is still on.

Is it possible that the obscure puck-shaped temp sensor "aparently" located on the passenger side beneath the bumper could be causing both problems?

I'd appreciate any help.
 
#31 · (Edited)
I also replaced the the waher fluid level sensor which is loaded into the bottom of the washer resevoir. I fiiled up the resevoir howeever, the low fluid warning is still on.
Quiz for you: do you know where your washer fluid container is on the passenger side of your car?
Do you know where your Expansion Tank reservoir is located on the driver's side with a coolant level sensor mounted into the bottom of this tank?
 
#33 ·
I don't think the puck sensor would have any bearing on your washer fluid level sensor.
I don't have the cold weather package, and I completely forgot there was a level sensor. Never seen my light as my res has stayed near the top for nine years. Never drive in snow.
Hook up the sensor and turn on the car and play with the float or whatever is there to sense. See if you can get it to change the dash light.
 
#34 ·
I checked today and do not have a puck sensor. I'm baffled. So, my status is:
- "SERVICE ENGINE SOON" yellow warning on dash (code is for Ambient Air Temperature Sensor circuit.
- "WASHER FLUID SYMBOL" yellow warning on dash.
- "BRAKE LINER SYMBOL" yellow warning on dash.
- "ABS" dull yellow warning on dash. It's right next to the BRAKE LINER SYMBOL.

HVAC works fine.
Washer fluid reservoir is full
Just changes front brakes including pads, rotors and sensor.
Check rear brakes and sensor (OK).
ABS works fine. ( I drive in the snow!)
My outside mirror control doesn't work. (this is the only thing not working properly.)
 
#43 ·
Ambient (outside) air temperature quick "fix"

The Ambient (or Outside) air temperature sensor is just a basic thermistor (thermally variable resistor) For cars, this type of thermistor usually has a wide range of resistance based on temperature. Typically somewhere around 10,000 Ohms to about 100 Ohms... Depending on whether it is a PTC or NTC (positive or negative) the resistance will rise or fall with increasing temperature. For this purpose we don't really care. If you want to bypass or trick the car into thinking it has a properly installed sensor you just need a resistor that is somewhere in the middle of the range (5000 Ohms)... I happened to have a 5600 ohm resistor laying around that produced a 73F reading at the dash. You can also go to your local electronics store (radioshack for me) and purchase a few 2500 Ohm resistors to "tune" the temperature reading to be somewhere in the middle for your car... Start with one resistor wired directly between the wires for the sensor. (if you still have the plug, just insert the leads into the plug) Then turn on the car and see what the temp. reading is... Then try 2 resistors wired in series and check the temp... If the reading goes the wrong way, try to wire the same 2 resistors in parallel then check the temp reading... with a few 2500 Ohm resistors you shold be able to get a temperature reading somewhere around room temperature (70f). Series Wiring is end to end like a chain... Parallel wiring is bridged like a bunch of staple in a stapler before they are used...
 
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