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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 01-23-2013, 05:34 AM   #1
NukeMiller
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DIY Ambient Air Temp Sensor Troubleshooting

Read if getting any error code for Ambient Air Temperature Sensor

Step1: When SES light comes on, have it checked for free at an autozone or similar.

Step2: If code reads P0070 or 2F9A, continue reading

After receiving this error code, look under the front driver side fender to see if you see a black splash guard.
If no, you probably ran over something that ripped it off.
If yes, look to see if a little black tip is attached.

The black tip is the air temp sensor. When ripped off, you will notice that your outside temp gauge reads either -40 or +122. -40 is an open, and +122 is a short

If you do not have an outside temp indicator, then you will need to access the hidden menu on your instrument cluster.

To access, turn car off and key in the off position. Hold the trip reset button and turn the key to position 1. You should now see “test” on the left and “__1_” on the right. Start pressing the trip reset button until you reach “19”. Once you get to 19 stop pressing and watch it. It should go from “test” to toggling “L_on” and “L_off”. When it cycles to “L_on”, press and hold the trip reset button for ˝ second. Now press the trip reset button immediately after letting go from holding it until you get to test 7….once on 7, stop pressing and let it cycle. It should go from “test” to “0000”. Once “0000” is present you should see “7.0” on the right hand side. Press the trip reset button once to get to “7.1”. This will now display your outside temperature. Pretend there is a decimal point to the left of the first digit on the right. (400 = 40.0)

Here is a youtube video of some guy doing it for his battery:

When replacing the temp sensor, recommend replacing the sensor and the piece it plugs into with the wires. This allows you to eliminate problems when troubleshooting down the line if simple replacement does not work.

Once replaced, turn on your car and verify outside temp is correct. It may take a few min to calibrate, but it should read something other than -40 or +122.

If you lucky, this is the end of your solution, clear, or have someone clear your engine code and drive happy.

If you are like me, then you may need to take out the two T25 torx screws that hold your cluster in place and pull it out to access the 18 pin plug on the left side of the cluster. Pins 1 & 2 are the ones that connect to your sensor. You can check continuity with an ohm meter to verify the wire is good. Pin 1 is your ground, and Pin 2 is +5vdc (When connected into cluster. To check continuity, disconnect from cluster, take off white housing, and put lead on pin and end of wire by bumper). To verify +5vdc, plug back into cluster and check pin 2 to pin 1.

Here is the pinout with color code: http://www.bmwgm5.com/E46_IKE_Connections.htm

After all these checks you should know now where your problem lies.
If you have any questions, just ask…I had to re-route my cables because I had a break in the +5vdc.
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Old 01-23-2013, 05:45 AM   #2
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Here is a great set of pictures of what it looks like and the location: http://forums.bimmerforums.com/forum....php?t=1127615
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Old 01-30-2013, 11:52 AM   #3
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New development....Possibly, the Ambient Air Temp sensor feeds data to the Mass Air Flow sensor. I just recieved the P111F code. I am going to re-route the wires to allow the ATS to sit in its normal location...I was lazy and tried to stick the sensor behind the dash...not a good idea...LOL
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Old 06-07-2013, 12:50 AM   #4
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what happened yo?
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Old 06-12-2013, 09:12 PM   #5
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So what happens if its the dash? Does the entire thing need to get replaced or it there a fuse that needs replacing. 122 degrees constantly is causing me to rip my hair out.
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Old 07-27-2013, 06:11 PM   #6
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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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Old 11-03-2013, 05:16 PM   #7
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Ok, guys, thanks for all the pics and info. I finally found the wires for the temp sensor in front of the RF wheel. Those 2 wires are taped to nthe horn wires, and I wasn't able to find them at first because they had been ripped off right where the 2 pair separated;m the tape hid the wire ends. My wife was used to plowing through snowdrifts in her Yukon, and kept doing the same with the BMW! I was reading -40F. when I shorted the wires, the reading went to +122F. Yay! I'll get a new sensor and socket and solder 'em in.
What's the best place to get a sensor other than the dealer?
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Old 11-04-2013, 09:42 PM   #8
ddaniel1
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Bav auto has a good deal here that includes the wiring,I bought one:
http://www.ebay.com/itm/BMW-Outside-...item5658d7f9b7
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Old 11-05-2013, 11:04 AM   #9
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Temp sensor

Thanks, Daniel
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Old 11-17-2013, 04:17 PM   #10
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I fixed my sensor too but it reads +102 F when its +60 F outside. Anyone on here knows what the problem could be?
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Old 11-18-2013, 11:40 PM   #11
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Sounds like resistance in the connection or a bad sensor, I would undo and reseat the connection on the sensor a few times.
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Old 11-19-2013, 11:03 AM   #12
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Quote:
Originally Posted by NukeMiller View Post
If you are like me, then you may need to take out the two T25 torx screws that hold your cluster in place and pull it out to access the 18 pin plug on the left side of the cluster. Pins 1 & 2 are the ones that connect to your sensor. You can check continuity with an ohm meter to verify the wire is good. Pin 1 is your ground, and Pin 2 is +5vdc (When connected into cluster. To check continuity, disconnect from cluster, take off white housing, and put lead on pin and end of wire by bumper). To verify +5vdc, plug back into cluster and check pin 2 to pin 1.

After all these checks you should know now where your problem lies.
If you have any questions, just ask...I had to re-route my cables because I had a break in the +5vdc.
Unfortunately, I fall into this category as well after having my ambient temp sensor ripped out ...

Wires when not touching read +122F, which is a short. Long story short, removed dash, clipped wires 1 and 2 from plug and wired ambient sensor and replacement connector about 2 inches from plug. After that, temp reads something like +118F at first, and will slowly inch back to +122F. Still continuing to get the 2F9A code. Any ideas would be greatly appreciated but I think my problem lies in the cluster like Dillano609. I'm thinking I'll likely have to replace the cluster for the ambient temp issue unless someone can help save the day...

Oh, we also connected a variable resistor device used for diagnostic where we could manipulate the resistance, we found that the temp reading would bounce between +122F to -40F, with no readings in between no matter what we tried.

Any additional information is definitely appreciated.
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Old 11-19-2013, 11:26 AM   #13
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Ambient Temp Sensor

Well, I replaced the sensor and it all works!!
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Old 11-22-2013, 12:56 PM   #14
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Originally Posted by Martialartsblac View Post
what happened yo?
Dirty Mass Air Flow sensor. Had nothing to do with the Ambient Air Temp Sensor. Sorry for the VERY long delay on getting back here, been very busy with my work
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Old 11-25-2013, 08:39 PM   #15
KingJames
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DIY Ambient Air Temp Sensor Troubleshooting

Got a replacement ambient sensor and switched it. Temperature readings are still not accurate at all but it's different than the other sensor. No one knows what could be the problem?


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Old 11-26-2013, 05:26 AM   #16
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Originally Posted by KingJames View Post
Got a replacement ambient sensor and switched it. Temperature readings are still not accurate at all but it's different than the other sensor. No one knows what could be the problem?


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What have you tried doing and what were those results? What was the reason for having to replace the sensor?

For some reason, when I drove over mine, I was not getting the signal from my dash. This is why I did a direct connection to those pins with new wire that wasn't compromised. It is very possible that when I/we drove over these and pulled the wires that it caused in internal wire break.
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Old 11-26-2013, 10:53 AM   #17
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Originally Posted by NukeMiller View Post
What have you tried doing and what were those results? What was the reason for having to replace the sensor?

For some reason, when I drove over mine, I was not getting the signal from my dash. This is why I did a direct connection to those pins with new wire that wasn't compromised. It is very possible that when I/we drove over these and pulled the wires that it caused in internal wire break.
Nuke,

I know that your response above is not directed towards me, as we talked briefly over e-mail, but in my case I clipped wires 1 and 2 from the plug going the dash and wired ambient sensor/replacement connector about 2 inches from plug and have similar results. Mine reads about +40 F hotter than the actual ambient temp and as a result still triggers the 2F9A code (this morning it was 54 and the cluster read 96) which is similar to what KingJames is seeing. I think there may be a 3rd condition (1. replace sensor 2. replace wiring) where potentially a dash repair/replacement is needed which is where I'm at.

Hopefully this discussion continues as I'm very interested in resolving this problem and posting possible problems/solutions here.
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Old 11-26-2013, 09:06 PM   #18
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DIY Ambient Air Temp Sensor Troubleshooting

Quote:
Originally Posted by NukeMiller View Post
What have you tried doing and what were those results? What was the reason for having to replace the sensor?

For some reason, when I drove over mine, I was not getting the signal from my dash. This is why I did a direct connection to those pins with new wire that wasn't compromised. It is very possible that when I/we drove over these and pulled the wires that it caused in internal wire break.
Well my car was missing the fender wall and the ambient sensor. So I bought a new sensor and connector and connected them to the old ripped out wires. The temperature reading was in the 100s while the actual temp was 60 F. So I got another new sensor and replaced it. This time it reads around 75-90 but the outside temperature is around 40.

You think the old wires need to be replaced? I'm not an expert on wires so what kind of wire would I need to buy to replace the old ripped one? Also I replace it from the box where all those wires go to correct?


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Last edited by KingJames; 11-26-2013 at 09:07 PM.
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Old 11-28-2013, 01:30 AM   #19
NukeMiller
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Re: DIY Ambient Air Temp Sensor Troubleshooting

Yes, I would suggest replacing the wires. As stated in original post, I would replace them from the actual dash as I did. Use the same stranded 12-14 gage wire used. All I did was take the wires from the new sensor and plug kit and plugged them in directly to the back of the instrument cluster. It is still not reading the outside temp at 100% but close enough for me to stop caring. The only way to get it back to reading outside temp accurately is to run those wires all the way to the front.

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Old 11-28-2013, 01:35 AM   #20
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Re: DIY Ambient Air Temp Sensor Troubleshooting

Quote:
Originally Posted by GSX View Post
Nuke,

I know that your response above is not directed towards me, as we talked briefly over e-mail, but in my case I clipped wires 1 and 2 from the plug going the dash and wired ambient sensor/replacement connector about 2 inches from plug and have similar results. Mine reads about +40 F hotter than the actual ambient temp and as a result still triggers the 2F9A code (this morning it was 54 and the cluster read 96) which is similar to what KingJames is seeing. I think there may be a 3rd condition (1. replace sensor 2. replace wiring) where potentially a dash repair/replacement is needed which is where I'm at.

Hopefully this discussion continues as I'm very interested in resolving this problem and posting possible problems/solutions here.
Check the voltage coming from those pins. If it is not correct, then yes, you may need to replace the cluster. That my friend would suck big donkey nuts because they cost a couple hundred. I might actually take it in to a trusted shop for that kind of money to minimize easter egging.

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