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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, 06:34 AM   #1
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Join Date: Apr 2010
Location: Phoenix, AZ
Posts: 100
My Ride: 2005 325i
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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