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BMW External Air Temperature Sensor (OBC) -40, -22, etc. E39, E36, etc.

March 2, 2011

This answer is applicable for many BMWs in addition to the one listed below.

Q
car year: 2002
car model: 525i
After a snowstorm drive my sensor in the dash reads -40 all the time. What could be wrong? i wonder if it’s become disconnected. Where do I find the outside sensor to look?

A
You likely either have a faulty exterior temperature sensor, the sensor has come unplugged or the sensor is missing altogether.  If the sensor is missing, it would not be uncommon for the harness plug to be ripped from the vehicle’s wiring as well.  We do carry all of the various model temperature sensors and we have plug repair kits for some of them.

See the Winter 2008 issue of our Fast Times newsletter for additional info on the external temperature sensors and mounting locations for most BMW models:
BMW

External temp sensor – for E39 (5-series 97-03) and others:
(see below for additional chassis information, E36, etc.)

BMW

External temp sensor plug repair kit for E39 & others:
BMW

E36 chassis (3-series 92-98):
On the E36 chassis, the sensor is located in the passenger side brake cooling duct. You can see it projecting into the duct, by looking into the duct from the front (assuming it has not been knocked out). To replace the sensor, you must access it by removing the under bumper splash shields. See the link above for the Winter 2007/2008 Fast Times, which shows a photo of the location.

E36 external temp sensor
BMW
E36 external temp sensor harness repair plug kit

BMW

4 Comments
  1. Does E36 320i have an Exterior Temp sensor. If the answer is yes, where is it located. If you have pictures – please provide.

    • We’re not sure how all of the Euro (non-US) models are optioned. However, if the vehicle has an external temp function on the OBC or in combination with a digital clock, it will indeed have an external temperature sensor. On the E36 chassis, the sensor is located in the passenger side brake cooling duct. You can see it projecting into the duct, by looking into the duct from the front (assuming it has not been knocked out). To replace the sensor, you must access it by removing the under bumper splash shields.

      The Winter 2007/2008 Fast Times has an article on replacing the external temperature sensors and shows the locations on common 3 and 5 series BMW models.

      Click HERE for Winter 2007/2008 Fast Times

      Click HERE for E36 external temp sensor

      Click HERE for E36 external temp sensor harness repair plug kit

  2. Duane permalink

    Having the same problem except mine is an 1989 735i displaying -35 f

    • Otto permalink

      We would say that your external temp sensor is faulty or missing. The -35 temp reading is another common default. On the E34 5-series(5-series 89-96) and E32 7-series (7-series 88-94) the temp sensor is mounted behind the small grill insert, just inboard of the fog light. Various model years can be on either the passenger or driver side. Simply remove the small grill/cover and you can access the sensor, right next to the fog light.

      Click HERE for E34 and E34 External Temperature Sensor

      Click HERE for temps sensor plug repair kit

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