Outside Temp Sensor Replacement
 

I've been searching all over, but can't find a good set of instructions for replacing the outside ambient temperature sensor on an M-Sport. I've looked at the TIS and it shows the standard/sport bumper needs to be removed, but I can't find instructions for the M-Sport. Can't fathom why BMW would place the sensor in a position that requires the bumper panel to be removed.

On E38', E39's and many, many others its in a position that you're able to just lay on the ground, reach up, pull out, disconnect and replace. But no, on the E70 it says you have to remove the bumper panel first.

Can someone confirm that is the case and where is this sensor physically located? Then if someone knows how to remove the M-Sport bumper panel I would greatly appreciate the advice!

I thought my sensor died when suddenly my temp read 28°F. It turned out that I just plugged the air duct where the sensor is full of 28° snow.

I think the sensor enters from the right side of the air duct that goes from the grill to the brakes on the left side of the car; you should be able to see when you remove the air stream panel below the bumper, hopefully forward of the aluminum platre.

I like you never found the step by step but at least I found the part on realoem so I could figure out where it was.

I actually found it inside the lower grill. I can reach through the open hood behind the bumper down to the sensor itself, but it is mounted tip down from inside the bumper housing so the only choice is bumper panel removal! Geeze! Thanks BMW! I had thought a windshield repair person drilling into the lower portion of my windshield where the heated winshield wires are located. But after having the windshield replaced today I still have the same problem, outside temp reading 122* so next is the sensor itself. Just so happened the temp reading error and corresponding CEL (which is stupid if you ask me) happened at the same time as the windshield repair too.

I would trace wiring. The sensor will read max or min if open or short. I think it's pegged high from an open circuit .


Sent from my iPhone using Tapatalk Pro

It actually crawls up over about 20 minutes of driving (from cold) and then pegs at 122*. While I have the bumper off I'm planning to trace it as best I can but, hopefully it's not a problem there. Do you happen to know the path the wiring takes? Since the sensor is on the left side of the lower grill I'm guessing it would go into the left fender and back towards a loom or the firewall. I replaced my expansion tank a couple of months ago, so I am hoping it didn't somehow get pinched and damaged over time from that.

If it wonders around it actually sounds more like it got loose and is too close to something hot. Does it seem close to ambient at cold start?

To test my theory, take some "canned air" and spray it upside down into the port where you can get the spray to vaporize close to the sensor.

It's important there is no air path from the hot radiator to the sensor. Maybe stuff some foam or insulation to make sure there is no hear soak from the radiator output.

Case in point: I've seen readings 40°F higher then ambient on my M54 when not moving and hot air from radiator works into the duct.

Is it possible you are just getting a path of hot air where it shouldn't be?

I never had to trace the wiring becuase my problem was a plug of snow that melted away


Sent from my iPhone using Tapatalk Pro

wasnt it -40 on the E39 m5 when the sensor got hit by a curb or parking stop?



not sure what the telltale temp is on the E70....

It's like -40 or +122 if short v open but I can't remember which way.

My Spidey senses are saying the sensor is reporting the correct temp it's experiencing and there is an inadvertent path of hot air heating maybe the outside of the duct/sensor and maybe conducting heat through the sensor to the tip

R134a which is the common spray used in "keyboard cleaner" canned air evaporates at -15F works great for testing sensors. Spray some liquid freon from a canned air on the sensor when it's reporting hot to confirm it's reading hot because it is. Then resolve the source.

FYI, if you need to replace a valve on a pipe that you don't have a practical shut off, one can of R134 poured into the pipe inside a short piece of pipe installation will freeze a 1/2 or 3/4" pipe solid for about half an hour so you can remove a part of the pipe down stream to repair or replace a valve.

Beware; no warning when it thaws it goes from zero to 100% in less than a second!

I put my oven thermometer inside the frozen cuff to monitor the temp to make sure it was frozen and have some warning.

I made a jig for R134a delivery from a needle type shop air blast valve. (plastic handle one of course). Then I can use $5 can of R134a not the $20-30 can that comes in the pipe freeze kit.

I find it humorous that the world is all freaked out about DIY venting their R134a but the "canned air" and pipe freeze kits use the identical chemical.