Faulty sensor, but usually it goes the other way (mine read -48F for the longest time)

 

For the past week my car has been showing some strange behavior... The outside temperature gauge starts off normal, but then after I'm driving for about 20 minutes, it starts climbing rapidly (about 1 degree per minute) My commute from work to home isnt very long so the highest I've seen it go is 103 F, when the actual outside temp is around 70 F.
...do you think this is a faulty sensor or something worse I should check out?

Take a look under the front bumper, passenger side. I believe the sensor resides there. See if it is loose or hanging down. There are some old discussions about the temp sensor and the car acting weird if it gets knocked on a curb or otherwise.
Regards,
Jerry

 

Thats where it is, tucked into its own nacelle under the car in front of the passenger front wheel.

 

As stated above, I would check under the passenger side front bumper to see if everything is intact. If so, according to the Dinan CAI instructions, if the temp sensor becomes disconnected, the circuit needs to be reset as follows: "Short the 2 ambient air temp sensor wires together (you can use an unfolded paperclip to 'back probe' the sensor); turn the ignition key to the run position; remove the short. The OBC should now give the accurate outside temp." Might be worth a try.

 

Back probe?

If so, according to the Dinan CAI instructions, if the temp sensor becomes disconnected, the circuit needs to be reset as follows: "Short the 2 ambient air temp sensor wires together (you can use an unfolded paperclip to 'back probe' the sensor); turn the ignition key to the run position; remove the short. The OBC should now give the accurate outside temp."

Sorry for bringing up an old thread...
ECB indicated that you can reset a new Ambient Sensor by "Back Probing" the sensor with a paper clip. What does this mean?

2nd question... does the Auto Climate Control function if the Ambient Temp Sensor is not functioning? I just replaced the Final Stage Resistor and Ambient Temp Sensor. Now I have a -40 reading and the Auto Climate Control is not functioning. They must be related...

Thanks!

Driven

 

I couldn't really get "under" the front lip to see the sensor but I used my hand to feel it... I just tried wiggling it a bit and making sure it was clipped in properly.. It felt like the thing was a bit loose and very rough as if it was scraped by rocks... that plastic shield under the front bumper was still intact so I can only assume the malfunction is due to debris, water, or just the vibrations from going over so many potholes in the city.

Seems to be working better now but I'll have to drive around more to see if that issue comes up again.

 

Honestly, I don't know. I just copied that from the Dinan CAI install instructions. With the paperclip, it almost seems you're supposed to short the circuit. I'll look again at the Dinan instructions.

 

+1

Thank you!

 

Here are the Dinan CAI instructions which include temp sensor "re-connection" at #58 in the instructions.
http://www.m5board.com/vbulletin/showpost.php?p=1070128&postcount=5

 

What's the P/N for ordering a new Temp Sensor? The jiggling didn't seem to work all that well and the temp still varies a lot....

Maybe I should try some heat shielding or something since other threads I have been reading mention that in really hot weather the thing malfunctions due to radiant heat from the road / other traffic / engine bay.

 

What's the P/N for ordering a new Temp Sensor? The jiggling didn't seem to work all that well and the temp still varies a lot....

Maybe I should try some heat shielding or something since other threads I have been reading mention that in really hot weather the thing malfunctions due to radiant heat from the road / other traffic / engine bay.

It's sorta pointless to sheild it, either way, It's more of a heat index gauge than a temp gauge in my experience.

 

Seems to work pretty well for me ... always within 2 degrees of what it is outside.

And, there is a heat shield (heavy aluminum foil) inside to shield from engine heat.

 

Seems to work pretty well for me ... always within 2 degrees of what it is outside.

And, there is a heat shield (heavy aluminum foil) inside to shield from engine heat.

The heat sheilding from the engine is sorta pointless, as most of the heat that distorts it's readings comes from the Tarmac.

 

Have the same issue with mine, however I think the bogus readings started after I took the car to the dealer. I guess they had to remove the front bumper to replace my electric fan and messed up the sensor somehow. I took the car back but the dealer couldn't reproduce the problem so they didn't do anything about it and the car just got into the CPO warranty. However, it is documented in their system and I have taken several pictures with the bogus readings. The last one was reading 113 degrees and it was only 95.

Does anyone know what the cost of the sensor is with or without labor?

 

I just replaced my sensor as I was getting temperature in the 30's when it is in the 80's out and it still is messed up. Any clue what to look for next?

 

Bump? no idea what the next thing I should look at?

 

I replaced the plastic part that the sensor resides in, keeping the original sensor, and it took a few days before the sensor read correctly. Not sure why, but it would start out at a really low temp (sometimes -40 but not always) and slowly rise. You may also want to double check that the connection is pressed all the way home.

 

Thanks,
sounds like that is the next thing to do. No idea what that all connects to as will have to get under the car and see how that is in there. Was it that hard to replace? I am sure there was nothing then wrong with my current sensor then.

 

I just ordered another one and it now works.

 

It may be a **** wire. The sensor on my wagon hadn't work since I bought it. I replaced the sensor and the plug, still nothing. I just put an M5 bumper on it last week and found a cut wire all the way up near a bundle of wires. I just hand't gone far enough up the stream to find the damage. After soldering in new wire, everything works perfect.

You may want to pull your bumper cover and check the wiring up stream a bit.......

 

Before I dove in I realized the part I ordered was from some no name place as I just googled the part on the internet and figured I would spend about $30 or so on another one before I looked at anything else and to my surprise all is fine now. I learned my lesson on buying parts now.

 

My external temp just began reading high by 10-12 degrees this weekend... oil and coolant temps in normal ranges. Have not hit or bumped anything - is there a means to test the sensor --- can this be a symptom of something worse (with motor temps)?

 

My external temp just began reading high by 10-12 degrees this weekend... oil and coolant temps in normal ranges. Have not hit or bumped anything - is there a means to test the sensor --- can this be a symptom of something worse (with motor temps)?

Ok - replaced with brand new factory sensor...still seeing a reading of 5-6 degrees above ambient (no evident damage to the mounting plate or wiring harness). Anyone seen anything similar?

 

Mines also read low by quite some margin. Aircon seized to function because of this reading. Just bought a FEBI replacement. Fitted in less than 2 minutes. Job done. Aircon cold. Happy bunny.