4rings

The ambient temp reading in my car sometimes goes down to zero or negative numbers when it is 80+ degrees out. I took my car to an audi shop, and they replaced the G89 sensor behind the front bumper. But I still have the problem.

I STFA'd and brought up the diagnostic codes using the climate control buttons. It is indicating a 4.3 sensor code error, which is "Fresh Air Intake Duct Temperature Sensor, sporadic open". Since this sensor has already been replaced, any ideas on what could be causing this error code?

I guess I could also replace the G17 temp sensor since some other posts indicated that it is averaged with the G89 sensor to show the final ambient temperature. But the diagnostic code indicates the G89 sensor is bad, not G17?

Thanks in advance!

QCRAZY

...that sensor wasn't replaced.

You said, ".....and they replaced the G89 sensor behind the front bumper"

You then said, ".....indicating a 4.3 sensor code error, which is "Fresh Air Intake Duct Temperature Sensor, sporadic open."

Hmm?? The front bumper sensor is no where near the Fresh Air Intake Duct sensor. The sensor that you have bad is directly below the cabin/pollen filter; not at the front bumper. I guess the dealer replaced the wrong sensor...as most people do.

Luckily, the sensor you have bad is the cheaper of the two. Too bad you get to replace both.

Also to correct some of what was written. The computer does not use the average of the two sensors. It uses the lower temperature of the two sensors to try to adjust (as much as possible) for the engine heat.

4rings

OK thanks for the clarification and info. I knew I was missing something.

Swank4

is it possible to know which sensor is bad or do you have to use VAG to determine that?

Also, could a bad sensor affect engine performance (i.e. does the ECU use this temp for any of it's engine parameters)? TIA. I think my sensor is going since I get erroneous readings from the cluster.

Swank4

What's the path to the codes on VAG? I think I have a bad sensor too.

4rings

<ul><li><a href="https://www.audiworld.com/tech/int5.shtml">climate control diagnostic codes</a></li></ul>

IvanS4

I just checked and my car is displaying code 4.3 as well as giving funky low temp readings. So what is the part number for the "Fresh Air Intake Duct Temperature Sensor," located under the pollen sensor?

QCRAZY

Call your dealer for part numbers.....get both and post them so we'll know.

IvanS4

GK1 posted this a few months ago:

This is the one under the pollen filter.

It appears there is a revised part.
Old = 4A0 820 539
New = 4A0 820 539 A

The new one is about a quarter inch shorter, and light grey, whereas the stock one was black.

PITA to change, but not amazingly difficult.

---

I'm searched with the new part number and haven't found anything. All I can find is the old part #. Any suggestions?

QCRAZY

They list the old one but not the new:

http://www.worldimpex.com/