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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > Fault code for AUC Sensor - A6CF



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      05-29-2018, 08:37 AM   #1
e90yyc
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Fault code for AUC Sensor - A6CF

I've replaced my sensor with one from a scrapyard and am still getting this code... Yes, I've cleared it many times and it keeps popping up.

Has anyone else had theirs fail? I can't find many posts about it (probably because it's insignificant and nobody cares ha), so I'm trying to figure out what the likelihood is that it's the sensor versus wiring or something else.

Clearing codes and disconnecting AUC sensor will also throw a A6CF code, so it seems the fault is quite general and does not refer to the function of the AUC sensor itself.

If there is any way for me to test it with a multimeter too, I'd give that a try. I'll probably start by checking the actual harness for voltage, but I'm not sure what is normal here.
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      07-23-2018, 06:28 PM   #2
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Did you ever figure this out? I came across your post while searching for info on the AUC sensor, my AC isnt working and I have two codes I think are related.

The first is the same one you have re the AUC, the second is DRUCK_SENSOR (9C5E), which translates to pressure sensor. I am hoping this refers to the AC pressure sensor, which I have a feeling it does since I get infinite resistance across all the pins of the pressure sensor, but have 13.9V, 5V, and ground at the harness for the pressure sensor.

Do you know if the AUC sensor will prevent the AC compressor from engaging? I have the pressure sensor on the way, and just want my AC to work so if I need to get the AUC on the way I will.
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      07-23-2018, 07:58 PM   #3
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Quote:
Originally Posted by jarad35 View Post
...Do you know if the AUC sensor will prevent the AC compressor from engaging? I have the pressure sensor on the way, and just want my AC to work so if I need to get the AUC on the way I will.
The AUC function is to detect pollutants in the ambient air when A/C is using outside air (as opposed to recirculating inside air). If it detects pollutants, it causes the recirculation flap to go to recirculate mode, but it does NOT shut down compressor function. A non-functioning Refrigerant Pressure Sensor WILL prevent compressor function however, so you will have everything you need to restore refrigeration circuit function when the new Pressure Sensor arrives (assuming you have a vacuum pump, refrigerant, etc. ;-).

Note the 2nd post in this thread:
https://www.e90post.com/forums/showthread.php?t=1085988

George
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      07-23-2018, 08:24 PM   #4
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I did get this figured out. Had bad sensors. Got a good one and all is well now.

As George mentioned this won’t prevent anything other than AUC-specific functions from working.
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      07-23-2018, 10:56 PM   #5
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Quote:
Originally Posted by e90yyc View Post
I've replaced my sensor with one from a scrapyard and am still getting this code...disconnecting AUC sensor will also throw a A6CF code, so it seems the fault is quite general and does not refer to the function of the AUC sensor itself.
Quote:
Originally Posted by jarad35 View Post
...I have two codes I think are related. The first is the same one you have re the AUC, the second is DRUCK_SENSOR (9C5E), which translates to pressure sensor.
Just to clarify: Since BOTH the AUC and Refrigerant Pressure Sensors (along with the Compressor Control Valve are connected to the JBE which is in turn connected to the IHKA, I would presume that either code (A6CF or 9C5E) was found by connecting to the JBE as opposed to the IHKA, or else found using Functional Jobs (assuming you are using INPA) and shown as being saved in JBE error memory?

Thanks,
George
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      07-23-2018, 11:13 PM   #6
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A6CF was on JBE module, yes.
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      07-24-2018, 10:58 PM   #7
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Installed a new AC pressure sensor, haven't charged it yet, but still getting 0 bar reading in INPA. It doesn't fluctuate at all, which seems very strange to me. It's just a flat 0 bar, but I have signal and reference voltage to the harness, which makes me think the connection is fine.

Could this be the IHKA or JBE not properly interpreting the signal? I am thinking I need to test continuity from the sensor harness to the JBE, but I'm getting the correct voltages at the harness. Is there anything else I should be looking at here to try to fix this?

Last edited by jarad35; 07-25-2018 at 02:06 PM..
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      07-25-2018, 08:00 PM   #8
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For inpa reconnected, I still have a 9c5e error with the new pressure sensor. Found the pinouts for the JBE, I am not getting continuity between the pressure sensor earth, and pressure sensor signal or activation pins on the connection. I'm assuming this is a problem, since these must need to connect to ground.

Does anyone have any advice on where to go from here?

Last edited by jarad35; 07-25-2018 at 08:24 PM..
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      07-25-2018, 09:20 PM   #9
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Ok, so after some more digging around I noticed my voltage with the engine running is 14.9-15v (measured with a fluke from the + terminal under the hood to ground). I think this is too high, but I don't know if the ECU can request this much voltage. I'm afraid this is the core of the problem, and the over voltage is causing a problem with the AC sensor, or worse it's toasted my JBE.

How high can the alternator voltage safely go on an e93?. I can't get the ecu to load in inpa, I think I have the wrong ipo file. It tells me it's looking for zbel87_2, and I only have it without the _2.

Last edited by jarad35; 07-25-2018 at 10:32 PM..
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      05-18-2019, 05:51 AM   #10
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AUC sensor

I have the same fault , is this a relatively easy job to do .?
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      05-20-2019, 12:23 PM   #11
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Quote:
Originally Posted by BillyOnions View Post
I have the same fault , is this a relatively easy job to do .?
Super easy. Literally disconnect the harness and twist the old one out. Installation is the reverse of removal.
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