Help with fault code: 00256 - A/C Pressure/Temperature Sensor (G395)

[AudiNike12]

Hi. Discovered this fault code today:

08-Auto HVAC:
00256 - A/C Pressure/Temperature Sensor (G395)
004 - No Signal/Communication

AC seems to work fine though. Anyone know the symptoms of this code? Anything I can check/test in VCDS? I mean before I've to take the bumper off to check the connector and sensor visually

This showed up about a month ago along with:

19-CAN Gateway:
01044 - Control Module Incorrectly Coded

[AudiNike12]

I checked 08-Auto HVAC, MVB 54 in VCDS and all 4 blocks read 0. Which makes sense if there's no communication I guess. Why is there no signal though.

Not my picture. Just to show the blocks

[christianb5s4]

My first recommendation is to clear the codes and see if it comes back. Sometimes the car's computers will see something random that it doesn't like and create a code despite it being a one-off event. Now, if the code returns then you know there's something going on.

[AudiNike12]

I've cleared it and it does come back. Fuse and relay is fine. Guess only option is to check the connector and sensor itself no?

[christianb5s4]

In that case I'm not sure, wish I could be of more help. Did some searching and looks like an easy replacement as our C6's sensor is in the same place as the B8s and seems to have solved the codes by replacing that sensor.

https://www.audizine.com/forum/showt...ioning-to-Work

[AudiNike12]

Thanks. Yeah, looks like I'll try and replace it. Unfortunately, unless you've really tiny hands, I'll have to remove the bumper to replace it. Or at least put it in service position. It's on the side of the radiator

[AudiNike12]

Just replaced the sensor and the fault code cleared

[JohnnyB]

Just replaced the sensor and the fault code cleared

Thank you for the follow up post.


Sent from my iPhone using Tapatalk

[coop3422]

Just replaced the sensor and the fault code cleared

Old thread, but did you have to remove the bumper or put in service position to replace the sensor? My AC didn't work when I bought my S4, and the dealership recharged the system but it still didn't work, and they couldn't find any other issues to told me to spend $4k replacing the AC unit. Couple months later I get an OBDeleven and have the 00256 code. I'm probably not lucky enough for just a sensor to fix the problem, but damn worth trying.

[metanosis]

AC shut off within seconds.....no cool air.....
Research showed G395...ran vcds....Module 08-Auto HVAC No faults
Then found compressor no clutch type....solenoid valve goes faulty....compressor still good(most cases)replaced......
still no cool......

Reran VCDS....checked Module 09-Elect--00256 code!, but no code in 08-Auto HVAC
Replaced G395...still no cool.....
Check for power at G395...battery voltage.....

Also....Measuring blocks show nothing....054 block shows nothing...no title, 0.0 (no Units)....

So am guessing data not getting from G395 to wherever it goes, the J519 via LIN wire?

Wire looks good......not sure what to do next....is there a way to rule out compressor.....
have seen nothing on this...and it seems that might be easier than trying to track down electrical gremlins....
system has 100psi static pressure now....almost 20 Oz 134a....still not turning on....

[MTL4]

AC shut off within seconds.....no cool air.....
Research showed G395...ran vcds....Module 08-Auto HVAC No faults
Then found compressor no clutch type....solenoid valve goes faulty....compressor still good(most cases)replaced......
still no cool......

Reran VCDS....checked Module 09-Elect--00256 code!, but no code in 08-Auto HVAC
Replaced G395...still no cool.....
Check for power at G395...battery voltage.....

Also....Measuring blocks show nothing....054 block shows nothing...no title, 0.0 (no Units)....

So am guessing data not getting from G395 to wherever it goes, the J519 via LIN wire?

Wire looks good......not sure what to do next....is there a way to rule out compressor.....
have seen nothing on this...and it seems that might be easier than trying to track down electrical gremlins....
system has 100psi static pressure now....almost 20 Oz 134a....still not turning on....

00256 - AC Pressure/Temperature Sensor (G395) - No Signal/Communication

What year/model was the vehicle? Was this an OEM Audi sensor you installed? What part number did you use?

Here's why making sure you have the correct part number is important:
https://forums.ross-tech.com/index.p...e-9#post-34614
https://forums.ross-tech.com/index.p...e-9#post-91330