F05E - Absence of communication with the tyre under inflation detection ECU - Citroen C6 - C6

Symptoms: all of a sudden the tyre inflation sensors went from green “All good” to blinking orange on the screen.

When we parked the car, the sensors were working. I took out something from the boot, lifting the spare wheel cover. When started the car again, the little car on the screen had blinking orange tires instead of green ones. I don´t remember touching ANYTHING but the wheel cover, so no idea what triggered the error.

Initially we thought is just a hiccup. Visually inspected the tires and all seemed good, so we drove home. We thought it may need some time to recalibrate so we haven´t put to much thought to it. A few days later the error was still there, with an additional message about being unable to communicate with the tire inflation sensors.

We stopped at our mechanic to run a quick diagnostic where he identified the F05E error (and some others seemingly unrelated to this issue like Cd charger not communicating*). The errors were deleted but they re-appeared at the follow up scan immediately. So after the tire pressure was checked and all were fine, we agreed to leave it as is and come back at a later date to sort out this problem.

I started digging in order to try to figure out what could be the cause. Of course I started my “investigation” on various C6 groups and forums, but haven’t got to much about the F05E error. In meantime our mechanic looked up in his database, and he said no worries, he has the whole documentation, wiring scheme, so sooner or later we will figure out what could be the problem. While we were chatting with him, I found this website, mentioning the error and some generic “how to try to diagnose” the car errors…

Mind you 😀 we are green as a healthy spring leaf when it comes to fixing and diagnosing cars so any info was helpful 😀 Anybody into fixing cars probably is laughing at us now, but I was happy to find a “todo” list, and things to try before giving the key of the car to the mechanic…

So here is the to do list:

put the contact on connect the diagnostic tool and delete the errors (done)
do a quick and short test run to see if the errors are back. If one or another error is not back, problem is solved. If it´s back, go to step 3. (done)
check the fuses with a multimeter if you find broken ones, change them and go back to step 1. (oh we can do that!)
if the fuses are ok, and the error is still there, check the battery to be ~12V (when stoppeed) and ~14V with the engine running. Check the tension on the alternator as well. (we can do that as well!)
check the wirings, that there is no loose wire, or there is a short circuit and clean the component contacts well – check relays to work (umm… what wire exactly? there is a ton of wires in this car :D) – Not us!
pretty much means to go to a shop that will check the wiring diagrams and related components for failures 😀 Not us!

First thing was to check the owners manual to find the particular fuse boxes. This one was on the left side, behind the small glove box.

I tried to make a photo, but… I have to go back to make a better one. You can’t see the Box B on this picture.

The G29 5A fuse was indeed blown…

It was quite difficult to change this fuse, due to the lack of space… but we managed. After the first start, the “no communication” error was not showing, however I think the tire sensors will need a short drive in order to start working again. Will see tomorrow.

As a fun fact:

*in newer manuals, the G29 error and fuse refers to the Charger for 6CD’s too. In my original manual, there is no word about the cd charger being affected. However in the diagnostics, we also had F088- No communication with the CD charger error present.