Picasso under inflation monitoring fault and faulty ambient temperature

Hi,

A while ago the Under Inflation Monitoring Fault indicator appeared on the C3 Picasso dash display. I followed the handbook process to clear it and all was well... for a while. The fault reappeared and I was able to clear it using the handbook procedure. Now, however, the error appears every time the ignition is switched on. 
Additionally the ambient temperature display no longer works. It went through a period of showing wildly inaccurate readings on switch on but then settling down after a short period. 
Can these 2 issues be linked via a faulty BSI unit? I am assuming that the C3 Picasso uses the standard BSI unit as I can't find a definitive answer.

I have taken the car in to the local garage and they have confirmed that they can see an ambient temp reading from the sensor on their test equipment even though it is not displayed. They had no luck with the under inflation monitoring fault as they couldn't get their kit to interrogate the system.

Is it likely that these issues are both caused by a BSI problem and is it possible they could be cleared by the reset procedure described on this site?

The Citroen garage will be treating them as 2 separate faults so there will be 2 x £89 investigation charges as a starter. 

Has anyone any experience of similar issues on a C3 Picasso?

Thanks in advance for any advice.

It's very strange that the diagnostic machine would show a correct temp reading but the display doesn't. I am not familiar with the under inflation warning system.

Does the car have an after market radio installed?

Ozvtr wrote: ↑Sat Feb 13, 2021 10:01 pm It's very strange that the diagnostic machine would show a correct temp reading but the display doesn't. I am not familiar with the under inflation warning system.

Does the car have an after market radio installed?

Just a quick not on how the under-inflation system works. The system (presumably BSI) is initiallised whilst driving so that it knows how fast each wheel rotates compared with each other by taking readings from the abs sensors. When one of the tyres deflates slightly the rolling radius decreases and the wheel has to rotate faster. and flags up a warning. A tyre has to lose ~7-8psi before the alarm goes as the system has to allow for differences between the left and right side speeds on cornering and the fact that front wheels cover slightly more ground than rear wheels. It only works when the car is moving and is only any use at detecting relatively slow deflation, so it will not react to a burst tyre, and you will not get an alarm if a tyre has deflated overnight. Although it should be possible, it doesn't actually tell you which tyre in under inflated. It will also not tell you when all tyres are under-pressure like happened on my C4 Picasso when I checked them after several weeks immobile due to lockdown.

Hi both,

Thanks for the replies. The system has the standard radio installed.
I'm slightly perplexed how the fault is only showing as an inflation monitor fault if the system uses the abs sensors. Surely the ABS should be flagging an issue as well/instead?
Does this mean that the car can see the abs sensors OK but then misinterpreting the rotational values or could it be that the sensor is seen but is giving an incorrect rotational reading?

Thanks,

From what little I know about Citroen's tyre monitoring system, it uses pressure transmitters in the tyres and is part of the valve stem.

Without scanning the error code, it could be anything. Receiver module, or one of the transmitters in the wheels?

My guess would be one of the batteries in the transmitters going flat, seeing as it is getting worse and worse. But that's just a guess.

As far as the temp display goes, what does it display? Nothing, dashes, wrong numbers, a picture of an elephant (just kidding)?

You should be entitled to get Citroen (or Peugeot...yes Peugeot!) to scan your car (for a price) and give you a detailed result of that scan. You should then be able to take that to a mechanic of your choice and have repairs effected. However some dealers can be @$$ holes and refuse that request unless you are going to get the repairs done there. I do not know how the law stands on that.

Ozvtr wrote: ↑Tue Feb 16, 2021 10:17 pm From what little I know about Citroen's tyre monitoring system, it uses pressure transmitters in the tyres and is part of the valve stem.

Without scanning the error code, it could be anything. Receiver module, or one of the transmitters in the wheels?

My guess would be one of the batteries in the transmitters going flat, seeing as it is getting worse and worse. But that's just a guess.

As far as the temp display goes, what does it display? Nothing, dashes, wrong numbers, a picture of an elephant (just kidding)?

You should be entitled to get Citroen (or Peugeot...yes Peugeot!) to scan your car (for a price) and give you a detailed result of that scan. You should then be able to take that to a mechanic of your choice and have repairs effected. However some dealers can be @$$ holes and refuse that request unless you are going to get the repairs done there. I do not know how the law stands on that.

The earlier cars in the 2000s used to use individual pressure sensors. These had metal inflation tubes and used to snap because of metal issues. They also meant that you couldn't change the wheel positions as the sensors had to be programmed. The newer system cam in in the early 2010s and is as I described in the post above. Needs no harware so minimal cost to comply with the then current regulations.

Milkie can you provide us with the VIN of this car please?

Hi, sorry for delay in responding.

The fault is resolved, hopefully.

Apparently it was the ambient air sensor fault that caused the issue with the tyre pressure monitoring system. They said the air temp is used to calculate the tyre pressures. The garage changed the sensor and it cleared both issues. Not as cheap a resolution as I would have hoped... £240.

I thought this was strange because the TPMS fault was happening intermittently for a while before the ambient air temperature started to noticeably act up.

On the plus side the garage advised that there was a recall for the catalytic converter which was changed.

Thanks for your replies.

Milkie wrote: ↑Wed Mar 10, 2021 2:19 pm Hi, sorry for delay in responding.

The fault is resolved, hopefully.

Apparently it was the ambient air sensor fault that caused the issue with the tyre pressure monitoring system. They said the air temp is used to calculate the tyre pressures. The garage changed the sensor and it cleared both issues. Not as cheap a resolution as I would have hoped... £240.

I thought this was strange because the TPMS fault was happening intermittently for a while before the ambient air temperature started to noticeably act up.

On the plus side the garage advised that there was a recall for the catalytic converter which was changed.

Thanks for your replies.

This seems odd. The system does not calculate the pressure, it only compares rolling radii. The system will not give any warning if all of the tyre pressures fall at the same rate. Sounds like an odd coincidence to me. There used to be a thread on another forum with a title like 'a Citroen agent told me' and this seems to be a suitable candidate for that.