SENT vacuum sensor??

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dosdawson
Newbie
Posts: 8
Joined: Mon Jun 23, 2014 10:59 am

SENT vacuum sensor??

Post by dosdawson »

Hi
I'am after some help in decoding, what I think is a SENT vacuum sensor? I have attached two captures from a faulty sensor and the new working sensor. The vehicle is a 2020 Range rover v6 diesel. Basically there is zero information from JLR about diagnosing this sensor, I had vehicle in with brake fault on dash. There is no live data availible with pathfinder so I had no choice but to chance it and replace sensor first. Luckily it fixed it but now I want to know why? I have tried the decode function within picoscope but I cant get any data! Does anyone know how I can do this to see what faulty sensor is transmitting??
Thanks
Rob D
vacuum test2 good.psdata
(18.57 MiB) Downloaded 275 times
vacuum sensor 2 bad.psdata
(19.31 MiB) Downloaded 276 times
vacuum sensor.JPG

dosdawson
Newbie
Posts: 8
Joined: Mon Jun 23, 2014 10:59 am

Re: SENT vacuum sensor??

Post by dosdawson »

Hi
Forgot to add screenshot of sent info I got!
Attachments
sent info.png

KimAndersen
TwoWaves
TwoWaves
Posts: 246
Joined: Fri Nov 30, 2012 2:53 pm
Location: Denmark

Re: SENT vacuum sensor??

Post by KimAndersen »

Hi

Here is a link to an earlier post regarding decoding a rail pressure sensor where
Ben Martins and I describe in detail the problems that can be with the decoding of various SENT sensors.

topic22061.html

I think one of the reasons you do not see any data being decoded is because you have
too little a capture time - you have 20 mS which is very little compared to capturing
these fast SENT signals - try with 1 to 2 seconds instead.

Regards
Kim

dosdawson
Newbie
Posts: 8
Joined: Mon Jun 23, 2014 10:59 am

Re: SENT vacuum sensor??

Post by dosdawson »

Ok thanks will give that a go when I get a chance and let you known the outcome 👍

ben.martins
Pico Staff Member
Pico Staff Member
Posts: 539
Joined: Tue May 16, 2017 1:02 pm

Re: SENT vacuum sensor??

Post by ben.martins »

Hello dosdawson,

Thanks for your post here as it shows these sensors are now appearing a little more often.

Thanks also to Kim for pointing out the previous work we had already put together, I couldn't have done it without your input Kim.

Looking at your captures it looks like the tick time is different from the standard 3us. I compared the captures you have uploaded with some of my own and it looks like the captures you packets are running about 4 times slowing than the ones I have. With that in mind I changed the tick time from 3us to 12us and Pico is now decoding your packets on both fast and slow.
Different Tick Time.png
Unfortunately I can't open the bad one to compare the values of the decoded channel data but if you can upload again that would be great and we can try and spot the differences.

As Kim has already mentioned, it would be good to get a bit more time on the screen. In the original replies we have recommended between 1s/div and 2s/div and keep the sample rate high, around 10MS should be OK. This will ensure there is plenty to decode and you can even get a snap throttle in to see the changes in the data as pressure changes.

I hope this helps and happy to take a look at any other captures you may have.

Kind regards

Ben

dosdawson
Newbie
Posts: 8
Joined: Mon Jun 23, 2014 10:59 am

Re: SENT vacuum sensor??

Post by dosdawson »

Hi Ben
Thanks for taking a look i will have a go myself.
here is the capture of the Faulty sensor
Thanks
Rob D
vacuum senaro2 bad v2.psdata
(16.55 MiB) Downloaded 313 times

dosdawson
Newbie
Posts: 8
Joined: Mon Jun 23, 2014 10:59 am

Re: SENT vacuum sensor??

Post by dosdawson »

When i get a chance i will recapture a known good sensor. Unfortunatly I have not got the faulty sensor any more it went back to JLR under warranty
thanks
Rob D

ben.martins
Pico Staff Member
Pico Staff Member
Posts: 539
Joined: Tue May 16, 2017 1:02 pm

Re: SENT vacuum sensor??

Post by ben.martins »

Hi Rob,

Thanks for this. At first glance we can see that the Fast decoded data Channel 1 is different between the old and the new sensor.

In the bad sensor we have values at 1745 and 1746.

In the good sensor we now have 3238 and 3239.

A clear difference between the two!

If you are able to get some more captures then this will only help with the knowledge we gain on these sensors and how we can better diagnose them going forward.

Kind regards

Ben

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