2009 C4 Picasso 1.6HDi CAN bus issue

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Triumph Guy
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2009 C4 Picasso 1.6HDi CAN bus issue

Post by Triumph Guy »

I reached out to somebody whose mother is having problems with her C4 Picasso. It has ABS, ESP and handbrake problems. The local garage was unable to pull any fault codes. They tried a known good secondhand ABS pump but that didn't fix the problem. An appeal was made on the C4 Owners forum (I post on there under this moniker) and being local I offered to help because I have Lexia/Diagbox. I connected it up but it couldn't find the VIN. There was condensation in the vital spot on the windscreen so the paperwork had to be retrieved. Once the VIN was obtained it was soon apparent that Diagbox was unable to read the VIN because it didn't pick up any of the ECUs which is why the garage was unable to read any fault codes. The engine starts and runs.

Does anybody know what could cause a lack of communication at the OBD2 socket? I thought I'd register and post on here so see if anyone would know. This is the thread in question on the C4 Owners forum.
http://c4owners.org/plugins/forum/forum ... 37348.last
My first thought is to take measurements on the pins and compare them with a known good on my own C4GP.

The car in question is a 2009 C4 Picasso VTR+ with the 1.6HDi and the EGS transmission.

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citroenguy
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Re: 2009 C4 Picasso 1.6HDi CAN bus issue

Post by citroenguy »

Have you checked the power feed in obd contact? and its fuse!
https://pinoutguide.com/CarElectronics/ ... nout.shtml

Triumph Guy
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Re: 2009 C4 Picasso 1.6HDi CAN bus issue

Post by Triumph Guy »

Yes we checked the fuse. It is the one located in the battery fusebox. The next thing will be to check for powers, grounds and the can bus signal.

Triumph Guy
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Re: 2009 C4 Picasso 1.6HDi CAN bus issue

Post by Triumph Guy »

We got the car recovered to a family member's driveway. I tested the live and earths with a power probe and they're fine. I'm reading voltage at CAN high and CAN low (just over 2 volts). I tried my Diagbox and it still isn't communicating. I tried it on my own C4GP and it picked up the VIN so my Diagbox is working. The next plan is to trace the wires to see if there are any problems.
Last edited by Triumph Guy on 26 Feb 2020, 13:55, edited 1 time in total.

Triumph Guy
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Joined: 20 Feb 2020, 08:39

Re: 2009 C4 Picasso 1.6HDi CAN bus issue

Post by Triumph Guy »

I found a video on YouTube which gave some more detail on the CAN high and CAN low pins. I'm gonna take some measurements on my own C4GP so that I have a known good reference.

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citroenguy
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Re: 2009 C4 Picasso 1.6HDi CAN bus issue

Post by citroenguy »

Here is som good stuff on CANBUS


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myglaren
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Re: 2009 C4 Picasso 1.6HDi CAN bus issue

Post by myglaren »

Something wrong with the above links, only one playable:



The other has managed to acquire a VIN in it's code, rendering it void.

Extracting that gives



This is playable if you copy and paste the code V F3s0uZ7ok0
Paste into the YouTube search box and then remove the space between the V & the F.

Triumph Guy
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Re: 2009 C4 Picasso 1.6HDi CAN bus issue

Post by Triumph Guy »

I've seen a few Diagnose Dan videos so I'll check them out. He seems to succeed where others have failed. Somebody on another Citroen forum suggested using a cheap code reader so I've ordered one on Amazon. I also want a quick and easy way to clear the rear air suspension fault codes that keep on coming up on my own C4GP (I did the coil spring conversion) without the hassle of using Diagbox on my laptop.

Triumph Guy
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Joined: 20 Feb 2020, 08:39

Re: 2009 C4 Picasso 1.6HDi CAN bus issue

Post by Triumph Guy »

I've got the cheap code reader and it works on my C4GP

I've done some readings on the OBD2 port on my C4GP

Pins 4 & 5 are the chassis and signal grounds respectively.
Pin 16 is the permanent 12v live.
Pin 6 (CAN high) measures 2.66 volts (should be 2.5-3.5 volts)
Pin 14 (CAN low) measures 2.35 volts (should be 1.5-2.5 volts)
I also did a resistance measurement across pins 6 & 14 and I got 60.9 Ohms (it should be about 60 Ohms and the battery MUST be disconnected).

This gives us a reference for a known good OBD2 socket.