Jump to content


Photo

2009 C4 Picasso OBD2 no comms


  • Please log in to reply
8 replies to this topic

#1 Triumph Guy

Triumph Guy

    18 HDI LX

  • Members
  • PipPip
  • 62 posts
  • Gender:Male
  • Location:Halifax, West Yorkshire

Posted 21 February 2020 - 08:01 AM

I offered to fix a C4 Picasso. I plugged in my Diagbox and it didn't pick up the VIN and after it was manually inputted it soon became apparent why it didn't pick it up. It was unable ro read any of the modules. I'll be going back to diagnose the OBD2 port using my own C4GP as a known good reference. The fuse on the battery fusebox has been checked and it is fine. Does anybody know why this would happen?

The whole thing stemmed from am ABS/ESP/handbrake problem. It was taken to a garage who couldn't diagnose the problem and tried a known good used ABS pump which didn't fix the problem. The owner's son posted on the C4 Owners forum (link below) for help and being local and having Lexia/Diagbox I reached out to him.

http://c4owners.org/...opic.php?237348


2008 Citroen C4 Grand Picasso 2.0 HDi Exclusive (MA08 WCL - the daily driver and workhorse)

1972 Triumph Dolomite 1850 auto (NYE 751L - the classic)

1995 BMW E36 318i (M265 PNC - Project Bimmer)

1991 Toyota Celica GT (J481 ONB - the current project car)


#2 discv

discv

    1.8 HDI Exclusive

  • Members
  • PipPipPipPip
  • 973 posts
  • Gender:Male
  • Location:London UK

Posted 21 February 2020 - 05:23 PM

I wonder what happens if you plug in a bog standard code reader. My first guess is a problem with the onboard connector, wiring or the OBD fused power supply.

My thinking is that if the ECUs really were not working then the thing would not run at all.


C4 Grand Picasso 1.6 HDi 16V FAP/DPFS 110, -Auto (DV6 - 80kW) (C4) (DT) (2008)

 


#3 Triumph Guy

Triumph Guy

    18 HDI LX

  • Members
  • PipPip
  • 62 posts
  • Gender:Male
  • Location:Halifax, West Yorkshire

Posted 24 February 2020 - 01:01 PM

The car will start and run so there's nothing major wrong.

 

We got it recovered to a family member's driveway. I tested the live and grounds on the OBD2 port with a power problem and they're fine. I'm reading just over 2 volts on both the CAN high and CAN low pins. I connected my Diagbox and it was still the same. I tried it on my own C4GP and it picked up my VIN straight away so my Digbox is fine. It might be worth hooking up a cheap code reader to see what happens.


2008 Citroen C4 Grand Picasso 2.0 HDi Exclusive (MA08 WCL - the daily driver and workhorse)

1972 Triumph Dolomite 1850 auto (NYE 751L - the classic)

1995 BMW E36 318i (M265 PNC - Project Bimmer)

1991 Toyota Celica GT (J481 ONB - the current project car)


#4 discv

discv

    1.8 HDI Exclusive

  • Members
  • PipPipPipPip
  • 973 posts
  • Gender:Male
  • Location:London UK

Posted 24 February 2020 - 05:32 PM

I agree that to plug in a simple code reader might give you some direction.

If, for example, the code reader is able to establish a connection- that would indicate an error of VIN/RPO manual input on your Lexia. Or that there is history- a BSI swap or something.

But if the code reader sees nothing- you may have a big problem in finding the cause.

It might be worth cross checking the VIN/RPO on the Citroen Service Box site.

I would not be concerned about Diagbox pick up the VIN automatically- I've found it rarely works.


C4 Grand Picasso 1.6 HDi 16V FAP/DPFS 110, -Auto (DV6 - 80kW) (C4) (DT) (2008)

 


#5 Triumph Guy

Triumph Guy

    18 HDI LX

  • Members
  • PipPip
  • 62 posts
  • Gender:Male
  • Location:Halifax, West Yorkshire

Posted 26 February 2020 - 07:54 AM

The first time I tried Diagbox, I manaually inputted the VIN (taken from the most recent MoT certificate) and it wasn't detecting any of the modules so there was definitely a problem. The garage where it had been taken to couldn't get any error codes either.

I've found a video on YouTube giving more details on the various pins on the OBD2 port so I can do some more testing on the CAN high and CAN low pins. I'll take some measurements on my own C4GP as a reference of a known good one.


2008 Citroen C4 Grand Picasso 2.0 HDi Exclusive (MA08 WCL - the daily driver and workhorse)

1972 Triumph Dolomite 1850 auto (NYE 751L - the classic)

1995 BMW E36 318i (M265 PNC - Project Bimmer)

1991 Toyota Celica GT (J481 ONB - the current project car)


#6 Triumph Guy

Triumph Guy

    18 HDI LX

  • Members
  • PipPip
  • 62 posts
  • Gender:Male
  • Location:Halifax, West Yorkshire

Posted 27 February 2020 - 07:37 AM

I've ordered a cheap code reader on Amazon so I can try it the next time I'm out to this C4 Picasso. I also want to try it on my own C4GP for an easy way to get rid of the air suspension fault codes that keep on coming up (I did the coil spring conversion) without the hassle of using Diagbox on my laptop.


2008 Citroen C4 Grand Picasso 2.0 HDi Exclusive (MA08 WCL - the daily driver and workhorse)

1972 Triumph Dolomite 1850 auto (NYE 751L - the classic)

1995 BMW E36 318i (M265 PNC - Project Bimmer)

1991 Toyota Celica GT (J481 ONB - the current project car)


#7 discv

discv

    1.8 HDI Exclusive

  • Members
  • PipPipPipPip
  • 973 posts
  • Gender:Male
  • Location:London UK

Posted 27 February 2020 - 05:40 PM

It will be interesting to see if the cheapo reader can connect.


C4 Grand Picasso 1.6 HDi 16V FAP/DPFS 110, -Auto (DV6 - 80kW) (C4) (DT) (2008)

 


#8 Triumph Guy

Triumph Guy

    18 HDI LX

  • Members
  • PipPip
  • 62 posts
  • Gender:Male
  • Location:Halifax, West Yorkshire

Posted 27 February 2020 - 11:05 PM

I've tried the reader on my C4GP and it works.

 

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.


  • discv likes this

2008 Citroen C4 Grand Picasso 2.0 HDi Exclusive (MA08 WCL - the daily driver and workhorse)

1972 Triumph Dolomite 1850 auto (NYE 751L - the classic)

1995 BMW E36 318i (M265 PNC - Project Bimmer)

1991 Toyota Celica GT (J481 ONB - the current project car)


#9 Triumph Guy

Triumph Guy

    18 HDI LX

  • Members
  • PipPip
  • 62 posts
  • Gender:Male
  • Location:Halifax, West Yorkshire

Posted 17 March 2020 - 07:47 AM

Time for an update.

 

The multiplug connectors for the engine bay fusebox have all been cleaned up, reseated and the OBD2 socket is now in working order. Measurements have been taken and they're pretty much similar to my own C4GP so this bodes well. The readings indicate that the integrity of the CAN network has been restored. I haven't been back since recovering the C4P to it's current resting place so the work wasn't done by me. The next time I'm out to it, I'll be using my code reader and Diagbox and I'm confident that we should be able to connect to the vehicle and read the fault codes.

Some people recommend disconnecting the battery to measure the resisitance on the CAN network and others recommend waiting until the network is powered down after the ignition is switched off. I've been watching some YouTube videos and I've learnt a bit about the CAN network. At each end of the CAN network is a 120 Ohm resisitor and they're both connected in parallel to prevent "ghosting". Being connected in parallel, this halves the resistance giving 60 Ohms.

 

There will be a further update the next time I'm out there.


  • Lancelot likes this

2008 Citroen C4 Grand Picasso 2.0 HDi Exclusive (MA08 WCL - the daily driver and workhorse)

1972 Triumph Dolomite 1850 auto (NYE 751L - the classic)

1995 BMW E36 318i (M265 PNC - Project Bimmer)

1991 Toyota Celica GT (J481 ONB - the current project car)