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C4 Picasso ECU/ABS/CANBus fault |
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TriumphGuy
 
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  Member No: #47272
Joined: Jan 13 2017Location: Halifax, West Yorkshire |
Not a problem really. A resistance test will be done as well on mine. It would make for a good video for my YouTube channel. Once I've done the readings, I'll post them up on here and we'll have a known good reference. |
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TriumphGuy
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Member No: #47272
Joined: Jan 13 2017Location: Halifax, West Yorkshire |
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. |
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rusky
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   Member No: #27768
Joined: Oct 13 2012Location: Hove |
At least it's not just me that has the issue of the clock resetting when diagbox scans the ECUs! |
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TriumphGuy
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Member No: #47272
Joined: Jan 13 2017Location: Halifax, West Yorkshire |
I found another video by the UK YouTuber "Simply Diagnostics" which explains CANbus in a little more detail. - Click Here - |
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TriumphGuy
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Member No: #47272
Joined: Jan 13 2017Location: Halifax, West Yorkshire |
After watching the previously mentioned YouTube videos I understand the CAN network a bit better. There are 2 120 Ohm resistors (one at each end of the network) connected in parallel which means the overall resistance is halved and you end up with 60 Ohms. The resisitors are put there to prevent "ghosting" on the network. With votage readings and resistance within spec, we will know that the CAN network is intact. With an oscilloscope connected to the CAN high & CAN low, the traces on the screen should mirror each other. With my own C4GP a known good reference can be obtained to compare with the C4P. |
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kbg2020
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  Member No: #55516
Joined: Jan 30 2020Location: Manchester |
An update from me (OP). Thanks for posts to this thread since TG helped me move the C4-P to my sister's drive on 22/Feb. I have been away with work but got back onto the electrics/wiring yesterday. So, yesterday (Fri 6/3) i did the following; Took out the starter battery (it had dropped to 70% since we moved the car) and put it on overnight charge. Then i went through the fuses under the bonnet; in particular the main engine compartment fusebox and the fuses on the battery. Removed, cleaned and reinstated a number of fuses - those that might be relevant. Replaced fuse F7 on over-battery fuses (5A ESP ECU) even though existing incumbent fuse seemed OK. Removed wiring loom connector blocks in main engine compartment fusebox, cleaned and reseated them. Looked for wiring breakages on wiring looms where easily accessible but nothing significant of note other than some wiring that has obviously been repaired in past by a previous owner/garage - as noted above by TG). Then today (Sat 7/3), 24 hours later I have the reconnected fully re-charged battery back in the car, switched on ignition, left for 2 minutes then started engine. Car starts up smooth, with NO faults on the dashboard. Managed to drive in reverse and forward a few times the handful of meters up and down the 8m drive and left engine running in neutral for ~10 minutes. No faults on screen. Footbrake not working; obviously brakes need bleeding. I am thinking the next step is to re-connect Diagbox and/or cheap code reader and see if we have any improvement in diagnostics comms. TG I will be in touch by phone or PM. Cheers. |
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TriumphGuy
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Member No: #47272
Joined: Jan 13 2017Location: Halifax, West Yorkshire |
This sounds really promising. The brakes will need bleeding because the ABS pump was swapped out. If you can, top up the brake reservoir and wedge the brake pedal down (a piece of wood should do the job) to help get some of the air out. They will still need to be bled. Voltage and resistance tests on the CAN high and CAN low pins will determine if the CAN network has been restored to full working order. After that, I'd like to try the cheap code reader and it that works we can hook up Diagbox. Hopefully, the fault codes can be cleared and they won't come back. The lack of error messages on the display is a good sign. | ||||
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kbg2020
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Member No: #55516
Joined: Jan 30 2020Location: Manchester |
Sunday 15/3 Update: As mentioned, I am only getting to the subject-C4P at my sister’s in Calderdale at weekends (from my home in Manchester) due to weekday work commitments etc. My mum now has a substitute car. I am hoping to get this C4P diagnosed and back on the road before its May MOT anniversary. A big thanks TG for your research and for highlighting your own C4GP reference OBD2 pin measurements. I watched the 2 x YouTube videos and dived in today on the C4P with my DMM. Results as follows: Got to the car and tested battery voltage at 12.51V Key-on (ignition live) but engine off: •No Fault messages on dashboard display (as left last weekend) •Connected jump lead to chassis earth and fed into passenger foot-well for ease of testing. •PIN 16 (Battery Power) to jump lead – measures 12.45V •Voltage between Pin 16 & PIN 4 (Chassis Ground) – measures 12.45V •Voltage between Pin 16 & PIN 5 (Signal Ground) – measures 12.45V •Continuity of PIN 4 to jump lead – tested OK (beeps) •Continuity of PIN 5 to jump lead – tested OK (beeps) •PIN 6 (CAN High) – measures 2.65V (should be 2.5V to 3.5V), as per TG's C4GP •PIN 14 (CAN Low) – measures 2.33V (should be 1.5V to 2.5V), as per TG's C4GP Key out and Battery Negative disconnected: •Resistance between PIN 6 and PIN 14 measures 61.7 Ohms. Good Ballpark All above sounds healthy. Reconnected Battery. Started Car and let it idle in neutral for 15 minutes. •Topped up brake master cylinder and left brick on foot-brake to help bleed air. •No faults on Dashboard display •Battery measured 14.5V during Alternator Charging I think the car is now ready for us to retest the OBD2 comms with Diagbox & cheap reader for any fault codes and to bleed the brakes and see how she goes. No rush, as time and projects permit. Cheers |
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TriumphGuy
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Member No: #47272
Joined: Jan 13 2017Location: Halifax, West Yorkshire |
Andrew, those readings look good. Some people recommend disconnecting the battery to do the resistance test and others recommend waiting for the CAN network to power down once the ignition has been turned off. I'm confident that it will now be possible to communicate with the C4P and read any fault codes. All being well, once the codes are cleared and the brakes bled, it should be good to go once again. | ||||
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kbg2020
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Member No: #55516
Joined: Jan 30 2020Location: Manchester |
Thanks. Fingers crossed. One thing that I have just noted on the OBD-2 pinout notes. PIN 12 is labelled 'K-Line - ABS diagnostic'. I didn't check this one. Any research on this pin and what it should measure I wonder? I think the second Youtube video you posted mentioned K-Line at some point. Any ideas / tips, as its new to me? Cheers PS. I'm back in Manc now, so will have to be pending. |
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kbg2020
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Member No: #55516
Joined: Jan 30 2020Location: Manchester |
Some further musings / observations on my part. TG, referring back to the link to the Citroen specific OBD2 pinout in your post of Thurs 13th Feb, the PIN 14 (CAN Low) has a description “J-2284 / K-Line Central door locking system”. I only just realised the potential relevance of this – or it could be just coincidental. As follows: My mum says that in Nov/Dec 2019 she had problems (difficulty) locking the C4P door. After struggling for several days (and having to park it outside her house unlocked) she took it to her local garage where they ‘fixed the problem’ (for £100) and it has locked OK since then. However, it was shortly after this, in the new year (early Jan 2020) that she started having the ABS braking fault message come up that quickly led to the incident in my OP that resulted in the RAC recovering the car back to the same local garage. It seems perhaps more than a coincidence to me that the CAN Low PIN has the description as stated in the pinout. What is the relevance of this description? That is, does PIN 14 have something to do with the Central Locking on the C4P as well as healthy comms? If so how / what? I am wondering if something was disturbed on the engine compartment fuse-board / wiring looms in Dec 2019 when the garage ‘fixed the CL problem’, and the disturbance was perhaps rectified (put right again) when I cleaned and re-seated the fuses and D-plug connectors last weekend. I am talking about the black (PM & PP1), brown (PF). Grey (PP2), and yellow (PB) loom plug connectors on the engine compartment fuse-box which I cleaned and reseated. I don't know what all these (acronyms) mean - just reporting what they appear to be on another online diagram / photo of the Fusebox. Hmmmm… any thoughts anyone? |
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TriumphGuy
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Member No: #47272
Joined: Jan 13 2017Location: Halifax, West Yorkshire |
Just seen your PM Andrew. I don't know much about the central locking. I think it is part of the BSI module's function. I suspect that we might find some error codes relating to the central locking once we get Digbox connected. Is the remote working at the moment? There is a way of resynching the remote but I can't remember it off the top of my head. It should be possible to lock it the "old fashioned" way with the key in the barrel. |
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kbg2020
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Member No: #55516
Joined: Jan 30 2020Location: Manchester |
Yeah - I am jumping ahead. Let's wait to see what error codes we get with Diagbox connected. I just thought the recent CL fault history was interesting sidenote. For clarity, the 'remote' button function is not working and hasn't worked for several years. The CL using the key in the driver or the passenger door is working, it was OK until it went faulty in Nov 2019 and was fixed by the garage in Dec 2019 (for £100), then the ECU/ABS/CAN issue reared its head in Jan 2020. I must admit both keys are in a sorry state of being taped-up to stop them falling apart  . I will park these thoughts until we get to connect Diagbox.
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TriumphGuy
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Member No: #47272
Joined: Jan 13 2017Location: Halifax, West Yorkshire |
These are the key fob cases I bought on Amazon: - Click Here - Sorry for taking things slightly off topic. |
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TobiasBB
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 Member No: #55742
Joined: Mar 05 2020Location: Denmark |
"Does anybody know why there's no communication with any of the ECUs through the OBD2 port? The car is a 2009 Picasso VTR+ with the 1.6HDi engine and the EGS transmission. " I had something stupid happen with a peugeot a couple of years ago... one of the pins got pushed 1mm back, so the reader couldnt connect properly..... pushed it back into place and full connectivity was restored (each pin could still be read with a multimeter no problem..) |
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