Hi, folks, just wondering if there are any 360 CAN Bus gurus out there. There is a CAN Bus between the Left and Right Motronic ECUs. Half way between them is an inline connector labelled "18G/14G". Various 360 WSM wiring diagrams (unusually) show a single 120 ohm termination resistor on the LH ECU side of the connector and none on the right side of the connector. However, when wiring checks are done from the plug halves to their corresponding ECUs, 120 ohms is measured on both halves. This has been confirmed on two cars. Checks have only been done with the ECUs plugged in. We are not sure where the termination resistors are. Are they: 1) in the wiring somewhere close to the ECU connectors? 2) inside the ECU connectors (I've seen this on the 355F1)? 3) inside the ECUs themselves, between pins 45 and 61 on the inboard connector (LH ECU) and the outboard connector (RH ECU) on the Modena? On the Spider, this corresponds to the lower and upper plugs on the LH and RH ECUs respectively. Perhaps if someone has a spare ECU, they could measure across these pins? Image shown of wire side of harness connector, so should correspond to the pins on the ECU: Image Unavailable, Please Login Thanks!
Hi Ian. In fact there is only one CAN bus on the 360, hence only 2 termination resistors "close" to the physical extremities of the wires. The CAN bus between the 2 ECUs is the same as the one going to TCU, dash, ABS. I made some measurements on one ECU : pin 29 and 45 are connected together internally (CAN bus H), pin 12 and 61 are also connected together internally (CAN bus L).
I'm always hesitant to respond to more technical posts like this, but I do take pride in knowing that in terms of "normal" vehicles, I'm pretty darn good at CANBUS diagnostics. With that note, hopefully I'm not speaking out my who-ha. So speaking in terms of normal cars, there are typically two resistors through the entire CANBUS circuit: one in the single ECU and another in either the BCM or more commonly the instrument cluster. When I'm chasing CANBUS issues I unplug the battery and check resistance at pins 6 and 14 of the DLC, and if it shows roughly 60 ohm, then wiring for the whole circuit is considered intact (two, 120 ohm resistors in series halves the value) Granted I do not have the knowledge of Ferrari you do, I'm wondering if when you measure the left side ECU you're getting the obvious labeled resistor, but when measuring the right you're getting the other resistor somewhere else in the circuit. Despite the splice being undone, is there another pair of CANBUS out of the ECU? I'm wondering if you're separating ONLY the communication between the two ECU's. You mentioned that the 14G/18G splice is able to be undone - you could technically check the wiring from the splice to the undone connector at the RH ECU, and you could also go directly to the RH ECU pins themselves to see if there is an unlabeled one in there. With the notes from Eric and the way he made some measurements, resistors are placed between the high side and low side, so by mentioning there are two pins for CAN High and two pins for CAN Low, it would suggest that there are two twisted pairs instead of just one? Just my two cents and some thoughts for you. - Shane
Well, visibly, it looks like there are two CAN Busses and two twisted pairs, but basically, there is only one twisted pair which goes from the LH ECU to the RH ECU and through the RH ECU and on to other ECUs. There can't be a resistor in the RH ECU as that would be a third 120 ohm resistor. The other resistor is at the front of the car (at the ABS ECU end). I think Ferrari have put at least one resistor in the Left hand Motronic ECU connector (26L) not in the ECU itself. This is based on my experience with the 355F1. Note that the ECUs are hard to get to on the Modena, so we are doing resistance checks from the inline plug between the two ECUs (14G/18G), not actually checking at the ECU plugs. Image Unavailable, Please Login Indeed, we are disconnecting the 14G/18G plug and measuring in both directions and getting 120 ohms in each case. Also, when we backprobe 14G/18G with the plug connected, we get 60 ohms.
Ian,, What type of issues / symptoms / error codes are you trying to resolve ? I am curious to know for future reference Thanks Dominick
No problem, thanks for filling me in. I'm here to learn as much as I can but try and contribute as well. Unfortunately my experience falls completely outside of the exotic world but some of it translates over. Good luck with the potential issue you're chasing
Unfortunately, now we know the CAN Bus between the two Motronic ECUs is part of a larger network, that means we have to check the car from frunk to engine bay. Our checks show both termination resistors in the circuit, so we are not sure what might be causing the ringing (and possible signal corruption).
I recently helped a friend in Italy with a similar issue, only it was on a 430. In his particular case the ABS module was outputting nonsense onto the bus, which we identified with a scope. Hope you can find it quickly.
Reading posts like this, I wish I could have somebody just completely go through my car electrical wise. I doubt everything is perfect, and it would be so cool to be able to find and fix anything that is not, as far as electrical systems go.
"Seek and you shall find...." There are lots of pros and cons to this. Usually when you go looking for things, you find more than you bargained for (or budgeted for). You know the saying... "If it ain't broke, don't fix it". Of course, the more you work on your car, the less afraid of it you are. Makes you want to tackle some of the more difficult stuff yourself and save some bucks. Unfortunately, recently, I was checking something under my dash to help someone else with their issues and I didn't notice that the pen I was using to take notes was rubbing on the white leather. I tried everything to remove the ink, but then I realised I was removing more leather than ink
Lol it's not a big deal. As you have already read, I'm confident in my abilities with everyday cars. The only reason I'm hesitant on these particular posts is due to people who have as much time experience on JUST these cars, that I do on everything else. I never want to look like an idiot lol. CANBUS is just a twisted pairs of wires that allow communication between all the modules, really quickly. The minute details is where it can be lost on people with data packets, the first millisecond of message over the wires is just a straight up identifier of what module is attempting to send a message, there's priorities assigned to modules, etc. It's kind of fun but also a real bear when trying to figure out communication codes - or in Qavion's case, no code but a message is somehow corrupting subsequent information.
There's a good chance that that Lecroy O'scope supports CAN bus decoding. If so and properly set up, it'll tell you everything that you need to know as to the activity on the bus. https://cdn.teledynelecroy.com/files/pdf/canbus-datasheet.pdf
Thanks for the note. Could not find any mention of CAN capabilities in the manual; it's a very low-end scope. Any thoughts on the quality of the signal?
At first glance on Yelcab's scope picture, there's definitely a glitch on that bit. Probably a bad CAN BUS transceiver chip in one of the master/slave devices that's attached to the bus. On your scope picture, that glitch is not as pronounced and it looks like it occurred at the end of the data frame; depending on how that O'scope oneshot was set up, triggered and captured. The termination resistors losing tolerance is another possibility. Usually it's 1% or 5% tolerance for automotive. CANBUS uses a voltage differential protocol. Make sure that the ground points on the chassis are good, especially the grounding trees. The best chance of getting this problem resolved is to get a scope that supports CANBUS with symbolic trigger and decode.
Appreciate the feedback, and have two questions. 1) I've got a problem on one bank of my 360; I'm wondering if the bad bank ECU is getting a corrupted parameter from the CAN bus pictured in this thread. I can provide the details if you like; it's a little involved. My thought is to get a CAN analyzer and graph the value of the suspect parameter versus time. If the parameter reveals suspicious behavior, I'd move forward with diagnosing the bus. Your thoughts? BTW: I performed a resistance check that suggests 117 ohms when the expected value was 120. Not certain if the 117 number (representing a 2.5% deviation) is due to a bad resistor or a bad measurement. 2) Are you aware of any 360 schematics or illustrations that reveal the physical locations of the termination resistors and/or the master/slave devices?
What's the story about the bad ECU? What are the symptoms? Sure, I'll take a look at the details. Accessing the CAN data is not a problem, but making sense of the data will be a hurdle. You'll see tons of node IDs and messages, but what IDs of the nodes and messages correspond to which module on the car? That's something that only Ferrari developers of the firmware have. As to the resistance check, taking a measurement on the CAN H/L line will include the resistance of the wiring. You'll have to isolate the two resistors from the wiring to get the actual value. But since the maximum bus length and node distance is 40 meters according to CAN BUS spec (which is not the case in a car), 117 ohms is fine. See this post regarding the location of the termination resistors. https://www.ferrarichat.com/forum/threads/360-f1-wont-shift-passed-2nd.570401/page-3#post-146001535
I'll put a summary together. I'm only interested in one CAN ID, which I have. An FChat guy (JazP) did some reverse engineering work to establish some IDs for 430s and 360s. The CAN software ("CANdo") tech rep says I can filter out all other IDs and output my ID of interest in Excel format. Much appreciated.
The 360 wiring "hookup" diagrams don't show the location of the resistors, they just indicate that resistors are between one plug and another. On my F355, the CAN Bus resistor was actually inside the ECU connector backshell. I suspect the 360 is the same and one of the resistors is in the LH Motronic ECU backshell ("26L"). Since the ABS ECU is at the furthest point from this, I suspect the other resistor may be close to the ABS ECU in the frunk. i.e. not in the backshell but close to a small connector "22B/2B" near the ABS ECU. This resistor is called "R120ΩB", also suggesting it is in the frunk area, not near the instrument panel (as suggested in the other thread). Image Unavailable, Please Login https://www.scribd.com/document/338159768/Ferrari-360-Spider-Wiring-Diagrams FWIW, my F355 resistor had a tolerance colour band of 5%
Summary attached; let me know if you see logic errors or something lacking clarify. I tried to keep the word count low.
Apologies, but one minor correction seems warranted given the really good info on this thread… The resistors are in parallel, which correctly measures at half (when the two resistors are the same value). A series connection be additive.
