Well with the changing seasons, the random headlight issue and excessive parasitic current draw has come back. There was some hope that an unrelated update for the BCM would take care of the issue. That, pretty much as expected was found to be untrue. Luckily during the summer, I included two ways to charge my starting battery, a shore power charger
and solar charger option.
So at least I can keep the battery from being destroyed. (Wrong)
So back to the hunt. I pretty much realized that taking this back to Ford to track down would be fruitless, so I decided to dig in. In a previous life I worked on some complex issues, and the first rule of debug was to try and make the problem repeatable. Luckily for me with return of wet colder weather that has pretty much turned to every night.
One thing I looked at was the fact that rain returned. I know most people think it rains all the time here in Oregon. If you spent any time on the Transit Forum you heard of the water in the air filter issues. So, I did spend some time looking into this, mainly because the return of cold hit before the rain. I didn’t relay see the issue until I had both. That issue was I believed fixed in 2019, but it does get wet inside the engine compartment. I did clean out the weep hole and added additional hole for the windshield cowl draining system. I added a cover for a suspected connector, to keep it from getting wet. That appeared to be a red herring, as the problem was still prevalent.
I also completely disconnected the power steps, as they must sniff the CANBUS to determine if the door is open or closed. The power steps were added after first seeing this issue, so I was confident they had no issue with the problem. If I do have to back to Ford, I want to rule out any 2nd party culprits and keep the focus on the real problem. So, this may give you some insight to as where I am going the CANBUS. Unfortunately, or fortunately modern vehicles are dependent on CANBUS communication.
As you can see, there are five major Buses in this vehicle, a couple of high-speed busses and other medium speed buses. This doesn’t even include some of the private busses between modules. The gateway module is where all these buses come together, as it can also transfer information from one bus to the other. The gateway also has the DLC connection (OBDII) port connection.
The bus that I focused my concern at was HS1 CAN. It has the modules that are most likely involved in this issue, mainly the BCM, but it would be possible for an issue to transfer from one bus to the other. My first thought was to put a can bus sniffer on, to see if I could find out who was sending the BCM a bad message to turn the light on. That would be prudent, but you would have to catch the failure and have the documentation to understand the messages being passed. While I have a basic understanding of the protocol, it is not easy to get the information needed from Ford. Reverse engineering could take a sometime.
I was also using the data I had from capturing current data last year. That data led me to believe the problem was a possible bus problem as it would happen when there was known bus activity or at least I perceived there was activity based on the time cycle seen. The fact that temperature & humidity had a large effect on the issue. I spent many years running equipment in temperature chambers, so no convincing needed.
My next thought was through a scope on the bus to see if anything looked out of the ordinary.
Unfortunately, I don’t own a scope, and while I’m always looking for a reason to get one, I’m not sure this rises to threshold to purchase one. At least not yet.
I still have a few things I can do with a basic DVM, one would be to measure the voltages of the HS1 CAN +, and HS1 CAN – lines, that would be relatively easy, but determining that data depends a lot on the knowledge what is going on bus. So that leaves us with basic measurement on the termination of the bus.
CAN stands for Controller Area Network and it runs on a 2-wire high speed bus. To prevent reflections on the bus, it needs to be terminated on each end of the bus. Going back to one the previous diagrams you can see where the termination for the HS1 Can bus reside, the PCM module and the Gateway module.
When you go to measure these, you are going to need “needle probes” to easily get to these connectors, these will allow you to back probe the connectors. I couldn’t find my older needle probes, so I had to order some. While I was waiting, I took the Communication module off, and measured all the bus connection to verify that they have a 120-ohm resistance between the HS1CAN - and HS1CAN +, I check all the can busses going to the module.
I got my needle probes and was able to measure the connector going to the Gateway Communication module. The bus that I am looking at are pin 19 & 20, when I measured this, I got 60-ohm.
This was surprising in that I was expecting 120-ohm. 60-ohm would be what it should measure if the Gateway module was connected. Two 120-ohm resisters in parallel would equal 60-ohms, this leads one to believe there is an extra termination on the bus. Of course, to be sure, I connect the gateway module and measure between high & low and get 42-ohms.
I must say that I was kinds of surprised, as it seemed to simple. When checking the bus, you are really looking for something between 55 & 65 ohms. 42-ohm seems pretty far out, and for the most part this major bus has not shown any errors.
From the diagram above you can see that this bus goes all over the van. It seems like a simple divide and conquer attempt should be the best way to move forward. Seeing that the PCM is supposed to have the other bus termination I decide to go to a connector that I already know is easy to access C139. This is the same connector I thought might have moisture issues
Now when I remove this, I am really expecting to see 60-ohms on the bus, thinking that issue is on the other side of the connector. Instead, the issue travelled with the PCM side.
Bus with C139 Removed
I then moved to remove the AWD Module, no change in issue. So that kind of leaves me with the PCM. I thought about re-flashing the PCM, but with a bus termination so far out, I was afraid of the quality of the update. I decided to make an appointment with the dealer to see what they have to say.
My appointment didn’t go well, it was pretty much a replay of the first time I took it in. Yes, we believe there is a larger parasitic draw. You have stuff hooked up to it (Chargers). One out of your dual batteries is bad. The BCM might turn the lights on if the battery is low. I never received an answer about the Can-Bus termination. I will regroup, I made an appointment to another Ford dealer as I need to collect data for Lemon Law data.
Thanks for letting me vent.