Volvo EC250 EL Theory of Operation question

Greetings all!

Had an issue pop up today on an excavator. The machine is

Volvo
Model EC250EL
Serial VCEC250EK00310165


Symptom as described to me: This box ↑↑↑↑↑ (main power relay I expect) Seems to fail to latch when the small control toggle switch is turn on. Naturally, the machine will not start while it is bouncing, but after sometimes 6 tries, sometimes more, it will latch and everything works. The machine starts and everything in the electrical system seems to operate as it should. However, arbitrarily, this relay, if that's what it is, will break during operation and the machine will die and the operator has to climb down and work the control toggle a few times to get it to stay latched. Customer's service guys have replaced two relays in the fuse panel to the left of the view from taking the picture.

Before I rip into it, I'd like to know a)what it is and b)how is it controlled, by the small toggle switch by the door and through the relays, or directly, or just how. The owner wants to just pull it and open it up, but he doesn't understand what controls what or how.

Is the wiring entering the enclosure the trigger wire or an output signal carrier? I really need a piece of a schematic. But if someone can explain exactly what is supposed to happen when the control toggle is switched on it would help. I just don't care for diving into something I don't understand pretty well. Ops Dir wants to just replace it. I'd rather not bury it in dollars, but since I don't know the system....

Suggestions?

Here you go Tony.

UNO MAS

Muchas gracias, jefe!

Seems to first point to SW3101 on page TW-2. Something funny about that switch. The LED flickers as the EBDS bounces, and even with it not lit, there is or can be power through the disconnect. At times it doesn't seem to matter even if the switch is in off position, there can be power through the EBDS. Incoming voltage is 24 on one of the supply wires, but a little low on another, I assume should be 24 also. It's only 20.4 or so. I can't see why or think of a reason that it should be, and I didn't track that wire back to the next connector to see if there was trouble there. That's next, once I figure out where it goes. If that should be 24, and that is the control voltage for the EBDS, I can see why it's bouncing. But why at some point it does latch I can't explain. I used Deoxit on the connector, which was already pretty clean in appearance, and tight, but it's a good habit.

I drove the thing around and twirled and danced it for half an hour once the switch made...and stayed. I left (and left the switch made) and told the operator to run it. He said he got 5 feet with it and it quit. Hmm....

I'll be back

It's getting thicker and deeper. Now I find out all of this has been going on since the big ice/snow storm we had back in Feb...

And even though I can get on the machine and run it, in just a few minutes, the regular op gets on there and we get a code, and threats to derate.

U008088 Vehicle Communication Engine Subnet - Bus Off
Failure Event:
Electrical Error on Engine Subnet (J1939)
has been detected.

Symptom:
1. Low power because of engine protection
2. SCR system does not work properly
3. Display messages about ECU Communication problems
4. Will activate engine will derate and trigger DTC P20EE84
when derate level 1 is reached , and DTC P20EE16 when deratelevel 2 is reached.

Conditions:
None

Possible causes:
1. CAN communication failure.
2. Damaged wire harness or connector.
3. Internal error in the Aftertreatment
Control module (ACM).


That's from our laptop. Below are screenshots by the operator during run time.




Now I have no clue as to whether this is related to the intermitent EBDS or not. And today, even with the toggle switch off, LED off as it should be, the EBDS and the key off, it tried to make on its own, clicking about 5 times. None of this makes sense to me.

I'm at your mercy

If memory serves, the a/c controller and the caretrack controller are both on the hot side of the battery disconnect. I think one or the other controls the disconnect through the HMIM controller. I do remember before closing down, we had one that had a defective ACM causing havoc on the backbone. This is some next level electronics. Super high speed data, way faster than anything before. I would reach out to the dealer in this case.

I'm not sitting with my laptop right now, so I don't remember what the relay numbers are. But I am curious if the relays that have been replaced were with oem relays. Just today I was working on a loader with a similar issue. Customer removed a relay and found bad corrosion and replaced the relay with one that looked similar from the local auto parts store. The relay would work but after some time it would begin to fail and cause all sorts of problems. The oem relay is rated for higher amps and has a diode inside which the aftermarket one didn't. I put in the correct relay and the problem was solved. I would make sure that the correct relays has been installed and not just any relay that would fit. If it has the correct relays then as FWF said it would need for the dealer to come out. Volvo has some of the most over the top and remarkably complicated systems. I'm not saying that you couldn't figure it out on your own. But Volvo is not conventional when it comes this sort of thing and is very different from anything else that I have worked on. Like I said before over the top and overly complicated when it isn't necessary. I don't know any of the guys working at the dealership in your area so I don't know how good any one of them are at troubleshooting electrical. If you do decide to call us out to look at it you can request for me to look at it. That may or may not work, but I get customers a lot that will only deal with me and no other.

Tony Wells said:

And even though I can get on the machine and run it, in just a few minutes, the regular op gets on there and we get a code, and threats to derate.

Click to expand...

Maybe your operator is the problem.
Some operators can tear up a steel ball in a rubber room.

Thanks for chiming in, FWF!

I think it's sort of unorthodox to approach post shutdown actions such as the "Aftertreatment" the way they have. I mean, it does make a sort of sense to do those things, but it sure seems they went the long way around to make it happen. And I don't understand their reasoning for handling the battery disconnect with so many subsystems involved. I guess I'm complaining about over-engineering. The tighter the systems are integrated, the more likely (or simply possible) one small issue runs rampant through several related systems. Then those system display problems that aren't really problems with that system itself, but a connected system. And unfortunately, there is not always a positive way to separate these interwoven systems to narrow down where the real problem is.

That's where the Dealer training has to take over. And these days, it seems that the industrial machines are getting like autos and trucks. Tech is evolving faster than it can be absorbed in the field, and then replaced with new tech far faster that it used to be.

Do you think this EBDS flaky operation is related (or could be) to the communication failures? As I mentioned, this all started with the ice storms we had. I can't draw a firm conclusion, but if the machine was covered with snow and ice and left to thaw out on its own, then I can see a chance for water or at least some moisture ingress in virtually any connector exposed to that.

I hate failing, but "A man's got to know his limitations". I'm fairly conversant in electronics, and have worked in systems integration in a hospital environment with life safety data, no I'm not totally ignorant of what has to happen, but this is special to Volvo, and there's a reason Volvo techs get trained, get dedicated instruments, and lots of tech data. On this one, I may have to bail out.

Oddly (not a happy coincidence) we use this to feed our primary grinder, a Diamond Z. Well, it went down today. So we're crippled a bit. Yes, we have probably at least a dozen hoes (including the 460 I have to replace the burned wiring harness on), but most are too small to keep up with the Diamond Z. Plus they have no working A/C....and before you call the ops lame, it's not the temp alone. The could run with the windows open, but that's not healthy in the environment created by grinding rotted compost material. So the enclosures are necessary.OK, I've whined enough for one post.

Thanks for "listening"

By the way...
Yellow warning means a problem occurred and is still a problem. Blue warning means that a problem happened, but currently isn't a problem at the moment. But you need to check it out.

Paul, that code posted comes and goes on its on. We can hook up to the diag conn and start the machine, and maybe it will be there, and maybe not. That I thought would have been a hard code. We aren't clearing any codes with our laptop. That one is just hot or miss.

And yes, you may be right. I spent enough time on it to dig a 10 x 10 x 40 trench, fill it back in...picked up and tossed arounf(it has a claw) probably 15,000 lbs of logs and stumps (which is the majority of what it is used for) and never got a code, never missed a beat, died, or anything it wasn't supposed to. I could have been feeding the grinder....I saw nothing different about what the op does that I did. He's a seasoned lumber man, and a good operator. It's puzzling. I even pounded the ground packing the fill for the ditch I dug. Got pretty rough with it....nada.

I'll double check on those relays though. I don't know where they were sourced. I sort of doubt they came from Longview. That's about an hour and a half round trip and our service manager probably didn't want to make the drive. But I'll see what happened there. There's more to relays than meets the eye. And not all cross references are 100%.

Being that this is such a sophisticated system, I just had a thought. How sensitive is it to low level RFI? The grinder can be remote controlled, and the op usually sits in the hoe cab with the radio to run it while feeding it. Seems that if that was a risk, they would have provided adequate shielding, but thought I'd mention it.

Yes, everything has shielding. That said, i have had an older 2-way kenwood cause RFI on a J1939 network. Caused all kinds of grief with emissions. That was on an L150G loader. The hoes are just as bad. The engine might operste on J1939 but the main comms between components is on TAE or something. Its like double CAN speed. You have multiple backbones, with dedicated comms.
Is there any chance, this machine was jump started? You said the problem started during ice storms. Volvo, as you know is very fond of diode suppression. If somebody improperly hooked up cables or used a welder, you could have multiple issues .

I can say with near 100% certainty that if it were jumped, it would not be with a welder. We've had some mishaps and pretty much no welders on site unless they are on a specific job, and right now there are only a couple of us authorized. The other guy knows better as do I. Yes, I've noticed the plethora of diodes on Volvos, for sure. If it were jump started at all, which I sort of doubt (the batteries are pretty fresh and plenty hot) it would have been with a jump box, nothing else.

I just mentioned the radio because I didn't use it during my testing since I was not running the grinder too, but thinking about it, we got a load of baled cardboard in while the op was on it just driving it around and not grinding,..and got the codes. RF is funny stuff though. The remote for the grinder is powered through an accessory receptacle AKA cig lighter.

Does it have an "operator presence" switch in the seat?? Or, is there a wiring harness that the seat is rubbing against somehow? Just trying to verify a reason it codes for the normal operator, and not for you.

No, it doesn't...that I know of. I don't ever just reach over and crank a machine anyway, out of habit and have not tried it with this one. I have about 30 lbs on him, but he has been running this machine for a while now with no issues.

Have you checked batteries yet?
Cable connections ?
If you are finding 20 volts in the main power system there might be bad connections.
Bob

Yes indeed, Bob. See post #14.

I have not traced it out, but it occurred to me later that the 20.4 VDC I was reading may be the LED supply, unloaded. It's common in the electronics world to use a dropping resistor to drive an LED from higher than ideal DC supply. When not loaded with the LED, it could be just reading it with the 20,000 ohms-per-volt impedance of the meter I was using. Can't get to it when it is actually driving the LED, assuming I am correct on that. The rest of the system is all at least 24.3 at rest, and only drops to maybe 11.9 while cranking. Cranking speed is normal, and the EBDS still does it's clicking with a 1500 amp jump box hooked up. Really not thinking it's a battery problem.

Where are you reading the 12 volts cranking?
Bob

Several places. Final battery in the series to the neg terminal, and to the chassis gnd. Either side of the EDBS. Can't reach the starter, so not there (but there is no cranking issue). And the main power stud in the fuse/relay box left of the batteries.

The engine starts easily and I only have a few seconds to make the measurements.