DDEC frustration

[Iceni John]

During my desert trip a month ago the CEL and SEL both came on;  I immediately pulled over, checked the coolant level and temp and oil pressure and found them all OK.   The engine did not shut down, so I cautiously continued the last few miles.   Two days later the engine started OK, but the CEL and SEL came on several times on the drive back home, again without the engine shutting down.   I read six codes from the CEL's flashes:
12  -  Power Take-Off Speed Adjust high voltage,
36  -  Oil Pressure Sensor low voltage,
41  -  Timing Reference Sensor pulses fault
44  -  Oil or Coolant Over-Temperature
45  -  Low Oil Pressure
46  -  Low Battery Voltage

Last Saturday I started up the bus to top up the tank (diesel's dropped to $3.79 here!), but after about two minutes idling while building air the engine shut itself down with the CEL and SEL both on.   When I tried to restart, neither the CEL or SEL would illuminate at all for the few seconds before they normally go off, and the engine would spin but not fire.   Again I checked the vital signs  -  both batteries were about 12.8 volts, there was good oil pressure, and plenty of coolant in the expansion tank, in other words no obvious reason for a shutdown.

A few nights later I tried to start again;  for the first few tries the CEL and SEL did not come on at all and the engine turned but did not fire, but then they finally came on as they should and the engine fired right up.   However, after a minute the engine shut itself down again with both lights on.   This evening the engine fired right up, but both lights came on after a few seconds so I shut it down.   The same six codes are still flashing out on the CEL.

I've been reading through my DDEC II Troubleshooting Guide to try to understand what's happening, but the more I read the more confused I get.   I don't think I have a PTO, so Code 12 is a mystery to me.   This evening I measured the voltage at the Oil Pressure Sensor and got 5.06 V there, right in the middle of the desired 4 to 6 V range, so shouldn't that eliminate Code 36 as a reason for the shutdowns?   I have no way to check Code 41  -  maybe that's the culprit?   The oil and coolant temperatures and oil pressure all seem to be OK, so shouldn't that eliminate Codes 44 and 45 as possible reasons?   My starting batteries are both healthy, and the DDEC fuses are getting about 12.7 V, so why Code 46?   Unfortunately I don't have a DDR, so I don't know how many of these six codes are historical and how many are active and triggering the shutdowns now.   (Too bad DDEC II doesn't show active codes on the SEL and historical codes on the CEL, like later DDECs do.)   

One thing I changed when I relocated my starting batteries last year was to have the three DDEC fuses now wired after the main battery disconnect switch, not directly connected to one of the batteries as before.   I did this to avoid the battery the DDEC was connected to from always draining down, and since making this change that battery has always held its voltage without a problem.   Could having the DDEC now connected this way have possibly damaged the ECM?   What exactly is the reason for DDEC to be directly connected to the batteries?   And yes, these three fuses are OK, and the four DDEC cube relays in the bus's main JB also seem OK  -  if these weren't, the engine wouldn't start?

I've also cleaned all the connections and grounds for any sensors I could find, such as low coolant and coolant temp.   I don't think this is a likely cause of my problem, because my bus has absolutely no corrosion and has always been in dry CA  -  I haven't found any poor connections anywhere so far.

So, do any of the resident gurus and cognoscenti here have any ideas to save me further anguish?   If I have ABC Bus look into things, I'll be spending more than I paid for the whole damn bus.   I've said it before, and I'll say it again now  -  I wish I had a nice simple MUI engine.   Fuel, air, compression  -  that's all I need in a diesel.

Thanks,
John, feeling VERY exasperated

[Ed Hackenbruch]

John, i have a nice simple MUI engine so i don't know anything about the  DDEC engines.   Did you try disconnecting the battery cables for a few minutes to see if that will clear/reset it?

[luvrbus]

Isn't 46 low backup battery voltage you probably get that from not having the ECM hooked to the batteries the DDEC1 is the only DDEC you can reset by disconnecting the batteries could be you need a new backup battery now.


I would hook it back direct to the batteries and see also I have been told the 3 main grounds on the ECM need to be on a common ground terminal

good luck

[Iceni John]

My book says that 46 is "Engine running with low battery voltage (less than 10 volts) for more than 30 seconds".   I assumed that meant the starting batteries which are healthy, but maybe I'm wrong.   Does DDEC II have an internal battery in the ECM to save the codes, or are they saved by some non-volatile memory that doesn't need a constant voltage input?   When I bought the bus it had been sitting for a few months without any batteries at all, and when we connected one Group 31 it fired right up with only a whiff of ether.   This makes me think that the ECM doesn't need a constant voltage to preserve its functionality, but maybe it does?   After reading old postings here about related problems, some folk seem to be running their ECMs after their main battery disconnects, but there must be a good reason for Detroit to specify running the ECM straight off the battery.   Perhaps I've been too hasty in changing it.   Luvrbus, I'll take your advice and rewire the three DDEC fuses to how they originally were off one battery, even if I have to occasionally charge that battery to keep it from going down.   I'll also make sure all the DDEC grounds are to one place  -  I think they are now, but I'll check.   I still hope I haven't damaged the ECM by what I did.

I won't have time until next week to do more diagnosing, but I'll switch the batteries back on tomorrow morning and leave them on.   As far I know I don't have any other phantom loads except for the tachograph (and I can disconnect it, not that I have any cards for it anyway), so maybe keeping the batteries on won't be the problem it was before, especially now that I have a decent charger to top them up.

As usual, Luvrbus has come through with more words of wisdom than I could ever have hoped for.   Thank you  -  you're the best!   I'll post again next week when I've had some more time to get my hands dirty.   I feel slightly less bummed out now.

Thanks, John

[Sam 4106]

Hi John,

I think luvrbus has solved your problem. When I was having the same situation, crank but no start, a good mechanic told me that the ECM has to have power all the time. My problem was that whoever installed the wiring for my engine had installed a solenoid in the circuit that was only powered when the dash switch was on, 8V92TA DDEC II transplant into a MCI8. The solution was to eliminate the solenoid so the ECM was powered all the time. The engine has started every time since the solenoid was removed. Our bus sits in my shop all winter with only an occasional battery charge without going dead. I think by disconnecting the tachograph you will eliminate the problem of the batteries going down. By the way how do you get the codes to flash? I don't have a manual for my engine so I don't know how to flash the codes. Thanks.

Good luck, Sam

[belfert]

My bus has the DDEC set up from the factory to get voltage all the time even with disconnect turned off.  My batteries will go flat in a week or two if I don't keep a battery tender on them all the time.  I have a Vanner equalizer so just one battery isn't taking all the drain from the DDEC.

[buswarrior]

Fix code 46 and watch the rest disappear?

I only know enough to be ignorant.

My money is that all those other codes would be thrown by the same conditions that threw the code 46.

Clean and check grounds.

How old are your batteries? What happens to voltage at the ECM before, during and after a start?

Did someone mention grounds?

I'll mention it again.

GROUNDS.

Start there, ignore the others until you make 46 go away.

happy coaching!
buswarrior
happy coaching!
buswarrior

[robertglines1]

Have batteries load tested indivually.  was a ghost that got me several years ago.  showed good on meter but on fell on face under load.  Prob not your problem but keep in mind.   Bob.

[Iceni John]

By the way how do you get the codes to flash? I don't have a manual for my engine so I don't know how to flash the codes. Thanks.

Crown put a momentary switch next to the DDEC OverRide switch which makes the CEL flash out the codes in numerical order.   Easy!   I wish I had the DDR code reader, then I would be able to erase all the historical codes and see what the active ones are.   For all I know, the present fault could be the same code over and over again, or it could be different codes each time  -  without the DDR I don't know.

I just turned the batteries on, and I'll leave them on until I have time to play with things next week.   I'll definitely be restoring my DDEC to constant power next week, as that's what the collective wisdom here suggests.

I'll report back next week with the results.   Can you believe this problem happened on the same day I finally got my toilet working?   After three years of back-breaking grunt work installing the four tanks, making a water-distribution center, relocating the starting batteries with new slide-mounts, making a generator slide-mount, making a spare tire mount under the front, all this to have a working loo, then that same day the darned bus decides to not start.   Life's not fair!   Anyway, to try and forget these woes, I'm off to Yosemite tomorrow to hike up to Half Dome  -  a non-electronic weekend sounds attractive at this point.

Thanks, John     

[RJ]

Anyway, to try and forget these woes, I'm off to Yosemite tomorrow to hike up to Half Dome. . .

John -

If you are coming/going into/out of Yosemite on Hiway 41, I'm just an hour S of the Park in Fresno.  If you've got some time, give me a call, I'll buy the Pepsi!  Five 5 nine, 2 six zero, four one zero 6 will get thru to my cell.

RJ

[Ed Hackenbruch]

See? i told you i didn't know anything about them!!!!

[jimsflx]

john,my mci with ddec 2 will run down the batterys in a week or so. so i ran a cutoff switch to the ecm ground to cut power to it. if it did not have13.1v from the batterys it would turn but not start after a week or so. a shot of either and it would fire up .goodluck jim

[Iceni John]

john,my mci with ddec 2 will run down the batterys in a week or so. so i ran a cutoff switch to the ecm ground to cut power to it. if it did not have13.1v from the batterys it would turn but not start after a week or so. a shot of either and it would fire up .goodluck jim

Interesting.   I heard that DDEC only draws a few milliamps when it's not actually working, such as when the engine is off, so two big 8D batteries shouldn't be running down so quickly just from the ECM's standby load, should they?   Maybe you had another phantom load, unknown to you, that was quietly sucking your batteries dry.

As I mentioned, my bus is starting fine (at least, when the DDEC isn't playing possum) with less than your 13.1 V at the batteries, but I was still having both lights come on while driving, when the alternator is producing about 13.7 V.   Mind you, even though the lights were briefly coming on while driving, the engine wasn't shutting down (thank goodness).

Ether isn't going to help start the engine, even though it will do so for a few seconds.   The issue is that the ECM is either not coming on at all, or it's shutting down, and without the ECM working the injectors won't inject.

I'll see if keeping constant power on the DDEC changes anything.   I'm worried I may have done some harm to the ECM by depriving it of its electrons.   Luvrbus suggested there may be an internal battery inside the ECM that could have run down  -  definitely plausible, but there's no mention of such an internal power source in any of my DDEC literature and manuals.   Perhaps I need to call the local DD folk and pick their brains about this.

On a sort-of related subject, as I was walking past the local fire station last night one of their ladder trucks set off down the road with its lights and sirens on.   It sounded like a 8V92  -  I think I'll ask them who services it.   Maybe that would be another possible resource to help solve my problem?

Thanks guys, you're the best
John       

[luvrbus]

John, can you get the serial number from the ECM and do you have any idea what version of software you have ,the Pro/Link should  give you that information

good luck

[Iceni John]

How/where do I find the ECM's serial number?   I have no idea what software version it has!   I'll try and look next week when I have some time.

Maybe I need to bite the bullet and buy a reader.   Is the Detroit DDR the same as a Pro Link?   Don't earlier DDECs like mine use a proprietary software protocol that regular readers can't interpret correctly?

At this point I really need to clear out all the historical codes, then I'll have a better idea what's happening now.

Thanks, John