DDEC comes on unreliably

[Sebulba]

If I read your thread correctly. you have a 60 serries ddec late 1997ish. Prob ddec III. pre egr(that's great!)  The working of ddec is not as complicated as it sounds. Your engine will not start without it!! It controls injectors Fuel supply. Also timming of them. Couple of must. Will not do this without power seperate from main elect system. requires direct battery connection for power+ and neg-.Main reason for this is memory. A seperate power supply from ign switch Wire code 439 + is required to wake unit (that is bus system source for power) =main disconnect on. Been there on this one as I have built total electrical system from burned out system on my 98 prevost. The other front end info system is exactly that. Clean connector of check grounds on coach side. Clifford has been there on this and some of novices have also. You might have DDEC IV there was a change in late 90's My 2000 -60 serries is IV.   Bob

Hello Robert,

Going to have to digest your post, but I'm learning. 

How can I tell if it is III or IV? Might be good to know in future.

Also since DDEC is always hot direct to battery, what about when a guy changes batteries, this obviously disconnecting DDEC from power?  Lost memory or can it handle short disconnect?

Thanks a million.

Seb

[Sebulba]

The SEL (red one) stands for stop engine light which will shut the engine down. It is a major fault. The CEL (yellow one) is for minor faults. It warns you of an issue but won't shut you down. You should have a momentary switch located near the lights which will put the lights into a test mode and if all good will flash 25 on each one.

Hello Bill,

So, when I hit main power I am supposed to see lights like these?  I will check tomorrow.

I have never noticed anything like this, but haven't looked for them.

The wait till they go out to start engine?

I just read the engine start procedure in my manual and it just says to turn on main power and hit start.

Not sure what I'm missing.

Thanks

Seb

[Sebulba]

The SEL (red one) stands for stop engine light which will shut the engine down. It is a major fault. The CEL (yellow one) is for minor faults. It warns you of an issue but won't shut you down. You should have a momentary switch located near the lights which will put the lights into a test mode and if all good will flash 25 on each one.

Hello Bill,

I just turned on main power and saw nothing like SEL or CEL light up.

The momentary switch you mentioned, do you mean the one that lights up all of the dash lights?  I pressed it and saw nothing that looked like SEL or CEL. 

Flash 25?  Sorry don't know what youean by that.

Boy, I've kinda been a motorhead all.my life, but these are a whole knew animal

Thanks for you patience and assistance.

Seb

[Sebulba]

The information panel has a plug end harness it just needs cleaning no fast idle the cruise will not work either ,the turn signals should work they just don't show, the joys of electronics will keep you busy

Hello Luvrbus,

Maybe the connector to that little box on the dash or elsewhere.

I did take the box off and this disconnect it and put it back.  The connector looked ok, but I didn't actually clean it.

FYI these symptoms are not different before or after that removal and replacement of the DDEC dash box.

Thanks

Seb

[Sebulba]

You always need to remember the Detroit responsibility stops at the ECM anything past the ECM is the OEM responsibility and that varies a lot from 1 manufacture to another, 99% of the troubles are on the OEM side

Hmmm,

Seb

[luvrbus]

You DDEC has a backup  battery inside the ECM

[Sebulba]

You DDEC has a backup  battery inside the ECM

Ok, good to know

Thanks

[buswarrior]

The many variables...

Stock, the computers bypass the main disconnect, to keep the computers "alive" for regular operations.

For a busnut, that's a battery drain when the coach gets parked or stored for extended periods.

If changed to be switched, those computers may need time to come back to life, after being disconnected via a battery cut-out switch?

Add in the internal battery, as luvrbus notes, if it is unhealthy... never met any kind of computer that operated correctly, once the internal battery stopped functioning correctly...

The lack of start-up system check SEL and CEL, does it correspond with the other loss of function of the Driver Display, et al?

Happy coaching!
Buswarrior

[luvrbus]

The SEL and CEL are not activated by the main disconnect those are activated by the ignition switch on the dash ,turn  on the disconnect then the ignition switch the lights should come on for a few seconds then go off ,it is not going to start if SEL and the CEL are not working

[robertglines1]

to retrieve codes you could need to turn switch to power. Stop don't start. then off and on to power again(don't start.. codes should appear.  Most common problems with communication harness is corrosion at Deutch 31 pin connector.//connects engine harness to coach wiring harness. 2nd most is grounds corrosion. 3rd dang mice chewing wires..

[luvrbus]

Check the bulb sockets for corrasion on the SEL and CEL   

[RichardEntrekin]

Here is another way of checking out what is going on.

On the right side of your DDEC you will find two plugs. The upper will disengage if you use a hooked tool or small screwdriver to release the latch.

The lower is held in place with a bolt that has a 1/4 head. A nutdriver is the tool for removing.

Take them both loose from the computer. On the upper, which is main power supply, the red and black wires are about 12g. You should have 12Vpos on the reds when comparing to the grounds on the plug (blacks).

On the bottom plug, second row from the bottom, position B3 (pink wire) you should have 12V Pos when the ignition is on.

This quick test is going to tell you if the DDEC is getting the power it requires. If it is, then your problems are all up front with the lights or circuits that power the indicator lights.

Be very careful in replacing the lower 30 pin connector to ensure you don't bend any of the pins on the computer.

[Sebulba]

The SEL and CEL are not activated by the main disconnect those are activated by the ignition switch on the dash ,turn  on the disconnect then the ignition switch the lights should come on for a few seconds then go off ,it is not going to start if SEL and the CEL are not working

Ok, I still don't find SEL or CEL.

Are they in the right and left idiot light panels?

If so, I looked in my operators manual and see nothing saying that.

Thanks.

I really appreciate your help.

Seb

[usbusin]

Seb, does this website help you at all?  I can hear the frustration you are having.

https://busdoc.i.daimler.com/public/fct/_neutral/obd/usa_DDEC_IV.pdf

[usbusin]

From what I see in your posted pictures, the SEL is Stop Engine and the CEL is Check Engine.

Looks like both the CEL and the SEL are lighted.