DDEC Issue again...

[Sebulba]

The power and ground usually are 12 gauge wires. Luvrbus would have more knowledge with MCIs then I do. My Bus is a GMC so the DDEC set up probably is a little different.

Sure, I understand about the familiarity with MCI vs GMC etc.  I sure appreciate your help.

So those may be the power wires to the DDEC. 

Would it be any problem unhooking them to clean them?  IE: losing power to the computer for a few minutes or a half an hour while wire brushing and whatever?

Thanks

Seb

[Sebulba]

I took the covers off of these and the connections look good and have electrical grease on them.  Maybe looks can be deceiving though? 

I don't want to open up a can of worms by unhooking them to clean them up.  If there would be no harm in disconnecting them and cleaning them I will happily do it.

Thanks

Seb

[chessie4905]

Do you have the ddec III, IV troubleshooting manual? Did you download a copy? It is available from several sources.
I found them at ddecIV troubleshooting tree. If you already have it, never mind.

[Sebulba]

Do you have the ddec III, IV troubleshooting manual? Did you download a copy? It is available from several sources.
I found them at ddecIV troubleshooting tree. If you already have it, never mind.

Sorry, no I didn't know of this manual.  Sounds like a good resource.  Let me see if I can find it.

I'm not sure which version I have.  I have a 1997 MCI 102 D 3 with a series 60 engine.  Is that DDEC III/IV?

Thanks

Seb

[luvrbus]

The trouble shooting manual is 500 pages thick and are sort of useless till you get the concept on how the DDEC works, the DDEC application manual is more help if you can find one   

[Sebulba]

The trouble shooting manual is 500 pages thick and are sort of useless till you get the concept on how the DDEC works, the DDEC application manual is more help if you can find one

Hello,

I just downloaded it and have started the gripping reading.  I did buy that paper book on eBay that you or somebody said would help me understand the concept.  It is ok on concept, but useless on specifics as it is dealing with GM trucks, it looks like.

Anyway, this troubleshooting manual is quite comprehensive.  To get the lights to flash codes I am supposed to press a diagnostic button or something, but I don't know what or where that is.

At least I have something I can do now.  Today was quite frustrating since I didn't know where to start.

It seems to me that it could be a failing connection somewhere.  Of course those will continue to fail and get worse, and not better.

One other symptom or behavior I have noticed is that once it's all working and we hit the road it never causes problems thru the day, warmed up, etc.  In other words, when we stop for fuel or whatever, it always behaves.  This problem has only raised its head on cold start.

Don't know if that is a clue or not.

Thanks again

Seb

[Lee Bradley]

My DDEC II shut the engine off going down the road. Circuit breaker had given up ghost. No lights and cranked but no start. Replaced that breaker and hasn't missed a beat in seven years.

[buswarrior]

The procedure to get codes involves a switch on the dash, detailed in MCI materials.

You really, really, need to get a scanner for your electronic bus systems, one that will clear codes. You have both a DDEC III and an WTEC transmission to talk to.

A  busnut is a sitting duck at roadside without a means to read the computers.

You cannot be coached to a repair, without hard information.

The roadside pirates will liberate thousands of your dollars, for something you could have done for yourself.

Happy coaching!
Buswarrior

[Bill Gerrie]

Maybe Lee has an idea. When you get no lights on the dash use a voltmeter and check the circuit breakers to see if there is voltage on both sides. Failing circuit breaker is a potential problem you might have. No voltage to computer if will never start. You probably have a DDEC III but the DDEC IV is virtually the same. Just a little more upgrades. I have a DDEC III/IV troubleshooting guide (500 double sided pages) which I can get copied if you want to pay for it plus shipping. No idea of the cost. Next time you have lights operate every switch you have to see which one makes the CEL and SEL (red and Yellow lights) flash out any codes. Code 25 is 2 flashes and a pause then 5 flashes. 25 means all is okay. You have to have a switch (momentary type) that will make the lights flash. You can call me if you want at 905 873 8929  Bill.   

[luvrbus]

95% of problems with a DDEC is always on the OEM side the Detroit side of the ECM is usually good or bad,when people start cutting wires and removing OEM add on without delating those from the ECM you have problems.A Prolink will delete a few if they were preprogramed which most are not,your problem could be simple like the kneeling option and a scanner will not flash a code for OEM equipment.I have a stack of trouble shooting manuals for the DDEC and all I ever use is a blow up schematic of the Detroit responsibility  and the OEM responsibility, when the wiring leaves the ECM it is a OEM issue like a chassis computer if you have one on D3       

[azdieselman]

From your latest description, You may have an intermittent connection issue with your ignition switch. When it works you have no issues, but when you shut it off, and try and restart it, maybe yes, maybe no. It could be as simple as cycling the switch a few times to get going. That may work a few times for you. Good luck

[luvrbus]

When B&B would do a repowers on buses or rewires on a burnt Prevost,when you saw Van with 50 rolls of wire, bags of Deutsh pins and barrels business was picking up lol.Van made it look easy building a harness 3 inches around, I don't have that much patience but when he was finished it would fire off   

[RichardEntrekin]

Look on the right side of the DDEC unit mounted on the motor. It will have two plugs on the right side. Disconnect the upper plug. It's a bit tricky to get a flat blade in there and release the catch.
It's not the plug with the bolt in the center.

It's the same setup whether you have a DDEC III or DDEC IV.

When you get it loose, look at the wires on the back. Mine is easy, I have red and black. You can trace them into the plug. RED is hot, Black is ground. With the ignition on, check for voltage going to the computer. https://www.google.com/search?q=detroit+12.7+ecm+wiring+diagram&rlz=1C9BKJA_enUS846US847&hl=en-US&sxsrf=ALiCzsbBX9iEDRQNFlhaNJ3z73KqdbMFAg%3A1669162633407&ei=iWZ9Y-msGLafqtsP87WwkAE&oq=ddec+iii+wiring+diagram+pdf&gs_lcp=ChNtb2JpbGUtZ3dzLXdpei1zZXJwEAEYBTIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwAzIKCAAQRxDWBBCwA0oECEEYAFAAWABg6ERoAnAAeACAAQCIAQCSAQCYAQDIAQjAAQE&sclient=mobile-gws-wiz-serp#imgrc=Mt_eTPL6s-2shM&imgdii=q92QuMnvCRT6nM

Don't go flying by the basics. When you hear hoof beats, think horses not zebras. The intermittent nature of your problem does not indicate a failing ECM. When the check engine and stop engine lights don't come on, the first place to look is to see if the ECM is actually getting power. By checking at the power supply connection you will start a methodical process of finding the problem.

Now if it's not getting power, you start working backwards through breakers and relays all the way to the ignition.

When you say the DDEC lights up, are you talking about the PRO Driver display? If so, then it will show computer errors if you have them. It will not tell you that you don't have power to the computer, cause obviously the computer is not alive.

[Van]

Seb. Check you messages.

[Sebulba]

My DDEC II shut the engine off going down the road. Circuit breaker had given up ghost. No lights and cranked but no start. Replaced that breaker and hasn't missed a beat in seven years.

We'll, that was an easy fix, good on you.

Later post will explain my day

Seb