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Topic: Bad DDECII Unit? (Read 695 times) previous topic - next topic

Bad DDECII Unit?

I am trying to diagnose why I can't start my coach.  When I turn the key, the lights on the dash all come on, BUT unlike normal they all stay on and don't turn off.  No codes will flash.  Fuses have been checked and all are good.  Will crank.  Fuel is not being delivered.

I have started and driven this coach very little over the years, but it has always started very easily even when cold.  I took the DDEC II unit 250 miles away to my nearest Detroit Diesel service center.  They said over the phone that they would be able to check to see if the unit was still working.  Well, after I arrived I was informed that they had made a mistake and that they could only test DDEC II while in the coach.  I am not having my coach towed 250 miles. 

I have asked local shops if any of them have a DDEC II Pro Link reader.  Only 1 shop has one and they said they are too busy to waste their time coming out to my coach and they were unwilling to loan it to me.

I can buy a scan tool if I need to.  Not sure what to get.  Won't do much good if the module has gone bad. 

I am open to any thoughts and/or suggestions.  Thanks in advance!

1988 Grandvilla UniHome 40'
6V92TA DDEC Silver Engine

Re: Bad DDECII Unit?

Reply #1 –
Last winter my coach wouldn't start and it turned out that not enough power could get to the
ECM. I had used a test light and it lit up but I should have used my test light I made up using
a halogen head light bub and I would have found the problem.  The problem turned out to be
a corroded connection.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Bad DDECII Unit?

Reply #2 –
DDEC ECMs have a low failure rate but like most ECMs, they are sensitive to low voltage. Many components don't like sitting idle for month after month or year after year. You need to make sure you have full engine battery voltage when you try and start the coach but before that, pull and clean all the battery terminals and any other battery connection points. Solenoids are also sensituve to corrosion in the connections and inside too. Do you have the 12V schematic for the coach? DDEC schematic too.

And yes, a ProLink 9000 would tell you what the voltage is to the ECM.

If you can't drive the coach much, you should probably sell it as there will likely be more problems down the road.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Bad DDECII Unit?

Reply #3 –
You will need a ProLink with the Dedec 2 cartridge to diagnostic test.
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921

Re: Bad DDECII Unit?

Reply #4 –
My '91 had an issue where it would crank but not start. The radiator has a low coolant level sensor on the top of the radiator. If your coolant is below that sensor the engine will shut down if driving or won't start.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Bad DDECII Unit?

Reply #5 –
Quote from: prfleming –
My '91 had an issue where it would crank but not start. The radiator has a low coolant level sensor on the top of the radiator. If your coolant is below that sensor the engine will shut down if driving or won't start.
Excellent point. A member had this in the past but the coach was backed up to a wall so the engine door could not be opened.

P
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Bad DDECII Unit?

Reply #6 –
I am also dealing with DDEC issues.  The coach runs fine.  I get codes using the under dash switch but the Prolink does not see the codes to clear them.  I know the computer is communicating with the Prolink, but just not the codes.  The Prolink keeps telling me to use a DDEC I & II cartridge instead of the DDEC II & III cartridge that I'm currently using.  I'm thinking about a computer rebuild.  Sorry ForeFam, not trying to hijack your thread, just wanting to share your pain dealing with these antiquated ECMs. 
Jeff & Lisa
"Optimus"
1990 GV - #3605
U300 Unihome
6V92 Detroit

Re: Bad DDECII Unit?

Reply #7 –
Quote from: oldguy –
Last winter my coach wouldn't start and it turned out that not enough power could get to the
ECM. I had used a test light and it lit up but I should have used my test light I made up using
a halogen head light bub and I would have found the problem.  The problem turned out to be
a corroded connection.

I have tried a test light, thanks for the idea on using a head light bulb for more sensitivity.  I will dig out the multimeter.

Quote from: Pierce & Gaylie Stewart –
DDEC ECMs have a low failure rate but like most ECMs, they are sensitive to low voltage. Many components don't like sitting idle for month after month or year after year. You need to make sure you have full engine battery voltage when you try and start the coach but before that, pull and clean all the battery terminals and any other battery connection points. Solenoids are also sensituve to corrosion in the connections and inside too. Do you have the 12V schematic for the coach? DDEC schematic too.

And yes, a ProLink 9000 would tell you what the voltage is to the ECM.

If you can't drive the coach much, you should probably sell it as there will likely be more problems down the road.

Pierce

Batteries have enough charge to crank this beast like a pro, and voltage checked as well.  Will check voltage at ECM.  The previous owner did have schematics but the schematics are for a different year.  Everything I've referenced the schematics for in the past have been the same though.  No intention to sell at this point.

Quote from: Andy 2 –
You will need a ProLink with the Dedec 2 cartridge to diagnostic test.

I see plenty of Prolink 9000 units and DDEC II cartridges for sale on ebay.  However, I don't know what the connector is called.  I don't see any DDEC II cartridges being sold with a Prolink 9000 so I assume I will need to buy the connector cable separately. 

Quote from: prfleming –
My '91 had an issue where it would crank but not start. The radiator has a low coolant level sensor on the top of the radiator. If your coolant is below that sensor the engine will shut down if driving or won't start.

I was aware of that as well.  Checked.  This wouldn't cause all the test lights to come on and not turn off though, but I appreciate you making sure I was aware.

Quote from: Jeff M. –
I am also dealing with DDEC issues.  The coach runs fine.  I get codes using the under dash switch but the Prolink does not see the codes to clear them.  I know the computer is communicating with the Prolink, but just not the codes.  The Prolink keeps telling me to use a DDEC I & II cartridge instead of the DDEC II & III cartridge that I'm currently using.  I'm thinking about a computer rebuild.  Sorry ForeFam, not trying to hijack your thread, just wanting to share your pain dealing with these antiquated ECMs.

No problem.  Hopefully we both find solutions that work.

Thanks to everyone.  I guess looking at voltages at the ECM and ordering a Prolink 9000 and DDEC II cartridge is next on my list of things to do.
1988 Grandvilla UniHome 40'
6V92TA DDEC Silver Engine

Re: Bad DDECII Unit?

Reply #8 –
Might try to isolate the start battery and run the ecu from another source. 

Re: Bad DDECII Unit?

Reply #9 –
In My sales manager training with Detroit back then I was told that the DDECll would run on low voltage
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Bad DDECII Unit?

Reply #10 –
Life got in the way and I still haven't resolved this.  Just getting back to it now. 

Does anyone know what pins on the DDECII connector I would check for the level of voltage that the module is getting?
1988 Grandvilla UniHome 40'
6V92TA DDEC Silver Engine

Re: Bad DDECII Unit?

Reply #11 –
These might be helpful
1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

Re: Bad DDECII Unit?

Reply #12 –
Check the ECU fuse under the dash first.Make sure it has power across it. Inside your battery cargo bay to the left is a cover on the divide wall.  Take that cover off there're fuses there that supply voltage to ECM.  Check voltage across both fuses. These 2 fuses are fed from the fuse in the front dash. Start there and post results.
One fuse powers the left bank of cylinder and the other the right bank. But both are supplied from the one in the front.
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: Bad DDECII Unit?

Reply #13 –
Quote from: Caflashbob –
In My sales manager training with Detroit back then I was told that the DDECll would run on low voltage
It will run on low voltage but when you engage the starter, the voltage drops WAY down especially if the voltage is down a little. Just before I replaced the engine batteries, I had our coach not start until I put a charger on for a little while. If the engine turns over quickly when you go to start it, it most likely has plenty of volts. But, check the fuses as posted above. A Prolink will show the DDEC voltage.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)