ddec 4 goes dead randomly

Really need some help. Yesterday while driving truck "blipped" a couple times. A couple minutes later it went dead stick for a few seconds like you turned off the key. All gauges read normal no lights except for engine can on. When the engine can light went off the truck would come back to life and repeat. I was able to duplicate the symptom with the engine off as well. Would start but not crank unless the engine fan light was off. When truck is off it would flicker between the normal dummy lights at startup and engine fan on.
Checked every connection unplugged every sensor an felt and shook every wire on the harness without and positive duplication of symptom. Then removed ecm and had checked, they said it checked out ok off truck. Re installed and symptoms are much more spread apart, enough that I'm back running today but still highly concerned.
Hopefully someone has had a similar problem, thanks

 

Also truck is a 1998 peterbilt 377

 

the ecm is cooked. (4) 5/16 12 point bolts in each corner, 1/4 bolt inside harness to remove. See if something fell between ecm and block and rubbed through back of ecm.

 

Well I took it off and a shop tested it and said it was ok, he did say the noise from the truck could make it act different though. May be a good time to get Erich Owens to soup me one up I guess

 

Always suspect wiring and connections first over blaming a bad ECM. ECM's are tough and rarely fail. Replace it as a last resort. I recommend to run the engine and then start wiggling the wiring harnesses from the batteries up to the engine and from the engine to the cab. Hopefully it is just a wiring problem and you can find it by the 'ol wiggle test.

 

I absolutely agree I did that for about 8 hours yesterday and could never reproduce the symptom per a single wire. Truck ran for about 14 hours today and only shut off once about an hour into the day. Guess when it strands me I'll have to figure it out

 

Definitely looks like a power issue.

 

I've got a 1999 379EXHD w/a DDEC IV. I had something like the problem you describe. After much labor, testing everything we could think of, we decided to replace the main cab wiring harness. $3500 later, that was NOT the problem. Another 40+ hours of time invested by my repair shop & they were baffled. The problem was, regardless of what they did, they could NOT get the "switched" side of the fuse panel (right side) to power up. It had been intermittently before but just quit totally. What the problem finally discovered was the 31 pin firewall to ECM harness was bad. By that I mean, there were 12 wires that split off in a separate "loom" & went under the cab. This was were the factory screwed up!! INSTEAD of running the 12 wires through the INSULATED loom clamp, they simply layed them OVER the bracket that held the clutch switch. When the cab air bags lost air pressure after a few days, the cab would come to rest ON TOP OF THE #### WIRES. After all these years 7 of the wires to cut through and the rest were rubbed down pretty badly. Greg (my mechanic) did a quick repair to all the wires & VIOLA, the truck ran perfectly. THAT wiring harness cost me another $1400. But it solved the problem.

 

Thanks I'll look for that harness

 

most problems like you have, are the cause of a bad ground. (somewhere) I hope this helps you.

http://www.ddcsn.com/cps/rde/xbcr/ddcsn/1-SECM-03-03.pdf
http://ww2.justanswer.com/uploads/ClaytonH729/2010-12-31_005346_31477.png

http://ww2.justanswer.com/uploads/CL/ClaytonH729/2013-08-15_214549_ddec34engineharness.png
http://constructiontractors.tpub.com/TM-9-2320-302-20-2/TM-9-2320-302-20-21079im.jpg