DDEC II Toubleshooting M916a1

[RobertoGatos]

Experienced an intermittent power loss, then two shutdowns with the truck today. At first, the truck felt like the pedal became disconnected from the throttle. No power. Coasted to the side of the road, and truck continued to idle. CEL, and engine shutdown were lit. Shut it down, then got out to take a look. Everything seemed fine, gauges were all good. Couldn't see a problem.

Fired it up again, and took off. Felt just like normal, until a half mile down the road it did the same thing. This time the truck turned itself off, and I noticed the gauges and lights all went dead, then came back on all by themselves.

Was limping back home when it shut off again, and would not restart for 10min or so. During this time, the ignition key or battery switch would not power anything. No lights, no gauges, totally dead. The CEL and Shutdown light were lit before the truck turned off.

After that, I drove it home the last 10 miles like nothing was wrong. Seemed totally fine and ran great.

After reading through the DDEC portion of the TM's I can't seem to find out how to make the truck flash codes to the operator. Tried jumping pins A and M, then turning ignition on, and depressing the check engine button, but nothing happens. This seems tricky to diagnose without being able to get the codes. Any tips on that?

 

[RobertoGatos]

No luck, so I took it to a Kenworth shop that has scanner, at least they should be able to get some codes for me. Will know more on Monday hopefully.

 

[wrenchturner6238]

This kind of sounds like to me you are loosing connection to the battery be it a ground or power. I think i remember that freightliner went from bat ground to frame then from frame ground to components for a few years. I would start of by taking all the connections apart and clean them for sure at least all the ground connections.
I do not recall any way to get trouble codes out of a DDEC without a reader but always had a reader to use where I worked.

 

[RobertoGatos]

This kind of sounds like to me you are loosing connection to the battery be it a ground or power. I think i remember that freightliner went from bat ground to frame then from frame ground to components for a few years. I would start of by taking all the connections apart and clean them for sure at least all the ground connections.
I do not recall any way to get trouble codes out of a DDEC without a reader but always had a reader to use where I worked.

Thanks, will give that all a once over. Might have missed something somewhere...

 

[wrenchturner6238]

I will say this too. I take all my ground connections off and polish to nice clean metal and clean the wire end and i get rid of the star washer.

 

[RobertoGatos]

Update, picked the truck up after having the codes read and cleared. They were all inactive, and seemed pretty benign. They were: engine overspeed, fuel temp. too high, and ECM voltage low. Going to check all the connections for corrosion, and find out more about these faults.

 

[NDT]

ECM voltage low is the key one. Somewhere between the batteries and the ECM, there is an intermittent connection. I would start at the battery box, cleaning and verifying all the connections.