2005 Peterbilt 378 Wiring Issue

[Hunter013]

1XPFDB0X05N860710 C-15: MXS09731

We've been having this problem for a couple of weeks now. Truck will shut off like you shut the key off and because its rolling it will start right back up. The dash loses all power as well. Driver says it usually start to happen after he's running through the landfill loaded. There has been a couple times where the driver pulled off and it wouldn't start until he wiggled some harnesses and then it started. Other times the fuel guages will show full or empty when they are not. One/a few times the driver said after it restarted by itself, the truck accelerated by itself. Some times apparently it will shut off and then crank but not fire. No codes are logged. The driver said one time when it shut off it flashed the CEL 6 times. We've spent probably 2 days total looking over all the harnesses and connection and cant recreate the issue in the shop.

 

[Truck Shop]

With what your describing, several different circuits-but starting by it's self and accelerating?
I think a cab camera would be useful.

 

[Hunter013]

This issue is starting to occur more frequently now. The symptoms now are that the truck will shut off by itself while driving and start itself back up within a few seconds, while its still rolling. Recently it has shut off while he's sitting at idle or driving at idle speed. Then when he tries to fire it back up, it will crank but not fire. He said the last time he let it sit for 5 minutes, didn't wiggle any wires or anything, and it fired right up. I just checked power supply and grounds to the ecm and everything checked out. I have never been able to look at the truck while its actively not starting. We had a problem before where a cable from the battery to the starter was rubbing on a cross member, but since then we wrapped and tied up a lot of hoses/wires. I could not see any rubbed spots when I went under the truck today.

A while ago I did set up test lights just before and after the large auxiliary relay behind the dash and the driver says both lights stay lit up when it dies so I assume its wiring from there to the ecm.

Being an intermittent issue, what should I check first?

 

[Norcal wrench530]

How are you Batteries? have you load tested them? I had a freighliner cascadia do similar things (shut off while going down the road and firing back up) I started paying attention to the battery voltage... it would hang out at 14.2 then drop down to 11 and the truck would shut off, the ecm grounds were corroded and one battery was bad, i wanna say the alternator was on its way out as well, the one the main connections went to. truck went to a shop 3 times and they didnt find anything, but it seemed like they didnt look to hard. Its very irritating being intermittent

 

[4x4ford]

Check all of your battery connections do a tug test on all of them especially any smaller wires that would be live power to ecm

 

[Hunter013]

In the battery box, I found the ecm power and grounds. I pulled on every connector and followed it all the way up to the ecm while it was running and never got it to shut off. The negative connector to the battery had some play in it, but no matter what I did, it wouldn't shut off. I replaced the connector and I am having the driver take it today and i'll see what happens.

Batteries all tested great. The positive and negative for the ecm were on different batteries, so I put them on the same battery as well.

 

[Truck Shop]

ECM

 

[Crummy]

Did you flip the tach/speedo panel and check the grounds on the bulkhead stud?

 

[Truck Shop]

Heat.

 

[Hunter013]

Heat.

Can you elaborate?

 

[Hunter013]

Did you flip the tach/speedo panel and check the grounds on the bulkhead stud?

I did not. I only set up test lights off the power and grounded them to whatever chassis ground was near. I will look at that stud.

 

[BAY ONE-SEVEN]

The Ignition breaker. (20a Push Button)
I had a bad connection on the back of the fuse panel to the Ignition breaker.
Moisture had gotten in there and corroded the connection.

Please let us know what you find. I enjoy these types of problems.