M1078A1 decided to go crazy today.

[JRKJeeper]

Well I guess when you fix one the other one starts to go nuts.... My 1078A1 has been running fine. Today after sitting away I went out for a ride and it went into 5 and check trans came on. IT would reset when I stop and then as soon as I start driving go back to check trans an #5. Codes in trans control are D!-1323- which i found to be overvoltage, D2- 4413 ground issue, D3-4226 unknown. I check battery cables and they seem to be ok. I lifted the cab and found the alternator is flashing from a green 14v to a super fast green red flash under 28v. Also when I turn it off and back on everything is dead. After 5-10 min it comes back to life where I can start it again. Cable connections seem good. When it came back to life I drove it a few miles and it was fine then it went back to codes. Not much help in the neihoff trouble shooting. But the fact the whole dash goes dead for awhile is puzzling me.

 

[JRKJeeper]

left it off awhile with the disconnect turned off. Turned it on and back to 2 green flashing on VR. Cleared codes. Went to drive and the first shift was stiff then back to the check trans, #5 on push button and now a code 42 12

 

[MatthewWBailey]

https://thecampingadvisor.com/allison-transmission-fault-code-list/

I've used this for trans codes. There may be another more specific list for lmtv but this is Allison's. 4212 is solenoid shorted to battery, seems like wiring issue.

I have/had the same trans shift to 5 problem. Same overvoltage codes. I have overvoltage issues on my alt which can cause the trans fault. Mine were trans connector (cleaned) issues and a bad alt. I've been told The wiring on these trucks can be suspect/damaged due to their previous life.

there's a link in the FMTV TM section above to download the electrical schematics for the A1. These are great and you can troubleshoot with them. Must have.

The dead panel problem possibly starts with the ignition relays k1 and k2. If those are off (within PDP on passenger side dash panel) then start there. Maybe a bad manual disco terminal too.

 

[MatthewWBailey]

This thread may also yield some direction..read Ronmars post

https://www.steelsoldiers.com/threads/m1078-lbcd-and-transmission-shifting-problems.218490/

 

[JRKJeeper]

Checked all the connections along the trans harness last night. Was hoping to not have to pull it all out to check for bad wires as this one doesn’t seem to be brittle yet. This morning worked fine for 25 miles. So I’m guessing it was one of the connectors.

 

[JRKJeeper]

New one now... Moved it to change the tires and now it doesnt power anything on when I hit the switch. It smells like something might have burnt under the PDP. I opened the panel below and nothing looks bad. I guess I need to take all the screws off the PDP to lift it out and look at the back of the board. I know there can only be a few breakers that would stop it from powering anything on. Should the 24v bolt in the PDP read 24vt as long as the disconnect is on? All of the cables look good going from the battery up to spare and than over to the alternator. I just replaced the batteries a month or two ago. But after swapping 10 tires... swapped the 1078 tires to the 1083 so I think this is a job for tomorrow.

 

[Ronmar]

A1 panel has 4 bolts in the PDP. 12 and 24v battery and 12 and 24v ign. With the battery disconnect switch on, the 12 and 24 bolts should have 12 and 24. When you turn on the ignition switch, the 12 and 24 from the battery bolts should be connected to the 12 and 24 ignition bolts by the two ign relays located under the PDP. 3 screws up under the lip toward the windshield, and 3 screws in front of your knees when seated and the whole PDP should lift out and flip toward you to get to the underside…

 

[hike]

New one now... Moved it to change the tires and now it doesnt power anything on when I hit the switch. It smells like something might have burnt under the PDP. I opened the panel below and nothing looks bad. I guess I need to take all the screws off the PDP to lift it out and look at the back of the board. I know there can only be a few breakers that would stop it from powering anything on. Should the 24v bolt in the PDP read 24vt as long as the disconnect is on? All of the cables look good going from the battery up to spare and than over to the alternator. I just replaced the batteries a month or two ago. But after swapping 10 tires... swapped the 1078 tires to the 1083 so I think this is a job for tomorrow.

R12 or R13? is under the PDP; the other R13 or R12 is under the cab below the fuel/water separator. Both are in the J1939 circuit and connected to the ECU/ECM's for CTIS, engine, and transmission. Most likely thing in my limited experience to burn up under the PDP. If one is gone likely the other is, too.

 

[JRKJeeper]

A1 panel has 4 bolts in the PDP. 12 and 24v battery and 12 and 24v ign. With the battery disconnect switch on, the 12 and 24 bolts should have 12 and 24. When you turn on the ignition switch, the 12 and 24 from the battery bolts should be connected to the 12 and 24 ignition bolts by the two ign relays located under the PDP. 3 screws up under the lip toward the windshield, and 3 screws in front of your knees when seated and the whole PDP should lift out and flip toward you to get to the underside…

I ended up messing with it again tonight. When I took a reading from the 24v battery bolt on the PDP and to ground it was low. like 13v but it would slowly climb to 24.4v after 90 or so seconds. Then when I flip the power switch it would power up for a second and then go out. The process of the climbing volts would then restart. So I went and tested at the disconnect and it had good voltage. So I gave the two relays in the disconnect box a couple of whacks and then I got the voltage back. Back to running like it should.

 

[GeneralDisorder]

I ended up messing with it again tonight. When I took a reading from the 24v battery bolt on the PDP and to ground it was low. like 13v but it would slowly climb to 24.4v after 90 or so seconds. Then when I flip the power switch it would power up for a second and then go out. The process of the climbing volts would then restart. So I went and tested at the disconnect and it had good voltage. So I gave the two relays in the disconnect box a couple of whacks and then I got the voltage back. Back to running like it should.

The disconnect relays are a known issue. Cooper-Bussman makes a fully enclosed replacement:

Cooper Bussmann EMS300-1224-D-00 Battery Disconnect for sale online | eBay

Find many great new & used options and get the best deals for Cooper Bussmann EMS300-1224-D-00 Battery Disconnect at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[hike]

The disconnect relays are a known issue. Cooper-Bussman makes a fully enclosed replacement:

Cooper Bussmann EMS300-1224-D-00 Battery Disconnect for sale online | eBay

Find many great new & used options and get the best deals for Cooper Bussmann EMS300-1224-D-00 Battery Disconnect at the best online prices at eBay! Free shipping for many products!

www.ebay.com

We bought this last fall and have already removed it along with our LBCD as we replaced our dual alternator with a 24v 200a unit. Looking to sell our lightly used disconnect. PM if interested—

 

[MatthewWBailey]

It's a dumb thing to begin with. I like the whack-it fix thou. I'm going to see if mine fits in the potato gun and give it a military salute.