Master switch no power

[Jcparmley]

I have 24 volts at stud 24 and 25 in rear panel

I have 12 volts going through the DDEC 6 amp breaker

I have 24 volts at stud 53 and 54 of the rear panel

I have 12 volts at stud 4 on the front DDEC Board

ECM schematic is 7L-13-1580

If you have no power to the ecm fuses (there are 3 of them) then your wiring is wrong at the batteries. If you have power there then proceed and check the following...

You already determined you have a bad breaker feeding the main switch, so either fix it or temporarily bypass for the purpose of proceeding with the testing.

With the main switch on, check for power on stud 14 in the front box. From there power goes to the rear juction box stud 24 and 25. From stud 25 to main bus bar via wire 3-BK-14, through a 6 amp breaker, then to stud 53 via wire 6-BL-16, then to the rear engine run switch and then to remote control box horizontal stud 9 then back to rear junction box stud 54. Stud 54 then feeds the ddec relay via wire 6A-BL/YL-16. The relay feeds the 12v diag ports and the ecm, and power for the indicator lamps.

Are you thoroughly confused now? To put it in simple steps, first make sure the rear start switch is set to front and the run switch (remote control box in the engine bay) is set to run and not off. Turn on the main switch and check for power on stud 14 front box. If you have power there and everything is as it should be check for power on the ddec stud 4 in front junction box.

[daddysgirl]

Just FYI...This is a good basic guide to work from that you can print with the more specific guide. The first few checks you've already done. There is also a number for MCI if you need it. They will walk you through further checks (like the NSS) if necessary.

http://www.mcicoach.com/fyiFromMci/maintMatters/0514.htm

EDIT: Also, if you want to check if the starter solenoid is bad, with the master switch on, put a jumper between the two large studs. This acts as a starter switch, but it might spark a bit.

[Jcparmley]

Thanks

I read through that and have done all the checks.  I also tested the starter solenoid and it cranks but won't turn over.  It must be the ECM.  However, I have checked for power at all the correct places.  Very frustrating.

Just FYI...This is a good basic guide to work from that you can print with the more specific guide. The first few checks you've already done. There is also a number for MCI if you need it. They will walk you through further checks (like the NSS) if necessary.

http://www.mcicoach.com/fyiFromMci/maintMatters/0514.htm

EDIT: Also, if you want to check if the starter solenoid is bad, with the master switch on, put a jumper between the two large studs. This acts as a starter switch, but it might spark a bit.

[Jcparmley]

Sorry Derrick

I missed the question of what year the bus is.  It's a 96.  The ECM is on the right side of the engine?  I must be missing it. 

[daddysgirl]

You might have a different version of this ECM wiring diagram, but I wasn't sure. The others will tell you if it won't help.
The wiring should be pretty much the same.
https://www.wanderlodgeownersgroup.com/downloads/DDEC_III-IV/2011-10-07_013933_DDEC_II_Wiring.pdf

[Jim Blackwood]

What's this business with the step light switch?

Jim

[daddysgirl]

What's this business with the step light switch?

Jim

It's a theft deterrent. If the step light switch needs to be on or the engine won't start.

[thomasinnv]

You have power in all the right locations. Only thing left is to check for power at the ecm itself. Open the curbside (passenger side) engine access door and look on the side of the engone block just above the oil pan. Big metal box with wires plugged in. The big plug on the right side is what I believe you need to access. There is a bolt in the middle of the plug. You are checking for power on 3 pins and ground on I don't remember how many. Clifford could probably tell you what to do in his sleep. The ecm schematic I referenced in an earlier post shows what pins you are looking for. If you reversed the 12v positive and negative cables at the batteries in your previous steps you quite possibly fried the ecm. Too bad I'm so far from you,  I have a spare ecm and programming capabilities.

[Jcparmley]

Ok, let me check there.

You have power in all the right locations. Only thing left is to check for power at the ecm itself. Open the curbside (passenger side) engine access door and look on the side of the engone block just above the oil pan. Big metal box with wires plugged in. The big plug on the right side is what I believe you need to access. There is a bolt in the middle of the plug. You are checking for power on 3 pins and ground on I don't remember how many. Clifford could probably tell you what to do in his sleep. The ecm schematic I referenced in an earlier post shows what pins you are looking for. If you reversed the 12v positive and negative cables at the batteries in your previous steps you quite possibly fried the ecm. Too bad I'm so far from you,  I have a spare ecm and programming capabilities.

[Jcparmley]

Ok, I checked the harness plug for the ECM and I do have both 12 volt and 24 volts on various pins.  I checked them all because I didn't have a schematic in front of me.  So does that mean that the ECM is fried?  I am certain I have the cables correct in the battery bay.  Perhaps it shorted or something when installing the batteries.  Now what do I do?  Can the ECM be rebuilt?

I don't know if this matters but when I turn on the main switch in the battery bay and before I turn on the main switch on the dash I hear a faint beeping in the front J Box.  I'm not sure where it's coming from but it is there.  It' probably nothing.

[6805eagleguy]

Looks like a rebuilt ddec 4 runs about $1500

https://truckecm.com/product/detroit-diesel-ddec-iv/?gclid=Cj0KCQjw2IrmBRCJARIsAJZDdxBuVBULv0gp7uzi2F5xeF47wibH-i8xtkZJ45aJpqfYIQeEuJCHb6kaAv1tEALw_wcB

[daddysgirl]

I don't know if this matters but when I turn on the main switch in the battery bay and before I turn on the main switch on the dash I hear a faint beeping in the front J Box.  I'm not sure where it's coming from but it is there.  It' probably nothing.

Is this beep a new symptom? Can you hit the battery switch on, go around and see what is beeping?
I might be the lone hold out...but I was thinking this is something simple.

[Jim Blackwood]

Actually it probably is something but let's stay on task. JC my bus is also a '96 and may be close to yours on the production number. My VIN is 48598, you haven't said what yours is that I've seen. Anyway a few quick notes: First, on my bus it doesn't matter if the stairwell lights are on or off the bus still starts anyway. That could have been defeated or could have come that way.

I'm attaching photos of the battery bay. You should be able to blow them up large enough to compare the wiring to your own. If everything matches move on. If anything doesn't, first identify what it is and don't make changes until you are certain they are going in the right direction.

I have a photo of that big sucker above the Vanner if you need it, likewise one of the yellow remote box in the engine bay. I think only the two switches on the right can keep it from running though and they are pretty self explanatory.

Let me know what else you need.

Jim

[Jcparmley]

No it's not a new symptom.  I have tried to locate the beeping but have been unable.  It's not loud like the one that beeps until the bus airs up.  It's real faint but definitely present.

If the pos and negative were flipped wouldn't my voltmeter read -volts? 

Is this beep a new symptom? Can you hit the battery switch on, go around and see what is beeping?
I might be the lone hold out...but I was thinking this is something simple.

[Jcparmley]

Hi Jim

Can you send me the one of the back remote bloc.  When I opened it today I found one lead not connected to anything.  Don't know if it's anything but that could help.  I looked at the schematic but couldn't find it.  Thanks

Actually it probably is something but let's stay on task. JC my bus is also a '96 and may be close to yours on the production number. My VIN is 48598, you haven't said what yours is that I've seen. Anyway a few quick notes: First, on my bus it doesn't matter if the stairwell lights are on or off the bus still starts anyway. That could have been defeated or could have come that way.

I'm attaching photos of the battery bay. You should be able to blow them up large enough to compare the wiring to your own. If everything matches move on. If anything doesn't, first identify what it is and don't make changes until you are certain they are going in the right direction.

I have a photo of that big sucker above the Vanner if you need it, likewise one of the yellow remote box in the engine bay. I think only the two switches on the right can keep it from running though and they are pretty self explanatory.

Let me know what else you need.

Jim