Engine/Transmission (1998.5 - 2002) No Bus or gauges. Lift pump runs constantly.

[stacerbob]

Let me start at the begining, I am fairly new to the diesel game. I bought this truck wrecked (99 3500 Auto)so I could rebuild it and have a bargain Cummins. I have most of the repairs done and am ready to start it.

When I hook up the batteries,

The lift pump runs-key off and when I turn the key on, the odometer reads the mileage, then chimes and reads No Bus. The gauges(mostly the fuel) slightly raise, then drop every few seconds. this coincides with the wait to start light and brake light getting brighter and dimmer. These lights continue this even with the key off. I have the LP unplugged and a test light in place so as not to "cause" any damage.

It had about 4-5 wires smashed under the left corner of the intercooler, I never paid any attention to what they were for, I snipped them one by one and replaced about 2-5" of them with wire of the same gauge, it also had 2 wires broken in the harness that runs over to the engine from the PDC.

I am suspecting that the ECM is toast. I have a guy that I know at the dealership that has loaned me the factory service manual.

What do all of you experts think? Where do I start? Would I be better of doing the P conversion? And if so what do you do for the gauges when you do that conversion.

I am not looking to bomb this truck(yeah right!) I just want to get it going and make it dependible. My TT weighs about 9500lbs and my BB suburban gets about 3-4 MPG pulling it. Thanks for your help in advance and if you read all of this rambling!!

Stacy

 

[Marco]

stacerbob,



To answer your question, I don't think the ECM is bad. Most likely you have a short or smashed wire(s) somewhere.



Reason I say this is because you mention that the wait to start light comes on. Now the ECM runs a self test every time it's powered up. Problems with the software, flashing wtsl. Problems with the ECM itself, no wtsl at all.



Maybe these links provide a more readable layout of the ECM and it's circuits than the repair manual.

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If you need further help just shoot me a line.



Marco

 

[stacerbob]

Marco, I was doing some more looking tonight at wires and such, after about an hour I looked inside and the WTSL was not on, not even dimly like it was with the key off. I did the self check of the cluster again and the light doesn't come on???

 

[A Johnson]

Make sure you don't have any moisture in the ECM connection. Water can cause all kinds of funny problems.



A Johnson

 

[Marco]

ECM test.

The ECM can be tested.



Pins 5 and 50= 12 Volt

Pin 30 = Ground

Pin 37 = Wait to start light.



Pin 37 turns on the ground circuit for the light. With a tester check the voltage between pin 37 and the 12V power supply.



When you feed power to the ECM there should be a voltage reding for a few seconds on pin 37. ( WTSL light comes on and then out)

If it does so then the ECM is OK.



The triangle shaped connector for the Cummins bus works with or without the dust cap on it. To get a correct reading from there you need a J 1939 bus analyzer. Thats's beyond what you need to do.



Marco

 

[DMC]

It could be that you possibly have more than one fusable link in your electrical system. No Bus is probably telling you that you have no power to your PCM. If you dont have a shop manual it will be hard to diagnose the electrical system. I would imagine the smashed wires you mentioned are a good place to look. A fusable link is a wire that looks normal except in the line it has an overlay of shrink tubing. Under that is the weak link designed to short out in the event the positive side of your electrical system going to ground and thus prventing a fire. Trace all of your electrical connections from the hot side of your left battery.



Thats my best guess.



Anyone Else!!!!!



Good Luck



Don