Hey guys got a quick question. Truck is dead, wont start but will crank,no juice getting to the LP, not cycling the grid heater. Pretty sure there is no 12v getting to the ECM from the key. Trying to track down my electrical short but its on a freightliner and all the wires are yellow and numbered. Does anyone have a schematic or just know which wire or wires is the power and the ground to the ecm off of the round connection by the LP. It would be a great help to know if I could sorta hot wire it for testing purposes to know that I am going in the right direction.

Thanks for all the help and this is a great site,
Jeff Ketcheside

 

i am thikin not a short, but a open like a main fuse blown, how ever I have no idea where your fuse box(s) are. On mine there is one on pass. above glove box, and an other in the wall next to the driver....The other thing is a disconected wire, maybe near the starter. Thats typical where everything is tied togather.

 

As far as I can tell everything else is working and the engine will crank over just no power to the ecm. Think I have checked all the easy connections now just gotta start tracing wire looms.

 

Jeff, is this in a busines class Freightliner? Your fuse box is located on the passenger side right below the dash.

I have every schematic you would ever need for a freightliner at home but I am not there so that doesnt do any good.

The ECM on your truck is a 100 wire ECM. The left side of the ECM is the OEM side. This is where you will be getting power to the ECM. The right side is the engine harness. First of all take an allen head socket and check to see if both ECM plugs are fully seated. (this screws in via the allen head bolt to the ECM) If you decide to pin out the ECM, be very careful not to force anything into the plug as it will spread the terminals. (sure wish I had my schematics here in front of me).


Back behind the fuel filter you will see a round cannon plug. This is the OEM bulkhead connector that ties into the ECM and just about every wire that runs to the engine compartment ties in here. There is also a VP44 relay located on the drivers side. It should be around the master cylinder if you have hydraulic brakes. If not, it should still be in that area. It will be by itself and comes from a leg of wire running from the engine harness.

 

Okay, I logged on to Cummins to get some info for you.

First of all, if the voltage was below a specific range for the VP44, you would be throwing Cummins code 366 with a PID of 1287. However, we will start at the pump.

The pump recieves its voltage from the pin 7 of the VP44 harness connector. The VP44 retrun or ground, is pin 6. Hook a multimeter up to pin 7 and 6. Turn the keyswitch on and check to see if you are recieving 6.5 - 13v. you are good to go. The threshold limit of the VP44 is more than 6.5v but less than 18v. Next, take your meter and switch over to Ohms, go from pin 6 (return) to a common ground with the key off. You should have below .02 Ohms. Next, with the key off and batteries disconnected, unplug the engine harness from the ECM and place your negative lead probe on the #7 pin of the ECM PLUG and place your pos. probe on the #7 VP44 harness cavity. You should also have below .02 ohms.

If everything falls into spec, you have eliminated the possibility of the VP44 harness. Which I doubt is your problem, but, still valuable info.

 

The ECM receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. There are three in-line 7.5-amp fuses and one 20-amp fuse in the unswitched battery wires to protect the engine harness from overheating. The ECM receives switched battery input through the vehicle keyswitch wire, when the vehicle keyswitch is turned on.

If supply voltage to the ECM falls below 6.5v. Fault Code: 434
PID: S251 will set.

 

This is about all I could come up with without my schematics. If you look at the last pic in my reply. The 23 pin connector is the OEM cannon plug behind the lift pump. Hopefully this has been some help. If you dont get the problem resolved. Please PM me, hopefully by then, I will have the schematics setting out in front of me.

 

Here is a good pic of the OEM connector. B, C, D, M, S will be your positve and E, F, H, P, W will be your negative. In this pic. They are testing resistance

 

Yes Monty this is a business class 99 FL60 Freightliner. Found the relay, its not doing anything and no power going to any of the terminal key on or key off also found a relay in the fuse panel under the right side dash, its the 2nd from the left on the top row that is also not doing anything, no power to any terminals key on or key off, I think if I could track down the power source to these relays I would find my problem. Called freightliner and there 10 days out on a service manual which is a bummer and there $350 but will still get one in the future. If you get a chance to get to your schematics and could fax or email them to me, depending on how many pages there are it would be greatly appreciated.

Thanks,
Jeff Ketcheside

 

No power to a relay ?? just run pwr to it........but,,i dont think that is it, would they be switching pwr on and off to the ecm ?????