2000 7,3 no check engine/wait to start

[SimonSEZ]

I have a problem on an E450 2000. The engine die after running couple of seconds.
The check engine and wait to start light won't even come on when turning the key to run. The scanner won't communicate with the ecm. I've search and the only thing I found about this is the fuse of the ecm often blow because of a shorted fuel heater. All fuses are fine, and make some pin point test on the ecm and it has all is power and ground...

The ecm relay is working but the fuel pump and the IDM are not getting the ground signal from the ecm. Found a used ECM for 100$ even if I was pretty sure that this was not the problem.... and it do not solve anything.
Check the ignition switch, the diagnostic connector, the inertia fuel cut off swith(as not 12v because of the IDM). Un plugged every related connector searching for rust. Notice the ecm is getting hot??

I'm pretty sure I'm missing something basic, I'm more qualified on gasoline engine. The ECM seem not receiving the ''ok'' from something to turn on... I have acess to wiring diagram from alldata but did not find anything.
A little help would be appreciated, thanks!

[NoRalPh]

I'd first verify the supply of power to all the pins of the PCM connector it's supposed to have (SO OFTEN it's a supply problem from fuses that either "look" good, or are making a poor connection in the fuseblock - especially #30-19-22).

Then, if it all checks out, I'd bite-the-bullet and go for a PCM

Also, is there any kind of a chip in the truck? If so, TAKE IT OUT!

[Chuck stallions]

I've been bitten by the blown fuse that was broke in the corner everyone always look at the middle even me best thing is to ohm the fuses

[SimonSEZ]

I've already try an other ecm, with no sucess. I've checked all the fuses at least 5 times. Even replaced them.... but has I said.... The Ecm has all his power and ground .... but it seem like it miss something to turn ''ON''.
For the check engine light, I have battery voltage at the pcm but It's not giving the ground.
The truck has no chip...it's a school bus! but

[NoRalPh]

Power & Ground (those that actually run the PCMs electronics) are supplied to the PCM in MANY places, you need to know they're All there.....

Go to Alldata and get the pin-out of that PCM plug.

[SimonSEZ]

That's done, have gone tru the complete pin out of the ecm connector without finding anything. Double check everything. Look like the ecm his dead ....but 2 ecm having the same problem... seem impossible to me.

[SimonSEZ]

I found the problem friday, even if the fuse was ok , I've decided to take a look at the fuel heater... beginning by removing parts et unplug some connector...taken a look at the instrument cluster and my check engine and wait to start was working!!! so begin re-assembling parts by parts...and the problem was the exhaust backpressure sensor.
If I plug it, the check engine light disappear. I tested the sensor and one pin have 5m ohms of resistance to the tread of the sensor...so it's short to ground. I do not understand why it shut down the ecm but at least it work!

[reinaldo]

If that is the case, I think it would be better if you're going to replace the fuel heater to resolve the problem. If by chance there is a need to replace some parts, I suggest you visit car parts online.com.