99 ranger 2.5 wont start. It does not have fuel pressure and I can not hear the pump run. The spark plugs are not firing and the creader reader only comes up with the letter E. Thought maybe the PCM was bad but the junk yard replacment does not do anything different. Turns over just fine.
Where\what to check?

 

Did this problem come about after some event????

Your likely on the right track suspecting the comuter, as it controls the spark & fuel injection, but the computer itself may not be the root cause.

Maybe begin with checking the B+ feed to the computer.

When you turn the ignition key from off to run, before cranking the engine, do all of the warning lights on the dash light up for their system self check????

If not, maybe begin with a check of the under hood computer power relay, located in the power distribution box, drivers side back where the firewall & fender meet. These relays are a common problem part.

You could give it a thump to see if it'll wake up, or swap it for a like relay not needed to run the engine, like the AC relay & see what happens.

Check for blown fuses to the computer & power relay too.

Let us know what you find.

 

All the warning lights do not light up. I will check the relay.

 

switch PCM power rely with the starter rely No change and it still turns over.
So the PCM rely is good

 

Check fuse number 8 in fuse box under hood it is power for the pcm relay. Nothing is going to work until the pcm has power. Number 6 is pcm memory

 

Checked fuse 6 and it looks good . Replaced it anyway, nothing same symptoms. Checking wire harnesses for any type of damage.
I got to be missing something.

 

OK, good trouble shooting so far.

Now check the PCM relays power diode, if you have one it'll be in the under hood power distribution box.
With your multimeter set on the X1000 or higher ohms scale, It should show continuity in only one direction when the multimeters test leads are reversed. If it doesn't read at all, it could prevent the PCM's power relay from working.

If that checks ok, then move to the PCM's electrical connector on the firewall & back probe the B+ feed wire to the computer there & see if it's making it that far.

If not. then there is likely a wiring or electrical connector/pin/socket problem between the B+ output side of the PCM power relay & the PCM firewall electrical connector.

Did this problem come about after an "event" like a jump start, ect????

 

I will check the diode.
Asked my boy if he did a jump start and he said yes.
So yes, the trouble started after a jump start.

 

Diode was bad, no resistance. Replaced it and it lives.
Thanks everyone for the help.

 

OK, good feedback & to hear your on the road again.

Now you may have a spare computer if the diode blew fast enough!!!!
If you don't want to re-install it to find out, most autoparts stores will bench test it at no cost.
Would be interesting to know if it's still ok, if not it may be salvageable & is worth something, so don't toss it out, if you don't want to have it reworked.

 

Yes it is a good thing i have another PCM because the truck didnt get very far. Put the other PCM in and almost 2 days now and so far so good.