No spark or fuel 1999 4.0.

[cp2295]

Got a 99 with a swapped in 4.0 with a 98 PCM. Worked fine the 7 months I've had it but I was driving today and all of a sudden it shut off. I have no spark and the fuel pump doesn't make the whirring noise when you put the truck Into the on position. I also don't have the cel flashing like it usually does when you turn to the on. I cannot connect my scanner to the truck either. All she does is crank but no start.

What would cause this is my PCM fried?

 

[martin]

check all the fuses first with a meter, don't just look at them.

 

[cp2295]

Which fuses should I be looking at exActly? I just unplugged the PCM power diode and it I got nothing to the starter at all so I know that fuse is good

 

[cp2295]

I've got 12v at the coil also. Could it be a crank sensor, ignition switch? I don't see how a crank sensor would shut off fuel and make my pcm not communicate with a scanner

 

[RonD]

Should be an EEC(PCM) Relay in the engine fuse box, that should click when key is turned on
It passes PCM power from a 30amp Maxi fuse(slow blow) in same panel
Fuel pump relay is powered by the PCM relay closing, so the two are related via that 30amp fuse and EEC relay itself.

Coil is on a separate 25amp fuse in this panel
Fuel pump power is from a 20amp fuse in this panel, but fuel pump relay has to close for this power to pass to fuel pump

Try your horn, lol, it is on the same fusible link as PCM Memory power.

CKP(crank position) sensor failure would cause no spark and no injectors but CEL would come on as normal, then stay on after cranking because of no CKP pulse

 

[adsm08]

My first instinct is that the PCM power relay has died. Swap it with the headlight relay if you have one. The horn relay should also be a viable replacement.

The PCM power diode is not a fuse, it's a diode. That's not the same as a fuse.

PCM memory power failure will not cause a no start. It will cause issues with KAM and programming, it should not cause a no start

Also check the resistance on your CAN lines at the DLC. The resistance should be between 55 and 65 ohms. If it is closer to 120 then you have lost one of the terminating resistors. Either the one in the PCM or in the instrument cluster. Loss of either one will crash the high-speed CAN and cause your issue.

 

[cp2295]

My first instinct is that the PCM power relay has died. Swap it with the headlight relay if you have one. The horn relay should also be a viable replacement.

The PCM power diode is not a fuse, it's a diode. That's not the same as a fuse.

PCM memory power failure will not cause a no start. It will cause issues with KAM and programming, it should not cause a no start

Also check the resistance on your CAN lines at the DLC. The resistance should be between 55 and 65 ohms. If it is closer to 120 then you have lost one of the terminating resistors. Either the one in the PCM or in the instrument cluster. Loss of either one will crash the high-speed CAN and cause your issue.

Is there a diagram? I'm not familiar with the can/dlc lines.. Or if you can describe which ones to probe (I'm assuming this is at the obd2 port right?) I've swapped with my blower motor since it fit and looked the same, blower motor still worked, truck still didn't start.

Also let's say it's close to 120 ohms how would I tell if it's the PCM or the cluster?

 

[adsm08]

The pins at the OBC II port (DLC or "Data Link Connector) are the second cavity on the left, top and bottom. IIRC Ford leaves the first cavity open, so it will be the first pins.

While this issue should be fairly easy to diag if I could have hands on time with the vehicle it gets harder to do over the internet. I have access to the tests for this, but the format they are written in makes them hard to just copy and paste into the forum. The board just doesn't support the formatting.

I attached a word document with the first test. I don't have time to throw the wiring info in it right now.

 

[cp2295]

So I had a short which fried the ecu. Lucky for me they had a 4.0 5speed ecu at my local junkyard! Fixed the short, cleaned up some of the fuse connections and plugged it in and it fired right up

 

[RonD]

Thanks for the update.

PCM(ECU) failure doesn't happen often