Solved No CEL & no start.

[Morley]

My son has a 1999 SOHC Explorer and today he stopped the truck and shut it off and tried to restart it. It wouldn't start, just cranked over. The CEL was working at that time. Now when the key is turned on there is no CEL and it just cranks and cranks and the scan tool can't link. It has good fuel pressure, checked spark with a timing light, it is good. Checked the PCM diode, good, swapped out the PCM relay, no start still. Pulled the PCM connector and checked pin 71 to ground with they key on, no power.
I'm pretty sure that the PCM power wire goes through the large block connector mounted on the left valve cover but I can't find any pinouts for it. Anyone have the pinouts for it or know where I can get them? Also, anyone have any other ideas on the no power to the PCM?
I don't believe PATS is an issue, the light blinks slow and steady as it should.

Hate troubleshooting wiring without diagrams.

Thanks,

Ken

 

[BrooklynBay]

Welcome to this forum! Did you check the PCM fuse?

 

[imp]

My son has a 1999 SOHC Explorer and today he stopped the truck and shut it off and tried to restart it. It wouldn't start, just cranked over. The CEL was working at that time. Now when the key is turned on there is no CEL and it just cranks and cranks and the scan tool can't link. It has good fuel pressure, checked spark with a timing light, it is good. Checked the PCM diode, good, swapped out the PCM relay, no start still. Pulled the PCM connector and checked pin 71 to ground with they key on, no power.
I'm pretty sure that the PCM power wire goes through the large block connector mounted on the left valve cover but I can't find any pinouts for it. Anyone have the pinouts for it or know where I can get them? Also, anyone have any other ideas on the no power to the PCM?
I don't believe PATS is an issue, the light blinks slow and steady as it should.

Hate troubleshooting wiring without diagrams.

Thanks,

Ken

@Morley
I have only '96 wiring diagrams, which engine have you? I can scan pinouts tomorrow of '96, if you feel that will help. BEST diagrams are Ford, from Helm, Inc. imp

 

[Morley]

@Morley
I have only '96 wiring diagrams, which engine have you? I can scan pinouts tomorrow of '96, if you feel that will help. BEST diagrams are Ford, from Helm, Inc. imp

It has the 4.0 SOHC. The pinouts for 96 should be the same. I don't have a manual for the vehicle and really the only thing I would need a manual for are the wiring diagrams which I can find on line, just not the connector pinouts.

Thanks

 

[Morley]

Welcome to this forum! Did you check the PCM fuse?

First thing, then the relay swap. I do believe my next step is tracing power from the fuse box towards the PCM., just need the pinouts for that large square connector. Failing that I guess I can remove the fuse box and trace the wires from the relay to the connector. Either a wire is broken or the power isn't getting to the fuse box to actuate the relay

 

[BrooklynBay]

This once happened to my 1988 van. I had a blown fusible link. I think that the high current fuse box on the later models replaced the fusible links which were used on the older models.

 

[Morley]

First thing, then the relay swap. I do believe my next step is tracing power from the fuse box towards the PCM., just need the pinouts for that large square connector. Failing that I guess I can remove the fuse box and trace the wires from the relay to the connector. Either a wire is broken or the power isn't getting to the fuse box to actuate the relay

Ok. I have found that the PCM power diode doesn't have power going to it. I was able to jump out the power side of the relay and now the PCM has power (CEL comes on) and the scanner connects to the PCM and says no fault codes but the engine still won't start (just cranks). Anyone happen to know where the diode gets power from?? I pulled the fuse box apart and there are 2 power wires going to the diode, those wires come up from the main harness they are red with yellow stripes.
Anyone got a clue where they go? Ignition switch? I'm thinking that whatever is preventing power from getting there is also stopping the PCM from firing the injectors

 

[Morley]

This once happened to my 1988 van. I had a blown fusible link. I think that the high current fuse box on the later models replaced the fusible links which were used on the older models.

Yeah, the fuseable links were replaced with those huge fuses in the box. Some places the still call them fuse links.

 

[Turdle]

Do you have power to the cigar lighter?

You might try this, there could be a bad connection at either-


2nd gen issues? Try this first!

Also, an idea on which fuse is which might help. PCM has several protect fuses it seems



This one should be close to yours

Fuse and relay locations--2nd generation power distribution box Layout-

#6 mini fuse in the power box under the hood

#19 25a in the interior fuse panel

#5 in the interior panel is the data link connector fuse

 

[Morley]

Do you have power to the cigar lighter?

You might try this, there could be a bad connection at either-


2nd gen issues? Try this first!

Also, an idea on which fuse is which might help. PCM has several protect fuses it seems



This one should be close to yours

Fuse and relay locations--2nd generation power distribution box Layout-

#6 mini fuse in the power box under the hood

#19 25a in the interior fuse panel

#5 in the interior panel is the data link connector fuse

Lighter has power. Checked those fuses yesterday and again with a meter, all good. Just replaced the ignition switch, no change.
Do you happen to know where the PCM relay diode gets power from? I THOUGHT Auto Zone had the schematics for the Explorer but they don't.
Also disconnected the PCM connector yesterday looking for power on pin 71, Didn't see anything unusual. I am certain my problem is that I don't have power going to the diode...just don't know where it is supplied from. It goes without saying that I don't have any RPM signal when cranking too since the PCM is not powered

 

[Morley]

Fixed.
I was removing the 25A fuse, supposed to be #19 (couldn't open the door all the way to see it) Seems someone put a 25A in #23 which should be 15A. #19 had apparently fallen out and #19 supplies power to the diode. I was going to check for power at 19 when I discovered that #19 was now empty. This thread How to: - Ford Explorer PCM Power Procedure tells where power comes from and where it goes to.
thanks for all the help

 

[BrooklynBay]

Thanks for the update. Your thread is now marked solved.