PCM wiring

[Effieman]

Anyone know where to find a PCM pinout guide?
Or what years overlap? I've found a 96 and 2000, but mine's a 98.

 

[RonD]

PCM wiring pins don't really change. 1995 and up EEC-V were all the same, the engine size and transmission type would change the number of pins/wires used, and the software inside changed.

2000 won't work, the 1998 4.0l engine will use 3 wire Cam sensor, 1999 and up use 2 wire, different signal types, there is no wiring conversion for that

And 1996 won't work either, fuel calculations are based on 30psi fuel pressure, 1998 and up used 60psi pressure

PCM also needs to match transmission type, auto or manual, and if auto, 1997 and up 4.0l Rangers used 5R55E, 1995/1996 used 4R55E

The 2000 is the closest match(assuming transmission matches), and you should be able to buy a 2 wire 4.0l synchronizer and cam sensor and then get 2 wire connector from wrecking yard to splice in to harness
The Cam sensor's one signal wire to PCM was the same, signal and ground, 3rd wire just had 12v added for hall effect type sensor
And software in PCM was different for 2 wire sensor which is why you need to use 2 wire Cam sensor

Ultimately getting 1998 PCM matched to trans would be best, refurbished they run about $150

PCM has a code number on the label that can be matched

 

[Effieman]

RonD: With all that info, maybe you could also help with another problem.
I replaced the PCM with a 'pre-programmed' one from Rock Auto. It works, until it doesn't want to start anymore. Then, I can connect the code reader to it, and it will start again...until it won't...repeat.

 

[RonD]

What codes do you get when you connect reader after the no start?
Does it connect to the computer OK?

If no code I would set a code after you do the reset and it starts again

i.e. after it's started up and idling unplug the MAF sensor, it shouldn't stall but might, no matter, plug MAF sensor back in restart it and drive it a day or so then read codes, should have a MAF sensor code in memory
If not then PCM has a problem, which you already know, lol, see if they will take it back on exchange or to reprogram.

Can't think of anything in the PCM that will automatically reset by connecting OBD Reader, or do you have to do a reset to get it to start again?


In 1998 4.0l about the only sensor that could cause a No Start is the Crank sensor, if its circuit inside the PCM was failing then no spark and no fuel injectors, PCM doesn't even know you want to start the engine until crank sensor starts to send it AC Voltage.

Other thing would be Fuel Pump Relay, if computer doesn't Ground it then no fuel at the engine.

After there is a No Start, before using OBD Reader, try 50/50 test
Spray gasoline or Quick Start(ether) into the engine and try starting
If it starts and then dies then no fuel is getting into the engine but Spark is working
If it doesn't start then No Spark
50/50

If there is no spark then computer isn't detecting engine turning over from Crank sensor AC Voltage

But I can't see either of these things being changed by hooking up OBD Reader

 

[Effieman]

It never has a code, stored or pending. The reader USUALLY will connect, but sometimes it won't on the first try.
I don't have to reset anything with the reader to get it to start again, just hook it up, let it connect, and it will start.
ONCE, I was able to turn the key completely off, then it started up again w/o hooking up the reader.
Have to try your suggestions and go from there.
Thanks.