I have a 96 ranger 4x4 with a 3.0, it turns over fine but when I turn the key on the pcm relay does not energize, I can spray either and it will pop, I jumped the fuel pump relay and the pump runs, there is no check engine light with the key on and I have hooked up a scan tool and it says communication error, I'm thinking pcm but any help would be appreciated

 

Yes, PCM relay powers up the PCM(computer) and fuel injectors and Fuel Pump Relay(not the pump)

PCM relay has a full time ground so is activated by Key on 12v from ignition switch under steering column, via fuse 19 in the cab fuse box

Ford used two style of relays, Mini and Micro
Mini seen here: https://www.gtsparkplugs.com/images/...iring-840x.jpg

Micro seen here: https://www.gtsparkplugs.com/images/...lay-wiring.jpg

What their slots do the the same on both
87A may or may not be present, its not needed in most relay applications

85 and 86 activate the relay, there is no polarity(unless relay has a diode inside), so id one is a ground and the other 12volt then relay actives
When activated the relay connects slots 30 and 87 together, in this case, powering up the PCM and other components

So with relay out test slots 85 and 86, should see 12volt or -12v if key is on
If not then see whats missing, the ground or the 12v
Put probe in 85 then touch other probe to battery negative if you see 12v then slot 85 is key on 12v, if no volt then move probe to battery positive, if you see 12v then 85 is a good ground
Do same test on slot 86 to see if you are missing the 12volts, assuming 85 was a good ground

If no 12v at PCM 85 or 86 then check fuse 19 in the cab fuse box, 25amp fuse, it also powers the Coil Pack

Also check PCM Diode its in the Engine fuse box and has this symbol on it " -->|--- " an arrow pointing at a straight line, pull it out and check for corrosion, you can jumper its two slots together to see if you now get 12v at 85 or 86
The diode prevents voltage spikes in this circuit so is needed for long therm operation but fine to bypass for testing

If you have 12v between 85 and 86 but relay doesn't work then relay is bad

 

Thanks for the info, this is a truck I just bought and wasn't running, I had checked all the fuses with a dvm but upon further inspection fuse 19 was missing, put one in and it started right up. Thanks again

 

Thanks for posting "the fix",

Many don't so we never find out what worked