Pcm location/diagram

[RonD]

EEC Rely powers the PCM(EEC) when key is turned on, it also powers the TFI module and fuel injectors, and you have tested those and they have power, so Relay is closing

On the PCM pins 37 and 57 get power from the EEC Relay, these power up the PCM

Pin 1 should have 12volts all the time, that is the KAM(keep alive memory) power, like radio pre-set and clock memory power, small voltage draw that allows PCM to hold Long Term Fuel trims, IAC settings and any codes in memory.
KAM power can't run the PCM, just hold memory.

Pin 17 is the Ground for the CEL, the CEL bulb gets 12volts when key is on, the PCM grounds the bulb(pin 17) to turn it on

 

[90rangerext29]

Ok, installed new eec computer and nothing. Now comes a stupid question I have assumed the red ovals in this photo are the grounds for the eec, so are they?

 

[RonD]

Posted the diagram from here: http://www.auto-diagnostics.info/ford_eec_iv

Pull off connector and check each ground wire

Ford changed ground points and wire colors sometimes every 6 months, sometimes they were the same for years, so without the 1990 Ranger EVTM book not sure any one can answer your question

 

[90rangerext29]

Ok, I guess I will Hunt and trace it down

 

[FirstGenRanger]

Here's a pdf file with the ecu pinouts for the 2.9

 

[90rangerext29]

Success! Found out the grounds in the pictures are not for the eec. The grounds go directly to the battery where it was disconnected(had slipped out of a wirenut) reconnected, got check engine light and a few cranks later it was idling. Thanks for all your help RonD and FirstGenRanger