[Architect]

So to be clear:

• You replaced the engine and kept the PCM and the complete wiring.
• When you turn the key to Run:
  • The THEFT light keeps on blinking every 2 seconds.
  • You do not hear the fuel pump in the back engage for a few seconds.
  • The OBD adapter does not connect to the PCM (note the ignition must be in Run for that).

Since the very first time the engine actually did turn over, the PCM must have worked and have recognized the key. Perhaps you can carefully check the ground strap of the PCM.

You could also check fuse 23 (Air Bag Module and PATS Transceiver) underneath the dash.

As far as I know, there is no such thing as a "PATS lockout" (a key is recognized or it is not).

Note that the locking and unlocking of the doors (among other things) is done by the GEM (General Electronic Module) underneath the dash. It does not prove the PCM is working.

 

[Architect]

Fuel pump. Yes, hear it run for just an instant, but not always. I would say funny behaviour right now. ( unclear though, makes a moan or groan, then stops. I am familiar with the sound it made when car was working all find before the engine change... and could be suspect. A fuel pressure check might be in order. )

This seems OK. It indeed moans and groans for 2 seconds. This also shows that the PATS is recognizing your key. If it doesn't, the PCM will refuse to start the engine, and will not bother powering the fuel pump either.

I went into the 2000 Taurus service manual on CD, and read some more and printed schematics and pin outs and location drawings for a few connectors related to the Starter System relay wiring. The part of the circuit that provides ground to the starter relay in the Fuse Box beside the battery in the engine compartment. It shows a pink wire, leading from pin 86 (from memory) of the starter relay, through another connector on the driver's side fender of the car, then over to the PCM connector, pin 44 i think from memory. It says to check the resistance of this path, and if greater than five (5) ohms ... "fix the circuit".

Yes, that is correct. The schematic (from paper version of the 2000 Wiring Diagrams):

The PCM will only start the engine if the transmission is in P or N. The Transmission Range Sensor (TRS, a.k.a. Neutral Safety Switch or NSS) only powers the Starter Relay (in the schematic called K22, but it is relay 23 in the engine compartment) when the ignition is in Start and the Transmission in P or N. Relay 37 under the dash should of course be fine.
This is the wiring of the TRS:

Through pin 6 of its connector it also informs the PCM (pin 50) that the transmission is in P or N. Without it, the PCM will not even try to pull the other side of the Starter Relay to the ground.

So, you could:

• Pull the 12 pin connector from the TRS, push it back in and try to start the engine again.
• Check the Starter Relay (#23 in the engine compartment) by interchanging it with the one next to it (#24: Low Speed Fan Relay) and try again.
• Pull out the Starter Relay alltogether.
• Connect the terminal where pin 30 of the relay would go to the battery positive. The starter should run immediately, even without the key in the ignition. Beware that there is no safety at this level and the car will happily run you over if the transmission is not in P or N.
• Put a 12V test light between the terminal where pin 85 of the relay would go and the ground (or battery negative).
  • When you try to start the engine, the test light should light up indicating the TRS agrees that the transmission is in P or N and powers the relay.
• Put the 12V test light between the battery positive and the terminal where pin 86 of the relay would go.
  • When you try to start the engine, the PCM should pull pin 86 to the ground and it should light up again, indicating the PCM also understands the transmission is in P or N and that a valid key was recognized.

 

[Architect]

Now that I think about it again: it is very strange the OBD monitor does not connect. So one question: when you hear the fuel pump "moan and groan" in the back for 2 seconds, the THEFT light in the instrument panel is out, right? Just to rule out that my statement "fuel pump runs, so key is recognized" is in fact wrong and that it indeed could be the PCM.

 

[Architect]

I assumed that the PCM is either working, or it is not. But that is not true. It uses way too much power and will drain the battery if it would be fully on all the time. See this schematic:

The PCM gets (pin 55) its Keep Alive power. It will probably keep the PCM in a kind of sleep mode (doing things like blinking the THEFT light). It only really powers on if it receives power on pin 71. So you also need to check fuse #2 in the engine compartment, fuse #25 underneath the dash and relay #31 in the engine compartment (this is what K163 is), for example by interchanging it with relay #33 next to it (A/C clutch).

 

[Architect]

The fact you can't communicate and pull codes (you need the key to be fully on but it should still work) means it may have died on you.

Agree. This really sounds like a bad PCM. There is definitely power on the PCM (pin 71 of the PCM and pin 5 of the relay) and it even draws 2 A. Yet the OBDII monitor does not connect. And the key is not recognized (THEFT light keeps blinking).

I'd say that checking of the TRS or any of the fuses is not needed. The PCM is dead.

 

[Architect]

DPFE sensor is part of the control system for EGR - Exhaust Gas Recirculation system.
...
It must get hot back there / above rear exhaust manifold.

Perhaps it was loose at one time and fell onto the EGR pipe.

This is what happens if an Oxygen Sensor connector falls onto the EGR pipe:

Even the hard ABS plastic melts.