Well, I have a 1997 F150 with a 4.2L V6 with a 5-speed manual, and it recently bombed at 80k because of the gasket problem. I paid over $10,000 for this truck in mid-2001 when it only had 35,000 miles on it, and I have loved it until the engine went in it about a month ago. I decided because of the money I had invested in this truck, the best decision was just to replace the engine.

I was able to obtain a complete brand new generation 2001 model 4.2L engine with wiring harness, and I installed it into my 1997 F150 this weekend. The swap went very smoothly, the motor mounts bolted up exactly along with the transmission input shaft and bellhousing. The wiring harness even mated to my PCM perfectly, and all of my serpentine belt components bolted on to the new engine just fine.

Note: The 2001-04 "new generation" 4.2L is quite different than the 1997-00 "old generation" 4.2L. The intakes are the most noticable difference. But there are also electrical differences, the vacuum ports are totally different, and the throttle cables are different.

When the swap was complete, I encountered my first major problem... The vehicle will turn over, but it will not start-up. I suspect that this may be due in part to one small electrical connection coming off the main wiring harness that did not mate up. This is the ONLY other electrical connection that mates directly to the PCM other than the main big square headed wiring harness. The connection is located right behind where the main engine wiring harness plugs into the PCU. The one on my 1997 F150 is round and 4 male pins inside it with 4 wires going to it, but this connection on my new 2001 engine wiring harness is square and has 5 active female terminals with 5 wires coming out of it.

I have examined the wires in these harnesses very carefully and 3 of the wires on each harness have an identical color scheme. The 1 different colored wire on my 1997 terminal is gray/blue stripe, and the other 2 wires on my 2001 terminal is all gray and gray with a yellow strip.

I have checked with the local Ford dealer's parts department and they have no clue what these wiring harness operates and they do not have an adapter to mates these two harnesses together. I suspect that the engine is either not getting fuel or the spark plugs are not firing. Either way, both problems are electrical.

Does anyone know what this part of the wiring harness operates on the engine and if it must be plugged up in order to start-up?

 

I would start with getting a 2001 PCM. Who know what all changed. Wire counts, wire colors may be the same, but what they control, or what information is passed could be, and chances are, probably not exactly the same between '97 and '01.

 

Getting a harness and PCM from a 2001 will be a start. But as a caution, there is a dash mounted security system that requires "chipped" keys in the 2001. This may be bypassed somehow, but you'll need detailed wiring schematics to get through it.