2002 Ford Escape • 3.0L 6 cylinder 4WD Automatic • 230,000 miles

I am having a presistant engine line on issue. I have taken the car to AutoZone and got a P3501. The printout indicates possible defective ignition coil #1, connector, wirings (12v and the server) or PCM. I have swapped coil and spark plug with cylinder #6 and continue to get the P3501 error.
I took the vehicle to the dealer #1 who confirmed PCM and wiring are good and it must be the coil. I indicated that I have already swapped the coil and spark plug. They still said it must coil #1. They reset the codes. I purchased and new coil #1 from dealer and replaced it. I drove for a couple of days and then got the engine light and same code again!
I took the vehicle to dealer #2 who confirmed all is Ok (Wiring PCM and Coil). They reset the codes. Drove for a couple of days and got the engine light on again!
The engine light is usually triggered when starting the vehicle and it is very cold outside
What are some other possibilities? What would you recommend doing next?
February 3, 2014.

Just an idea. Is there any dirt or grease down in the #1 hole the plug goes into? The plug will ground at the threads. Not usually a problem but easy to check. Also this misfire could be an injector on number one also. Make sure its plugged in properly. These plugs like t get brittle and the tabs break off. If that's ok swap the injector as you did the coil if youre up to it. Lastly you may have a non visible crack in the plastic intake at cyl 1. That would explain the more prevalent code when cold. As the intake heats up it expands closing up the vac leak

Thank you for the reply. The coil area is clean. So I will check the injectors and intake manifold next. Why would a fuel injector issue resulght in s P3501 code? Thought this was limited to electrical issues. Thanks, Jay

Feb 6, 2014.
I cnt actually find a p3501 code but if you have a misfire code it jut means the cylinder is dead not necessarily just the spark. Loss of air, comprssion, spark, or fuel will cause a misfire code

The code is actually P0351. Sorry. Could this also be an oxygen sensor or not?

Feb 7, 2014.
Ok. Now weve got something. Theres a service bulletin by ford that says this code can be set by damaged wire or connection at the PCM for this coil pack. Check the light green wire with the white stripe at the PCM plug for female terminal damage or insulation damage. The pc is in the middle of the firewall in the engine compartment I a little recess