In my original post about a week ago I had asked for help because I had pulled my PCM (aka ECU or ECM or engine computer) with the battery connnected and couldnt start the truck after I reconnected it (also with the battery connected). I thought I had destroyed the PCM by keeping the battery connected when disconnecting / reconnecting.

Thanks to all who advised. Timbersteel told me to look for bent pins and I reported no bent pins, but in fact there was one bent pin. There is a reason for why I didnt think it was bent but thats irrelevant.

Here are the important observations to help future members searching on this topic.
1. After I straightened the pin the truck started right away. So removing the PCM with battery connected does not destroy the PCM. Subford noted this in my original post.

2. My original reason for disconnecting the PCM was to clean the connector in an attempt to get rid of Oxygen Sensor codes I was getting even after changing all the O2 sensors. For the record I was getting P0141, P0155, P0133, P0135, P0174, P0171, P1131, P1132. Even before I started getting Oxygen sensor codes I had P0401 (EGR Flow Insufficient) which I haven't been able to fix for more than two years. When I got the truck running after straightening the pin, the O2 sensor codes started coming back almost immediately. I read in another thread that others had fixed the problem by replacing the PCM, so I went ahead and did that, and BINGO, the Oxygen Sensor codes seem to be gone (at least for the last two days). Will report back if they do come back.

3. However, the EGR Flow insufficient code P0401 came back so I will be chasing that some more this weekend. Any advice about P0401 will be much appreciated.

Truck is a '96 F150, 5.0L, Auto, 124K miles.

 

Thanks for the follow up.

I blame most of my frustration with bad vision, cheap dirty glasses, cats jumping and scattering tools as bad as other people borrowing stuff.

Plus it hard to really care sometimes.

Those pins are tiny and hard to see.
I cleaned mine with delicate computer type stuff NOT electric motor grease cleaner and then used some di electric grease.

Glad it wasn't a hard to find 400$ fix.

There's a bunch of stuff re: egr, egr position sensor and making a plate to restrict the volume of egr gasses thru the egr valve.

Not sure what that was all about, maybe rough idle and may have nothing to do with your codes.
..just a thought.