I am not sure if this will help or not...
I came across this suggestion ... Unscrew the ECU and turn it 90° and
retighten it. It could be something to do with the way the connector sits
in its slot.

On Sun, Apr 23, 2023 at 8:47 AM Alistair Bell <ragnarhairybreeks@icloud.com>
wrote:

> First I have to say again, this last week after my work on the ecu last
> weekend…the van ran sweetly. I mean I couldn’t stop talking about it to
> anyone that would listen. I was over the moon.
>
> Yesterday I thought I’d look at the harness connection to the ecu and
> especially the ground wire from it to body. Long story short… couldn’t see
> any issues. Decided at this time not to add anither ground.
>
> So I reseated the connector and… van cranks no start.
>
> Reseated again , starts and runs but high idle ( I’d say 1500) but Tach
> bouncing around 3500.
>
> Was texting all this to David B. Both of us puzzled. Of course we
> suspected solder joint failure on a pin or two in the ecu where the
> connector attaches to board.
>
> Out comes the ecu and more examination of the board. I didn’t take the
> mother/daughter arrangement apart. I was afraid if doing damage to the
> ribbon connector etc.
>
> Found another iffy solder joint on board , not at the connector. But
> reflowed it anyway.
>
> I didn’t reflow the connector pins to board. My skills fall short for such
> small connections as those.
>
> Reconnected ecu…. No go.  Reconnected again…it goes, nicely, sweet.
>
> Btw I did clean the connections and sprayed de oxit.
>
> Good friend Greg, the replacement foil guy, has a d code Ecu that he has
> gone over, he’s giving it to me today and we will see what happens.
>
> Oh and when the van is running right, I can move the ecu around and twist
> and tug and no change in running.
>
> It’s annoying but I think it’s gonna work out ok. If the symptoms persist
> after the ecu swap then I’ll go back into the harness connector and examine
> much more closely.
>
> But right now I do suspect the ecu .
>
> Alistair