My 2000 Astro van AWD with 230,000 miles threw a p0740 code. So I started to investigate, checked wiring and Ohms on the solenoids and all looed good. I bought a bi-directional scanner to further investigate, I figured it would be cheaper then a parts canon. While driving, I can lock up the TC with 0 slippage, also the CEL comes on as soon as I turn the key on with the van not running. Could it be a bad ECU??
Thanks for looking

My 2000 Astro van AWD with 230,000 miles threw a p0740 code. So I started to investigate, checked wiring and Ohms on the solenoids and all looed good. I bought a bi-directional scanner to further investigate, I figured it would be cheaper then a parts canon. While driving, I can lock up the TC with 0 slippage, also the CEL comes on as soon as I turn the key on with the van not running. Could it be a bad ECU??
Thanks for looking

CEL should light with key on as well as all the other bulbs. Are you saying it codes as soon as Key on? If so it'* wiring but then you shouldn't be able to command it to well.

That'* what has me stumped, I can clear the code, turn the key on without starting and it comes back. Then when reading live data while driving, the TCC never engages unless I tell it to with the bi directional scanner. Then it engages with 1 to 5 slip RPM'* on the TC. That'* why I'm thinking it could be the ECM

​​​​​​​I doubt it.

I suspect a wiring issue under the car. I'd check all wiring that approaches and connects to the outside of the transmission, including connectors and inside the connectors. I've seen a lot of Astros and Safaris have corrosion issues that cause issues like this there.

Merged duplicate threads. Post #2 and Post #5 are from the other thread.

But why can I force the TC to lock up with the code reader?

I checked the continuity on the wires from the solenoids on the valve body to the plugs going into the ECM and they all tested good, along with the ohms of the solenoids.
Getting more and more stumped. But hey, at least I had a good excuse to get a trans pan with a drain on it.

P0740 indicates a problem detected on the circuit, but not necessarily that the circuit is open or failed or whatever. I'd still go about checking for damage and corrosion on the wires and plugs.

Checked and cleaned everything, I'm leaning more and more to changing the Black Box ECU out with a 0411 one.