No codes, "Service Engine Soon" light stays on steady, no flashing

Thank you, Joe! I will test in the morning and report back.

Joe, I don't see my previous reply, so I'll try again. There is no 12v signal on Terminal B of the OBDI port. No power to anything in that port. That is with the key in the "on" position. If nothing is getting to the OBDI connector, does that mean the ECM is defective (P/N 16147060)?
Thanks,
Rich

Joe, I can confirm the fuse in the fuse box is good (I checked everyone of them :-), but I did not know about the other one. It looks like a relay. Is that located on the firewall, passenger side? I'll check there.

Okay, I just went out with a flash light and removed the cover and found two grounds, fuel pump relays and an inline small fuse. I checked the fuse for continuity and it was good. Put it all back. Is that inline fuse the one to check?

I should state - the truck runs good. I can drive it. But it seems like it's starting out in 2nd gear and maybe shifts to 3rd, but will not shift into 4th, nor lock up the converter. I turn about 3,000 RPMs at 50 MPH. The "service engine soon" light is on and that's what I'm trying to understand, why it won't flash codes.

Joe, I previously checked the Transmission Control Module and it's connector. Seems okay. I didn't check for 12v at the firewall locations. I'll do that tomorrow morning. Tonight, I ordered a remanufactured ECM (BSE's ECC-7060). Hope I can get it tomorrow. I'll report back.

Hi, Joe. Sad news. (I hope you'll continue to help.) I checked power at the connections on the firewall (fuel pump and fuel pump relay) - all had 12v power. I double checked power to Terminal B in the OBDI port. There is no power when the key is on. I received and installed a new ECM (after disconnecting both positive and negative terminals on the battery and touching them together). All the wires and connections looked good (truck overall is very clean with zero rust, just dust). I used di-electric grease when connecting the new ECM. After install, I still had no power to Terminal B. I removed the OBDI port, found the wire to Terminal B is white with black stripe. I found the same white/black wire in the ECM connector and poked the sharp point of my 12V test light and still had no 12v power (with the key on). I'm stumped and very disappointed. Any suggestions?
Again, thank you very much for your assistance.
Rich

Just saw your reply. I’ll check the fusible link tomorrow. I’m wondering if the truck would run if one of the fusible links failed. Aren’t they supposed to reset themselves - never have like fusible links. The truck runs fine. The two issues are: (1) the “service engine soon” light is on and (2) the transmission is in limp mode. Regardless, I will check the fuse and report back.
Thank you!
Rich

Joe, I have to admit I was in bed when I saw your last reply about the fusible links. I opened the drawing this morning and see that it shows the connections under the plastic cap on the passenger-side of the firewall. I previously checked all those and everyone had 12 volt power. That is the location of the small in-line fuse that I also checked (it was good). Does the ECM get its power from those connections? If so, I'm guessing that would mean the ECM is getting power. Yet two different ECM's are not providing power to Terminal B on the OBDI port. This is both interesting and frustrating at the same time. What can it be? Thank you again! Richard

A friend and I have checked several things today:

1. All the fusible links are good
2. There is a connector to the right of the junction block coming out of a large wiring loom that has a white/black wire (same as Terminal B in OBDI test port). There was no 12v power to either side of that connector.
3. We checked all the wires going into the ECM (the right side plug) and found only four have 12v power - purple/white, tan/black, solid green and yellow/black
4. We checked the white/black wire coming out of the new ECM (left side plug) and found there is no 12v power present.
What else can we do?

Rich

I crawled underneath the truck to see if I could find any broken wires, wires with abrasions of plugs disconnected. The only thing I found were two plugs beside the transmission that were not plugged in - a four prong and a 2 prong. But could not see the other side of the plug nor where they might plug into anywhere.

Hi, Joe. I was sure to report the white/black wire (as having no 12 volt power). If I am correct in assuming the right side plug going into the ECM is the input side, I checked all the wires:
Green - ground
Black/white - ground
Solid black - power
white - nothing (neither ground nor 12v power)
purple - nothing
blue - nothing

these were all tested with the key "on"

I can report there is no 12volt power to any terminal in the OBDI port. I made sure my test light was working by checking fuses and getting the light to illuminate with 12v power. Again, this is all with the key "on".

I tested the leads within the left side plug of the ECM and found power at the following:
yellow/black
solid green
tan/black
purple/white

Note: the lower right two terminals on that same plug are grounds (orange and pink wires).

I hope you have some idea of what problem I have cause I'm at a loss.
Thanks for your help.

Rich