Help: Power at OB port but will not connect.

[ragtopz28]

Please bear with the newb here...
I am trying to load a new start-up tune. The port has power, all batteries charged, etc. When I go to write it appears to be "looking" for about 2 seconds the says "failed" and Controller Unlocker:Timed Out.
Is it possible that the computer bricked or lost the "GM tune" due to being with out power for 13 months?
I have checked grounds, looked for bent/corroded pins.
I did check my interface in two of my other vehicles and was able to connect and scan. So not my interface.
Any suggestions?
Thank you in advance.
Signed ready to start this new engine!

[blindsquirrel]

What kind of GM vehicle? Looking up wiring diagrams/pinouts/other diagnostic help for you has to start with year, make, model that most closely matches the parts you are using (harness, operating system, etc.).

[ragtopz28]

What kind of GM vehicle? Looking up wiring diagrams/pinouts/other diagnostic help for you has to start with year, make, model that most closely matches the parts you are using (harness, operating system, etc.).

My bad...it is a 1998 Pontiac TransAm Stock '98 computer working with no issues until powered back up.
Thank you,

[blindsquirrel]

screenshot.14-12-2021 18.41.28.png screenshot.14-12-2021 18.39.07.png

[blindsquirrel]

Check for signs of rodents. Do you get a 'check engine' light at key-on?

[blindsquirrel]

screenshot.14-12-2021 18.50.25.png

Hey, that's super helpful! Thanks GM!

[ragtopz28]

screenshot.14-12-2021 18.50.25.png

Hey, that's super helpful! Thanks GM!

Thank you. Those first two were very helpful. This one....

[blindsquirrel]

If you have no check engine light, and engine work has been done recently, you probably have a missing ground. You can test this with a temporary jumper wire from the PCM case to a known good ground. If you then get a working CEL and the relays click etc., go find the ground eyelet you left off the engine somewhere.

[ragtopz28]

If you have no check engine light, and engine work has been done recently, you probably have a missing ground. You can test this with a temporary jumper wire from the PCM case to a known good ground. If you then get a working CEL and the relays click etc., go find the ground eyelet you left off the engine somewhere.

Your timing is amazing. I just checked, and no check engine light comes on when key forward. I have a AEM? read all gauge that plugs into the OB port and it won't read either. I'll check grounds again.
Thinking that the computer somehow lost the GM tune. I'm gonna call a buddy that works at a GM dealer and see it they can install the "GM tune" to my vin. number. Make sense? Maybe they can find the ground issue...

[blindsquirrel]

The PCM 'losing the tune' from having the battery disconnected would be like your computer hard drive losing all your files by unplugging the PSU from the wall. Just doesn't happen, it's not volatile data like RAM.

If the PCM is missing a ground and not powering up when the IGN is on then nobody will be able to write a factory calibration to it using any kind of flash tool.

Try the jumper from PCM case to ground thing, it will rule a lot of things either in or out very very quickly.

[ragtopz28]

The PCM 'losing the tune' from having the battery disconnected would be like your computer hard drive losing all your files by unplugging the PSU from the wall. Just doesn't happen, it's not volatile data like RAM.

If the PCM is missing a ground and not powering up when the IGN is on then nobody will be able to write a factory calibration to it using any kind of flash tool.

Try the jumper from PCM case to ground thing, it will rule a lot of things either in or out very very quickly.

I'm not the best when it comes to wiring. I have a couple of "wiring guru" friends but they are non-responsive atm. I agree with your theory of it not 'losing the tune' but was told otherwise by a 30+ year GM tech. I'll look for grounds again. Where am I looking? All of the "fat" grounds and power wires are hooked back up exactly like I found them (battery relocation and ground kit). Could there be some little wire in the harness that goes to the back of the head or something I'm missing? I was almost positive that I got them all....

[blindsquirrel]

I don't really see any sense checking all the grounds until you verify that it's not powering up because of a missing ground. Jumper wire from PCM to ground will bypass any ground point that might have been left loose at the engine.

If the jumper makes no difference then you can safely move on to other things. Check fuses and any inline connectors between fuse/relay box and firewall.

[ragtopz28]

I don't really see any sense checking all the grounds until you verify that it's not powering up because of a missing ground. Jumper wire from PCM to ground will bypass any ground point that might have been left loose at the engine.

If the jumper makes no difference then you can safely move on to other things. Check fuses and any inline connectors between fuse/relay box and firewall.

Again pardon my 'electronical' abilities. The OB port has power. I'm not getting the jumper wire from PCM... Like, just a wire connected to good chassis ground and to the PCM where? I did check the cig fuse and it was good (why OB has power).
Thanks for the help!

[blindsquirrel]

The outer metal case of the PCM, any part of it that's metal is electrically connected inside to the pins that get grounded through the harness, so grounding the case directly bypasses all the grounds it'd normally get.

Turn the key to RUN, then take a wire, any old wire, stripped bare on each end, touch one end to the PCM case and one end to something that's a good ground - alternator bracket, front strut mounting nut/stud, battery negative, whatever. If the jumper wire does indeed supply a ground that's missing you will hear relays click and the fuel pump run and fuel squirting through the rails when the PCM powers up. If the ground wire does nothing, you have some other problem and can stop thinking about missing grounds, and you didn't have to crawl under the car or look in the manual for ground points or anything.

[ragtopz28]

The outer metal case of the PCM, any part of it that's metal is electrically connected inside to the pins that get grounded through the harness, so grounding the case directly bypasses all the grounds it'd normally get.

Turn the key to RUN, then take a wire, any old wire, stripped bare on each end, touch one end to the PCM case and one end to something that's a good ground - alternator bracket, front strut mounting nut/stud, battery negative, whatever. If the jumper wire does indeed supply a ground that's missing you will hear relays click and the fuel pump run and fuel squirting through the rails when the PCM powers up. If the ground wire does nothing, you have some other problem and can stop thinking about missing grounds, and you didn't have to crawl under the car or look in the manual for ground points or anything.

Hallelujah!! You are the man! Jumper wire did exactly what you said sir. I found the bad ground...it was on the driver head. I must have ripped the wire out of the connector when I was fighting the MAP and hold down bracket. Put on a new one, turned the key, and it "accidentally" fired up and I haven't even put the new tune in! I just wanted to thank you again. Sometime ya just gotta walk away...