Ok, I am out.

 

The only common point of your symptoms is the fuse box or, the main ground on the trans.
That youtube is not good for diagnosing or repairing it is good for procedure.

If the battery is good and the connection to the fuse box is good it is probably something inside the box.

Maybe, grounding the TCM actually bypasses the main ground? The ground point on the trans connects to the driver side wheel well. Maybe, you are just replacing that connection. The body is ground not the engine.

Drilling a hole in the TCM is bad, adding a place to short the TCM is bad; that is what the hood over the TCM and ECM is for.

 

Just a follow up for anyone who might come across this thread....

The security light eventually came back on and stayed on instead of going on and off intermittently. . I checked some of the grounds without luck. The light stayed on, gages did not work, engine misfired. The check engine light threw a single code having to do with no communications. I then replaced the ecm/pcm module with a reflashed unit from ares technology and the security light immediately went out, guages back to normal, ect. Its been about three weeks now with no problem. I am wondering whether the problem I experienced about a year ago was actually a different issue that was corrected by adding the ground. At any rate I am keeping the ground on the TCM. If something goes wrong again I will update here.

Note that it is necessaryr to reprogram the keys to the get the car to start after replacing the ecm. There are quite a few videos showing how to do this reprogramming.

Also, as part of the trouble shooting before replacing the ecm, I disconnected the battery and reconnected it. That did not fix the problem. I then disconnected the battery and replaced the ecm.

 

Good thanks for your follow up and letting us know your problem is resolved!

 

Also want to mention that when the ecm is replaced a code p0315 (crankshaft position system variation not learned) will appear. Rather than pay a dealership $300 or more to do the relearn procedure I purchased a foxwell 510 elite for GM cars scan tool (abaout $150) and was easily able to do it myself. The relearn procedure is in the special functions section of the tool. The necessary steps are stated on the tool screen.

 

Why would a dealership charge 2-3 hours for a 15 minute job? It is listed at 1 hour flat rate.

 

Why would a dealership charge 1 hour of labor for a 15 (more like 5 minute) job? But your right, I was mistaken. It would cost whatever an hour's of labor cost at the dealership ($200?).

 

1 hour is a typical minimum charge.

 

I think the going rate at a dealership is $150. Other shops have computers that can do it, they are generally cheaper.
Flt rate includes get the car in and out of the shop and a couple of cigarettes an hour and standing in line at the tool shack and time to read the procedure in the shop manual
For warranty work they charge themselves. .8 hours.