I have been having similar problems with my '99 Alero. I was able to defeat the BCM tripping the tamper mode "a.k.a. passlock issue", albiet temporarily, by doing the following:
I would experience the problem if the keyless entry system failed to unlock the doors and I manually unlocked them instead. The first time I tried to start it, after a few seconds the fuel injectors would cut off, killing the engine. After the third attempt of starting the car it would not turn over at all.
After three attempts of trying to start the car when experiencing passlock issues the BCM will tell the PCM to temporarily disable the fuel injectors for about 10 minutes or so (hence the relearn with the key in RUN position for 10 minutes).
I was able to defeat the above problems by turning the key to the RUN position, then putting the car in neutral, moving it a foot or two, then putting it back in park, followed by turning the key off pulling it out, putting it back in, and turning it on.
I figured all this out waiting for a tow truck. Then I drove the car into a dealer who provided me with the following information:
Intermittently failing passlock sensor & BCM. Checked for Codes.
Has passlock codes: P1610 & P1616 in ECM.
BCM has Data Loss code B2958 in memory.
Checked for bulletins, O.K.
Checked all BCM & Passlock DATA, All O.K. at this time.
Needs Ignition Lock Cylinder & BCM.
BCM $397 + tax
Lock Cylinder $275 + tax.
I declined those repairs as I didn't have $900 to throw at the car at that time, and figured I could get the parts cheaper elsewhere and attempt to do the work myself.
While driving it later that week, however, I went to start it after a short drive to the Post Office. As soon as I turned the key to the ACC position, the whole electrical system died. No more security lights, no more radio, no more power windows.
I have since attempted to replace the Ignition Switch ($129) which temporarily provided power for the wipers to work, but didn't enable the car to start. Since that initial connection, nothing will power up again. I also replaced the BCM (eBay salvage with 1 year warranty $44). I also replaced the Ignition Cylinder ($194 NAPA). And it still won't get any power anywhere.
Hazards won't work, headlights won't turn on, nothing.
The battery has 12.02 Volts.
I've checked all the fuses and nothing is blown.
I am getting juice to the wires which run from the battery to the ignition switch, but still no power!
Does anyone have any ideas what could be going on here?
I've already purchased the replacement parts and plugged them in, the last thing I want to do is bring it back to the dealer all torn apart, so they can charge me even more than before and get a good laugh at my expen$e.
Thanks,
'99 Alero V6 3.4L with 78k miles.