VS Memcal problem?

[injectedV8]

I've been trying to chase down a problem with my VS V8 Series II Auto Ute for a few weeks now and I've concluded that its possibly a memcal problem. Done a bit of a search which has gotten me this far, but now I'm down to the memcal. Need some input from the memcal experts here.

I bought this car late last year, and it drives and starts fine except that as soon as it hits about 65km/h and shifts to 4th gear, the torque converter lockup activates. I've read that this is supposed to activate at about 80km/h. I've checked this with an LED connected to the TCC signal and it lights up whenever its activated. When its locked up, applying more throttle won't unlock it until it kicks down back to 3rd. Makes the car a dog a drive in 70km/h zones - I shift back to '3' to avoid sitting at 1300rpm at 70km/h.

Changed the ATF and filter, no change.

Disconnected the TCC signal and it no longer locks up, so the torque converter mechanically seems OK - drives whole lot better too since it doesn't bog down when cruising in traffic at 70km/h. ECU throws a code as expected when TCC solenoid disconnected. (No code if I put a resistor in its place to fool the ECU).

Looked up the services manuals, and it mentions transmission 'hot mode'. I checked the transmission fluid temperature sensor and it appears to read the correct voltage as it warms up according to the service manual, so ATF fluid sensor appears OK. The Auto box does behave likes its in overheat mode however.

Checked ECU codes, and I get no codes other than 12 (when TCC solenoid connected as normal). Thought I'd use a scan tool, but none of them can scan the ECU or the Auto computer. I used a Carman scan tool as well as the Holden Tech 2 - can't get much better than that. I can scan the BCM OK, so the diagnostic plug wiring is OK. Even buzzed it out with a multimeter back to the PCM just to make sure.

OK, so at this point I figure the PCM is faulty, so I pickup another at pick'n'payless, swap in my memcal, but it still does the same thing.

Thinking about getting a re-tuned memcal anyway, but thought I'd post just to ask if a bad memcal can cause these issues, both the TCC lockup problem and preventing the scan tools from working. My memcal is labelled with CKUN, with a 16176424 ECU. Sticker appears to be un-touched.

I suspect the shift patterns are messed up too, because I'm always catching out the gearbox accelerating out of corners where it needs to kick down sometimes from 4th, to 3rd to 2nd, because its reluctant to pick lower gears. If I accelerate from a standstill with lots of throttle, it goes through the gears OK, but 3rd to 4th is always shifted very short.

Keen to get this fixed because I really want to enjoy the effortless torque of the 5L V8, but with the obsessive TCC lockup and messed up shift patterns, its nothing but a slug because its always in too tall a gear.