Odd start up issue (& P0430 code) - GS300, Mk3

[OJWM]

Hi all, 

I have an odd issue - wondering if anyone else has experienced similar... 

For context, I currently have a P0430 code (bank 2 catalyst below threshold). It's the only code and repeats reasonably quickly if cleared. It's not a surprise as I was aware the cat was on its way out... 

My issue is that on a couple of occasions recently, I've started the car and it has been *really* low on power for a couple of minutes - i.e. I can rev to. 3000-4000 and barely move.

After a couple of mins and a bit of revving, the issue disappears and the car drives totally normally for the rest of the journey, whatever gear it's in... It also doesn't do this every time it has been started recently. Both times have been cold starts. 

Has anyone experienced similar? I've spoken to a couple of Lexus specialist garages over the phone. Both thought it wouldn't have been the cat, but was more likely transmission, or torque converter. 

[OJWM]

UPDATE:

I used a different OBD reader and have discovered some more codes... Felt strangely happy about that given I've been speaking to a couple of garages who suspected a transmission issue.

Codes are:

• PO430 - Bank 2 catalyst below threshold
• PO500 - Vehicle Speed Sensor Circuit Malfunction
• C1201 - Engine Control System Malfunction or ECM / TCM Malfunction
• C1241 - Low Battery Positive Voltage

I begin to think that all codes are related and causing my startup issue. I wonder if there's a problem with my brake actuator which is related to the speed sensor problem and that is triggering the ECU to enter a fail-safe condition, which means I can rev as much as I want while the car barely moves (until the car decides there isn't a problem any more, which is eventually does)....

I do think it's unlikely that my issue is transmission related - once car sorts itself out, it shifts totally normally. Issue is also intermittent.

Has anyone experienced anything at all like this? Though I've been looking over plenty of LS460s on AutoTrader, it'd probably be a lot more sensible to fix this car (and keep some optimism that I can, for the moment at least)....

[The-Acre]

I've found in the past that it really can pay to take the car to a place that specialises in diagnostic work. We have one locally and they have code readers that cost many thousands. DIY ones are helpful but nothing beats a top notch machine matched with someone who knows how to use it, might be worth a try?