What kind of code scanner is being used to read the codes? Lots of OBDii scanners will read ECU codes only and won't tag codes from the ABS module, Body Control Module, etc.

There's a handful of ECU codes/faults that will cause traction control to fail as well, but downstream O2 sensors aren't generally one of them. At my work (Ford tech), engine control faults that will trigger ABS failure on 2000-2010ish cars basically include electronic throttle body faults, MAF and MAP sensor faults, occasionally certain transmission faults. Newer cars are more sensitive as the ABS module is pulling more information from different modules/sensors. I'd be surprised if 2000-2010ish Toyotas were any different but have no direct experience with them.

Side note, O2 extensions are useless in California and most other states with emissions tests. The ECU has to run a set of tests called "monitors" that must pass in order for the car to pass the OBDii test during the smog check. One of the tests the ECU runs is to monitor downstream O2 signals and look for a decrease in voltage during decel (should see the voltage signal drop from ~0.8v during cruise to 0v at decel as overrun fuel cut enables). If this test never passes, the O2 monitor never completes and the car won't pass smog, even if its not throwing a CEL.

But I guess they're useful if the current downstream O2 wiring isn't long enough

 

They worked to get my 2015 Expy through smog. I will still get a P013A rich to lean code for the reason you stated, though, but its intermittent enough to get through a cycle so the monitors show ready.

 

Dang, that’s the first time I’ve heard of a success story with those things. Good to know! Disregard me

 

I suspect it only works with converters that are borderline marginal. Oddly enough, I only get the lean to rich code on a single bank to boot.