With GST

Start engine and warm it up to the normal operating temperature.
Turn ignition switch OFF and wait at least 10 seconds.
Start engine and keep the engine speed between 3,500 and 4,000 RPM for at least 1 minute under no load.
Let engine idle for 1 minute.
Set voltmeters probes between ECM terminals 35 [heated oxygen sensor 1 bank 1 signal], 16 [heated oxygen sensor 1 bank 2 signal] and engine ground, and ECM terminals 74 [heated oxygen sensor 2 bank 1 signal], 55 [heated oxygen sensor 2 bank 2 signal] and engine ground.
Keep engine speed at 2,000 RPM constant under no load.
Make sure that the voltage switching frequency (high & low) between ECM terminals 74 and engine ground, or 55 and engine ground is very less than that of ECM terminals 35 and engine ground, or 16 and engine ground.
Switching frequency ratio = A/B

A: Heated oxygen sensor 2 voltage switching frequency

B: Heated oxygen sensor 1 voltage switching frequency

This ratio should be less than 0.75.

If the ratio is greater than above, it means warm-up three way catalyst does not operate properly. Go to "DIAGNOSTIC PROCEDURE " .

NOTE: If the voltage at terminal 16 or 35 does not switch periodically more than 5 times within 10 seconds at step 5, perform trouble diagnosis for "DTC P0133, P0153" first. (see DTC P0133, P0153 H02S1 .)