Overall Function Check

Use this procedure to check the overall function of the warm-up three way catalyst. During this check, a 1st trip DTC might not be confirmed.

Without CONSULT





(1) Start engine and warm it up to normal operating temperature.
(2) Set voltmeters probes between ECM terminals 50 (front heated oxygen sensor right bank signal), 51 (front heated oxygen sensor left bank signal) and engine ground and ECM terminals 56 (rear heated oxygen sensor right bank signal), 57 (rear heated oxygen sensor left bank signal) and engine ground.
(3) Keep engine speed at 2,000 rpm constant under no load.





(4) Make sure that the voltage switching frequency (high & low) between ECM terminals 56 and engine ground or 57 and engine ground is very less than that of ECM terminals 50 and engine ground or 51 and engine ground.
Switching frequency ratio = A/B
A: Rear heated oxygen sensor voltage switching frequency
B: Front heated oxygen sensor 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.

NOTE: If the voltage at terminal 50 or 51 does not switch periodically more than 5 times within 10 seconds at step 4, perform trouble diagnosis for "DTC P0133, P0153" first.