P0420

DTC P0420 THREE WAY CATALYST FUNCTION







On Board Diagnosis Logic
The ECM monitors the switching frequency ratio of heated oxygen sensors 1 and 2.

A three way catalyst (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.

When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst (Manifold) malfunction is diagnosed.

DTC Confirmation Procedure

NOTE: If "DTC Confirmation Procedure" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test.

WITH CONSULT-II

TESTING CONDITION
- Do not hold engine speed for more than the specified minutes below.

1. Start engine and warm it up to the normal operating temperature.
2. Turn ignition switch "OFF" and wait at least 5 seconds.
3. Start engine and keep the engine speed at between 3,500 and 4,000 rpm for at least one minute under no load.
4. Let engine idle for one minute.
5. Open engine hood.




6. Select "DTC & SRT CONFIRMATION" then "SRT WORK SUPPORT" mode with CONSULT-II.
7. Rev engine up to 2,000 to 3,000 rpm and hold it for 3 consecutive minutes then release the accelerator pedal completely. If "INCMP" of "CATALYST" changed to "COMPLT", go to step 10.
8. Wait 5 seconds at idle.




9. Rev engine up to 2,000 to 3,000 rpm and maintain it until "INCMP" of "CATALYST" changes to "CMPLT" (It will take approximately 5 minutes).
If not "CMPLT", perform the following.




10. Select "SELF-DIAG RESULTS" mode with CONSULT-II.
11. Confirm that the 1st trip DTC is not detected.
If the 1st trip DTC is detected, go to "Diagnostic Procedure" below.

Overall Function Check
Use this procedure to check the overall function of the three way catalyst (manifold). During this check, a DTC might not be confirmed.

CAUTION: Always drive vehicle at a safe speed.

WITH GST
1. Start engine and warm it up to the normal operation temperature.
2. Turn ignition switch "OFF" and wait at least 10 seconds.
3. Start engine and keep the engine speed at between 3,500 and 4,000 rpm for at least one minute under no load.
4. Let engine idle for one minutes.




5. Set voltmeters probes between ECM terminals 50 [HO2S1 (bank 1) signal], 51 [HO2S1 (bank 2) signal] and engine ground, and ECM terminals 56 [HO2S2 (bank 1) signal], 57 [HO2S2 (bank 2) signal] and engine ground.
6. Keep engine speed at 2,000 rpm constant under no load.




7. 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: 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 three way catalyst (manifold) does not operate properly. Go to "Diagnostic Procedure" below.

NOTE: If the voltage at terminal 50 or 51 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 HO2S1".)

Diagnostic Procedure

Diagnostic Procedure Step 1 - 4:

Diagnostic Procedure Step 5 - 7:

Diagnostic Procedure Step 8 - 9: