P0420
DTC P0420 THREE WAY CATALYST FUNCTIONOn Board Diagnosis Logic
A/T MODELS ULEV AND M/T MODELS
The ECM monitors the switching frequency ratio of heated oxygen sensor 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 sensor 1 and 2 approaches a specified limit value, the three way catalyst (manifold) malfunction is diagnosed.
A/T MODELS EXCEPT ULEV
The ECM monitors the switching frequency ratio of air fuel ratio (A/F) sensor 1 and heated oxygen sensor 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 air fuel ratio (A/F) sensor 1 and heated oxygen sensor 2 approaches a specified limit value, the three way catalyst (manifold) malfunction is diagnosed.
DTC Confirmation Procedure
A/T MODELS ULEV AND M/T MODELS
NOTE: If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at least 10 seconds before conducting the next test.
With CONSULT-II
TESTING CONDITION:
- Open engine hood before conducting the following procedure.
- Do not hold engine speed for more than the specified minutes below.
1. Turn ignition switch ON and select "DATA MONITOR" mode with CONSULT-II.
2. Start engine and warm it up to the normal operating temperature.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
5. Let engine idle for 1 minute.
6. Make sure that "COOLANT TEMP/S" indicates more than 70 °C (158 °F).
7. Open engine hood.
8. Select "DTC & SRT CONFIRMATION" then "SRT WORK SUPPORT" mode with CONSULT-II.
9. 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 7
10. Wait 5 seconds at idle.
11. 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", stop engine and cool it down to less than 70 °C (158 °F) and then retest from step 1.
12. Select "SELF-DIAG RESULTS" mode with CONSULT-II.
13. Confirm that the 1st trip DTC is not detected.
If the 1st trip DTC is detected, go to "Diagnostic Procedure" below.
A/T MODELS EXCEPT ULEV
NOTE: If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at least 10 seconds before conducting the next test.
With CONSULT-II
TESTING CONDITION:
Do not hold engine speed for more than the specified minutes below.
1. Turn ignition switch ON and select "DATA MONITOR" mode with CONSULT-II.
2. Start engine and warm it up to normal operating temperature.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
5. Let engine idle for 1 minute.
6. Make sure that "COOLAN TEMP/S" indicates more than 70 °C (158 °F).
7. Open engine hood.
8. Select "DTC & SRT CONFIRMATION" then "SRT WORK SUPPORT" mode with CONSULT-II.
9. Rev engine up to 2,500 to 3,500 rpm and hold it for 3 consecutive minutes, then release the accelerator pedal completely.
If "CMPLT" of "CATALYST" changed to "COMPLT", go to STEP 12.
10. Wait 5 seconds at idle.
11. Rev engine up to 2,000 to 3,000 rpm and maintain it until "IMCMP" of "CATALYST" changes to "CMPLT" (it will take approximately 5 minutes).
If not "CMPLT", stop engine and cool it down to less than 70 °C (158 °F) and then retest step 1.
12. Select "SELF-DIAG RESULTS" mode with CONSULT-II.
13. 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.
A/T MODELS ULEV AND M/T MODELS
With GST
1. Start engine and warm it up to the normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
4. Let engine idle for 1 minute.
5. Set voltmeters probes between ECM terminal 35 (HO2S1 signal) and ground, and ECM terminal 74 (HO2S2 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 terminal 74 and engine ground is very less than that of ECM terminal 35 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 does not operate properly. go to "Diagnostic Procedure" below.
NOTE: If the voltage at terminal 35 does not switch periodically more than 5 times within 10 seconds at step 7, perform trouble diagnosis for "DTC P0133" first. P0133
AT MODELS EXCEPT ULEV
With GST
1. Start engine and warm it up to the normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
4. Let engine idle for 1 minute.
5. Open engine hood.
6. Set voltmeter probe between ECM terminal 74 and ground.
7. Keep engine speed at 2,500 rpm constant under no load.
8. Make sure that the voltage does not vary for more than 5 seconds.
If the voltage fluctuation cycle takes less than 5 seconds, go to "Diagnostic Procedure" below.
- 1 cycle: 0.6 - 1.0 V -> 0 - 0.3 V -> 0.6 - 1.0 V
Diagnostic Procedure
Diagnostic Procedure (Steps 1 - 4):
Diagnostic Procedure (Steps 5 - 6):
Diagnostic Procedure (Steps 7 - 11):
A/T MODELS ULEV AND M/T MODELS
Diagnostic Procedure (Steps 1 - 4):
Diagnostic Procedure (Steps 5 - 6):
Diagnostic Procedure (Steps 7 - 11):
A/T MODELS EXCEPT ULEV