DTC DETECTION LOGIC The ECM monitors the switching frequency ratio of air fuel ratio (A/F) sensor 1 and heated oxygen sensor 2. A three way catalyst 1 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 A/F sensor 1 and heated oxygen sensor 2 approaches a specified limit value, the three way catalyst 1 malfunction is diagnosed.

DTC No. | Trouble diagnosis name | DTC detecting condition | Possible cause
P0420 | Catalyst system efficiency below threshold (bank 1) |

- Three way catalyst (manifold) does not operate properly.
- Three way catalyst (manifold) does not have enough oxygen storage capacity.

- Three way catalyst (manifold)
- Exhaust tube
- Intake air leaks
- Fuel injector
- Fuel injector leaks
- Spark plug
- Improper ignition timing

P0430 | Catalyst system efficiency below threshold (bank 2)

DTC CONFIRMATION PROCEDURE
1.INSPECTION START
Do you have CONSULT-III?
Do you have CONSULT-III?
YES>>GO TO 2.
NO>>GO TO 7.
2.PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.

1. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.

TESTING CONDITION:
Do not maintain engine speed for more than the specified minutes below.
>>GO TO 3.
3.PERFORM DTC CONFIRMATION PROCEDURE-I
With CONSULT-III

1. Turn ignition switch ON and select “DATA MONITOR” mode with CONSULT-III.
2. Start engine and warm it up to the normal operating temperature.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Turn ignition switch ON.
5. Turn ignition switch OFF and wait at least 10 seconds.
6. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
7. Let engine idle for 1 minute.
8. Check that “COOLAN TEMP/S” indicates more than 70°C (158°F).If not, warm up engine and go to next step when “COOLAN TEMP/S” indication reaches 70°C (158°F).
9. Open engine hood.
10. Select “DTC & SRT CONFIRMATION” then “SRT WORK SUPPORT” mode with CONSULT-III.
11. Rev engine between 2,000 and 3,000 rpm and hold it for 3 consecutive minutes then release the accelerator pedal completely.
12. Check the indication of “CATALYST”.

Which is displayed on CONSULT-III screen?
CMPLT>>GO TO 6.
INCMP>>GO TO 4.
4.PERFORM DTC CONFIRMATION PROCEDURE-II

1. Wait 5 seconds at idle.
2. Rev engine between 2,000 and 3,000 rpm and maintain it until “INCMP” of “CATALYST” changes to “CMPLT” (It will take approximately 5 minutes).

Does the indication change to “CMPLT”?
YES>>GO TO 6.
NO>>GO TO 5.
5.PERFORM DTC CONFIRMATION PROCEDURE AGAIN

1. Stop engine and cool it down to less than 70°C (158°F).
2. Perform DTC CONFIRMATION PROCEDURE again.

>> GO TO 3.
6.PERFORM DTC CONFIRMATION PROCEDURE-III
Check 1st trip DTC.
Is 1st trip DTC detected?
YES>>Go to Diagnosis Procedure (GT-R certified NISSAN dealer).
NO>>INSPECTION END
7.PERFORM COMPONENT FUNCTION CHECK
Perform component function check. Refer to Component Function Check (GT-R certified NISSAN dealer).
NOTE：
Use component function check to check the overall function of the three way catalyst (manifold). During this check, a 1st trip DTC might not be confirmed.
Is the inspection result normal?
YES>>INSPECTION END
NO>>Go to Diagnosis Procedure (GT-R certified NISSAN dealer).