P0420

P0420 Three Way Catalyst Function

On Board Diagnosis 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 (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

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 SDT

TESTING CONDITION:

Do not hold engine speed for more than the specified minutes below.
1) Turn ignition switch ON and select "Data list" mode with SDT.
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).

If not, warm up engine and go to next step when "COOLAN TEMP/S" indication reaches to 70 °C (158 °F).
7) Open engine hood.
8) Select "Utility (Readiness test / DTC work support)" then "Readiness test" mode with SDT.
9) Rev engine between 2,500 and 3,500 rpm and hold it for 3 consecutive minutes, then release the accelerator pedal completely.

If "INCMP" of "CATALYST" changed to "CMPLT", go to step 12.
10) Wait 5 seconds at idle.
11) 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).

If not "CMPLT", stop engine and cool it down to less than 70 °C (158 °F) and then retest step 1.
12) Select "DTC check" mode with SDT.
13) Confirm that the 1st trip DTC is not detected.

If the 1st trip DTC is detected, go to "Diagnosis Procedure".

Overall Function Check

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

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 (HO2S2 signal) 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 "Diagnosis Procedure".
- 1 cycle: 0.6 - 1.0 V -> 0 - 0.3 V -> 0.6 - 1.0 V

Diagnosis Procedure

1. CHECK EXHAUST SYSTEM

Visually check exhaust tubes and muffler for dents.

OK or NG
OK
GO TO 2.
NG
Repair or replace.

2. CHECK EXHAUST GAS LEAK

1 Start engine and run it at idle.
2 Listen for an exhaust gas leak before the three way catalyst (manifold).






OK or NG
OK
GO TO 3.
NG
Repair or replace.

3. CHECK INTAKE AIR LEAK

Listen for an intake air leak after the mass air flow sensor.

OK or NG
OK
GO TO 4.
NG
Repair or replace.

4. CHECK IGNITION TIMING

Check the following items. Refer to [Basic Inspection] Basic Inspection.






OK or NG
OK
GO TO 5.
NG
Follow the [Basic Inspection] Basic Inspection.

5. CHECK FUEL INJECTOR

1 Stop engine and then turn ignition switch ON.
2 Check voltage between ECM terminals 22, 23, 41, 42 and ground with SDT or tester.











OK or NG
OK
GO TO 6.
NG
Perform [Fuel Injector Circuit Check] Testing and Inspection.

6. CHECK FUNCTION OF IGNITION COIL-I

CAUTION:
Do the following procedure in the place where ventilation is good without the combustible.

1 Turn ignition switch OFF.
2 Remove fuel pump fuse in IPDM E/R to release fuel pressure.






NOTE:
Do not use SDT to release fuel pressure, or fuel pressure applies again during the following procedure.

3 Start engine.
4 After engine stalls, crank it two or three times to release all fuel pressure.
5 Turn ignition switch OFF.
6 Remove all ignition coil harness connectors to avoid the electrical discharge from the ignition coils.
7 Remove ignition coil and spark plug of the cylinder to be checked.
8 Crank engine for 5 seconds or more to remove combustion gas in the cylinder.
9 Connect spark plug and harness connector to ignition coil.
10 Fix ignition coil using a rope etc. with gap of 13 - 17 mm between the edge of the spark plug and grounded metal portion as shown in the figure.





11 Crank engine for about three seconds, and check whether spark is generated between the spark plug and the grounded metal portion.






CAUTION:
- Never approach to the spark plug and the ignition coil within 50 cm. Be careful not to get an electrical shock while checking, because the electrical discharge voltage becomes 20 kV or more.
- It might cause to damage the ignition coil if the gap of more than 17 mm is taken.

NOTE:
When the gap is less than 13 mm, the spark might be generated even if the coil is malfunctioning.

OK or NG
OK
GO TO 10.
NG
GO TO 7.

7. CHECK FUNCTION OF IGNITION COIL-II

1 Turn ignition switch OFF.
2 Disconnect spark plug and connect a known-good spark plug.
3 Crank engine for about 3 seconds, and recheck whether spark is generated between the spark plug and the grounded metal portion.






OK or NG
OK
GO TO 8.
NG
Check ignition coil, power transistor and their circuits. Refer to [Ignition Coil: Removal and Installation] Testing and Inspection.

8. CHECK SPARK PLUG

Check the initial spark plug for fouling, etc. Refer to Removal and Installation.






OK or NG
OK
Replace spark plug(s) with standard type one(s).
NG
1 Repair or clean spark plug.
2 GO TO 9.

9. CHECK FUNCTION OF IGNITION COIL-III

1 Reconnect the initial spark plugs.
2 Crank engine for about 3 seconds, and recheck whether spark is generated between the spark plug and the grounded portion.






OK or NG
OK
INSPECTION END
NG
Replace spark plug(s) with standard type one(s). For spark plug type. Refer to [Ignition Coil: Removal and Installation] Removal and Installation.

10. CHECK FUEL INJECTOR

1 Turn ignition switch OFF.
2 Remove fuel injector assembly. Refer to [Fuel Injector and Fuel Tube: Removal and Installation [QR25DE] Removal and Installation ].
Keep fuel hose and all fuel injectors connected to fuel injector gallery.
3 Reconnect all fuel injector harness connectors.
4 Disconnect all ignition coil harness connectors.
5 Turn ignition switch ON.
check that fuel does not drip from fuel injector.

OK or NG
OK (Does not drip)
GO TO 11.
NG (Drips)
Replace the fuel injector(s) from which fuel is dripping. Refer to [Fuel Injector and Fuel Tube: Removal and Installation [QR25DE] Removal and Installation ].

11. CHECK INTERMITTENT INCIDENT

Perform [Service Information for Electrical Incident: Intermittent Incident] Service Information for Electrical Incident: Intermittent Incident.

Trouble is fixed
INSPECTION END
Trouble is not fixed
Replace three way catalyst (manifold). Refer to [Exhaust Manifold and Three Way Catalyst: Exploded View [QR25DE] Exhaust Manifold and Three Way Catalyst Exploded View ].