P0420

DTC P0420, P0430 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 A/F sensor 1 and heated oxygen sensor
2 approaches a specified limit value, the three way catalyst (manifold) malfunction is diagnosed.

On Board Diagnosis Logic:

DTC Confirmation Procedure

NOTE:
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.

WITH CONSULT-III
TESTING CONDITION:
Do not hold engine speed for more than the specified minutes below.
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Turn ignition switch ON.
4. Turn ignition switch OFF and wait at least 10 seconds.
5. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
6. Let engine idle for 1 minute.
7. Select "COOLANT TEMP/S" in "DATA MONITOR" mode with CONSULT-III.
8. Check that "COOLANT TEMP/S" indication is more than 70�C (158�F).
If not, warm up engine and go to next step when "COOLANT TEMP/S" indication reaches 70�C (158�F).
9. Open engine hood.
10. Select "DTC and SRT CONFIRMATION" then "SRT WORK SUPPORT" mode with CONSULT-III.
11. Rev engine between 2,000 and 3,000 rpm and maintain that speed for 3 consecutive minutes, then release the accelerator pedal completely.
If "INCMP" of "CATALYST" changed to "CMPLT", go to step 14.
12. Wait 5 seconds at idle.
13. Rev engine between 2,000 and 3,000 rpm and maintain that speed 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.
14. Check 1st trip DTC.
15. If 1st trip DTC is detected, go to P0420.




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 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 55 [HO2S2 (bank 1) signal] and ground, ECM terminal 74 [HO2S2 (bank 2) signal]
and ground.
7. Keep engine speed at 2,500 rpm constant under no load.
8. Check that the voltage does not vary for more than 5 seconds.
If the voltage fluctuation cycle takes less than 5 seconds, go to EC-1027, "Diagnosis Procedure".
- 1 cycle: 0.6 - 1.0 to 0 - 0.3 to 0.6 - 1.0




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 LEAKAGE
1. Start engine and run it at idle.
2. Listen for an exhaust gas leakage before the three way catalyst (manifold).
OK or NG
OK - GO TO 3.
NG - Repair or replace malfunctioning part.
3.CHECK INTAKE AIR LEAKAGE
Listen for an intake air leakage after the mass air flow sensor.
OK or NG
OK - GO TO 4.
NG - Repair or replace malfunctioning part.
4.CHECK IGNITION TIMING
Check the following items. Refer to Basic Service Procedure.





OK or NG
OK - GO TO 5.
NG - Follow the instructions on Basic Service Procedure.
5.CHECK FUEL INJECTORS
1. Stop engine and then turn ignition switch ON.





2. Check voltage between ECM terminals 21, 22, 23, 40, 41, 42, 44, 63 and ground with CONSULT-III or tester. Refer to Wiring Diagram for fuel injectors, Fuel Injector.

Battery voltage should exist.

OK or NG
OK - GO TO 6.
NG - Perform Diagnosis Procedure.
6.CHECK FUNCTION OF IGNITION COIL-I

CAUTION:
Perform the following procedure in a place with no combustible objects and good ventilation.
1. Turn ignition switch OFF.





2. Remove fuel pump fuse (1) in IPDM E/R (2) to release fuel pressure.

NOTE:
Do not use CONSULT-III 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 approximately 3 seconds, and check whether spark is generated between the spark plug and the grounded metal portion.

Spark should be generated.


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

NOTE:
When the gap is less than 13 mm, 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 non-malfunctioning spark plug.
3. Crank engine for approximately 3 seconds, and recheck whether spark is generated between the spark plug and the grounded metal portion.

Spark should be generated.

OK or NG
OK - GO TO 8.
NG - Check ignition coil, power transistor and their circuits. Refer to Diagnosis Procedure.
8.CHECK SPARK PLUG





Check the initial spark plug for fouling, etc.
OK or NG
OK - Replace spark plug(s) with standard type one(s). For spark plug type, refer to [1][2]Specifications.
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 approximately 3 seconds, and recheck whether spark is generated between the spark plug and the grounded portion.

Spark should be generated.

OK or NG
OK INSPECTION END
NG - Replace spark plug(s) with standard type one(s). For spark plug type, refer to [1][2]Specifications.
10.CHECK FUEL INJECTOR
1. Turn ignition switch OFF.
2. Remove fuel tube assembly. Refer to Component.
Keep fuel hose and all fuel injectors connected to fuel tube.
3. Disconnect all ignition coil harness connectors.
4. Reconnect all fuel injector harness connectors disconnected.
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.
11.CHECK INTERMITTENT INCIDENT
Refer to Diagnosis Procedure.
Trouble is fixed. INSPECTION END
Trouble is not fixed. Replace malfunctioning three way catalyst assembly.