Three Way Catalyst Function
P0420 THREE WAY CATALYST FUNCTION
DTC Logic
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 (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.
DTC CONFIRMATION PROCEDURE
1. PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always perform the following 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 hold engine speed for more than the specified minutes below.
- GO TO 2.
2. PERFORM DTC CONFIRMATION PROCEDURE
CAUTION:
Always drive vehicle in safe manner according to traffic conditions and obey all traffic laws.
With CONSULT
1.Start engine and warm it up to the normal operating temperature.
2.Repeat the following procedure 3 times.
-Drive vehicle at a speed of 80 km/h (50 MPH) or more for at least 3 consecutive minutes.
NOTE:
Keep the vehicle speed as steady as possible during the cruising.
-Stop vehicle with engine running.
NOTE:
Never turn ignition switch OFF.
3.Select "DTC & SRT CONFIRMATION" then "SRT WORK SUPPORT" mode with CONSULT.
4.Drive vehicle at a speed of 80 km/h (50 MPH) or more until "INCMP" of "CATALYST" changes to "CMPLT"
NOTE:
-Keep the vehicle speed as steady as possible during the cruising.
-It will take at most 3 minutes until "INCMP" of "CATALYST" changes to "CMPLT".
5.Check 1st trip DTC.
With GST
1.Start engine and warm it up to the normal operating temperature.
2.Repeat the following procedure 3 times.
-Drive vehicle at a speed of 80 km/h (50 MPH) or more for at least 3 consecutive minutes.
NOTE:
Keep the vehicle speed as steady as possible during the cruising.
-Stop vehicle with engine running.
NOTE:
Never turn ignition switch OFF.
3.Check 1st trip DTC.
Is 1st trip DTC detected?
YES- Go to "Diagnosis Procedure" .
NO- INSPECTION END
Component Function Check
1. PERFORM COMPONENT FUNCTION CHECK
Without CONSULT
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.Check the voltage between ECM harness connector terminals under the following condition.
Is the inspection result normal?
YES- INSPECTION END
NO- Go to "Diagnosis Procedure" .
Diagnosis Procedure
1. CHECK EXHAUST SYSTEM
Visually check exhaust tubes and muffler for dents.
Is the inspection result normal?
YES- GO TO 2.
NO- 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).
Is exhaust gas leak detected?
YES- Repair or replace.
NO- GO TO 3.
3. CHECK INTAKE AIR LEAK
Listen for an intake air leak after the mass air flow sensor.
Is intake air leak detected?
YES- Repair or replace.
NO- GO TO 4.
4. CHECK IGNITION TIMING
Check the following items. Refer to "BASIC INSPECTION : Special Repair Requirement" Basic Inspection.
Is the inspection result normal?
YES- GO TO 5.
NO- Follow the "BASIC INSPECTION : Special Repair Requirement" Basic Inspection.
5. CHECK FUEL INJECTOR
1.Stop engine and then turn ignition switch ON.
2.Check the voltage between ECM harness connector and ground.
Is the inspection result normal?
YES- GO TO 6.
NO- Perform "Diagnosis Procedure" Component Test.
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 in IPDM E/R to release fuel pressure. For the fuse number, refer to "Wiring Diagram ENGINE CONTROL SYSTEM -" Except For Mexico. For the fuse arrangement, refer to "Fuse, Connector and Terminal Arrangement" IPDM E/R.
NOTE:
Do not use CONSULT 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. Refer to "Removal and Installation" Removal And Installation.
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 (0.52 0.66 in) 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:
- During the operation, always stay 0.5 m (19.7 in) or more away from the spark plug and the ignition coil. 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 (0.66 in) is made.
NOTE:
When the gap is less than 13 mm (0.52 in), a the spark might be generated even if the coil is malfunctioning.
Is the inspection result normal?
YES- GO TO 10.
NO- 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.
Is the inspection result normal?
YES- GO TO 8.
NO- Check ignition coil, power transistor and their circuits. Refer to "Diagnosis Procedure" Component Test.
8. CHECK SPARK PLUG
Check the initial spark plug for fouling, etc.
Is the inspection result normal?
YES- Replace spark plug(s) with standard type one(s). For spark plug type, refer to "Removal and Installation" Removal And Installation.
NO- Repair or clean spark plug. Then 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.
Is the inspection result normal?
YES- INSPECTION END
NO- Replace spark plug(s) with standard type one(s). For spark plug type, refer to "Removal and Installation" Removal And Installation.
10. CHECK FUEL INJECTOR
1.Turn ignition switch OFF.
2.Remove fuel injector assembly.
Refer to "Removal and Installation" Removal And Installation.
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.
Does fuel drip from fuel injector?
YES- GO TO 11.
NO- Replace the fuel injector(s) from which fuel is dripping. Refer to "Removal and Installation" Removal And Installation.
11. CHECK INTERMITTENT INCIDENT
Refer to "Intermittent Incident" Intermittent Incident.
Is the trouble fixed?
YES- INSPECTION END
NO- Replace three way catalyst assembly. Refer to "Removal and Installation" Removal And Installation.