P0420, P0430 THREE WAY CATALYST FUNCTION

VR38

P0420 P0430

DTC Logic
Component Function Check
Diagnosis Procedure

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 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

2.PRECONDITIONING

3.PERFORM DTC CONFIRMATION PROCEDURE-I

4.PERFORM DTC CONFIRMATION PROCEDURE-II

5.PERFORM DTC CONFIRMATION PROCEDURE AGAIN

6.PERFORM DTC CONFIRMATION PROCEDURE-III

7.PERFORM COMPONENT FUNCTION CHECK

Component Function Check

1.PERFORM COMPONENT FUNCTION CHECK

Diagnosis Procedure

1.CHECK EXHAUST SYSTEM

2.CHECK EXHAUST GAS LEAK

3.CHECK INTAKE AIR LEAK

4.CHECK IDLE SPEED AND IGNITION TIMING

5.CHECK FUEL INJECTORS

6.CHECK FUNCTION OF IGNITION COIL-I

■ CAUTION ■
Perform the following procedure in a place with no combustible objects and good ventilation.

Turn ignition switch OFF.
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.
Start engine.
After engine stalls, crank it two or three times to release all fuel pressure.
Turn ignition switch OFF.
Remove all ignition coil harness connectors to avoid the electrical discharge from the ignition coils.
Remove ignition coil and spark plug of the cylinder to be checked.
Crank engine for 5 seconds or more to remove combustion gas in the cylinder.
Connect spark plug and harness connector to ignition coil.
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.
Crank engine for about 3 seconds, and check whether spark is generated between the spark plug and the grounded metal portion.
Spark should be generated.

■ CAUTION ■
Do not place to the spark plug and the ignition coil within 50 cm (19.7 in) each other. Be careful not to get an electrical shock while checking, because the electrical discharge voltage becomes 20 kV or more.
It might 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 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

8.CHECK SPARK PLUG

9.CHECK FUNCTION OF IGNITION COIL-III

10.CHECK FUEL INJECTOR

11.CHECK INTERMITTENT INCIDENT

DTC	ECM			Condition	Voltage
	Connector	+	–
		Terminal	Terminal
P0420	F102	73 [HO2S2 (bank 1)]	70	Keeping engine speed at 2,500 rpm constant under no load	The voltage fluctuation cycle takes more than 5 seconds. 1 cycle: 0.6 - 1.0 → 0 - 0.3 → 0.6 - 1.0
P0430		77 [HO2S2 (bank 2)]

ECM				Voltage
+		–
Connector	Terminal	Connector	Terminal
F101	17	M107	128	Battery voltage
	21
	25
	37
	41
	45