Nissan Sentra. Manual - part 397

EC-284

< DTC/CIRCUIT DIAGNOSIS >

[MRA8DE]

P0420 THREE WAY CATALYST FUNCTION

11. Rev engine up to 2,000 to 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 screen?

CMPLT >> GO TO 5.

INCMP >> GO TO 3.

3.

PERFORM DTC CONFIRMATION PROCEDURE-2

1. Wait 5 seconds at idle.

2. Rev engine up to 2,000 to 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 5.

NO

>> GO TO 4.

4.

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 2.

5.

PERFORM DTC CONFIRMATION PROCEDURE-3

Check 1st trip DTC.
Is 1st trip DTC detected?

YES

>> Proceed to 

EC-285, "Diagnosis Procedure"

.

NO

>> INSPECTION END

6.

PERFORM COMPONENT FUNCTION CHECK

Perform component function check. Refer to 

EC-284, "Component Function Check"

.

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

>> Proceed to 

EC-285, "Diagnosis Procedure"

.

Component Function Check

INFOID:0000000009758531

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. Restart 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 as per the following condition.

Is the inspection result normal?

ECM

Condition

Voltage (V)

Connector

+

–

Terminal

F24

22

23

Keeping engine speed at 
2500 rpm constant under no 
load

The voltage fluctuation cy-
cle takes more than 5 sec-
onds.
• 1 cycle: 0.6 - 1.0 

→ 0 - 0.3 

→ 0.6 - 1.0

P0420 THREE WAY CATALYST FUNCTION

EC-285

< DTC/CIRCUIT DIAGNOSIS >

[MRA8DE]

C

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EC

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YES

>> INSPECTION END

NO

>> Proceed to 

EC-285, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000009758532

1.

CHECK EXHAUST SYSTEM

Visually check exhaust tubes and muffler for dent.
Is the inspection result normal?

YES

>> GO TO 2.

NO

>> Repair or replace error-detected parts.

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 error-detected parts.

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 error-detected parts.

NO

>> GO TO 4.

4.

CHECK IGNITION TIMING AND IDLE SPEED

Check the following items.

• Ignition timing (Refer to 

EC-480, "Inspection"

.)

• Idle speed (Refer to 

EC-479, "Inspection"

.)

Is the inspection result normal?

YES

>> GO TO 5.

NO

>> Perform “BASIC INSPECTION”. Refer to 

EC-131, "Work Procedure"

.

5.

CHECK FUEL INJECTOR

Check the fuel injector. Refer to 

EC-450, "Component Function Check"

.

Is the inspection result normal?

YES

>> GO TO 6.

NO

>> Perform 

EC-450, "Diagnosis Procedure"

.

6.

CHECK FUNCTION OF IGNITION COIL-1

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 CONSULT to release fuel pressure, or fuel pressure applies again during the following proce-

dure.

3. Start engine.

4. After engine stalls, crank it two or three times to release all fuel pressure.

PBIB1216E

EC-286

< DTC/CIRCUIT DIAGNOSIS >

[MRA8DE]

P0420 THREE WAY CATALYST FUNCTION

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 (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 about 3 seconds, and check whether spark is

generated between the spark plug and the grounded metal por-

tion.

CAUTION:

• Do not approach to the spark plug and the ignition coil

within 50 cm (19.7 in). 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 taken.

NOTE:

When the gap is less than 13 mm (0.52 in), the spark might be generated even if the coil is mal-

functioning.

Is the inspection result normal?

YES

>> GO TO 10.

NO

>> GO TO 7.

7.

CHECK FUNCTION OF IGNITION COIL-2

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.

Is the inspection result normal?

YES

>> GO TO 8.

NO

>> Check ignition coil, power transistor and their circuits. Refer to 

EC-456, "Diagnosis Procedure"

.

8.

CHECK SPARK PLUG

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

EM-13, "Inspec-

tion"

.

Is the inspection result normal?

YES

>> Replace spark plug(s) with standard type one(s). For

spark plug type, refer to 

EM-118, "Spark Plug"

.

NO

>> 1. Repair or clean spark plug. Refer to 

EM-45,

"Removal and Installation"

.

2. GO TO 9.

9.

CHECK FUNCTION OF IGNITION COIL-3

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.

Is the inspection result normal?

YES

>> INSPECTION END

Spark should be generated.

JMBIA0066GB

Spark should be generated.

SEF156I

Spark should be generated.

P0420 THREE WAY CATALYST FUNCTION

EC-287

< DTC/CIRCUIT DIAGNOSIS >

[MRA8DE]

C

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EC

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NO

>> Replace spark plug(s) with standard type one(s). For spark plug type, refer to 

EM-118, "Spark

Plug"

.

10.

CHECK FUEL INJECTOR

1. Turn ignition switch OFF.

2. Remove fuel injector assembly. Refer to 

EM-40, "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 

EM-40, "Removal and Installa-

tion"

.

11.

CHECK INTERMITTENT INCIDENT

Check intermittent incident. Refer to 

GI-39, "Intermittent Incident"

.

Is the trouble fixed?

YES

>> INSPECTION END

NO

>> Replace three way catalyst assembly. Refer to 

EX-5, "Exploded View"

.