Diagnosis Procedure

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

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Is exhaust gas leak detected?

YES

Repair or replace.

NO

GO TO 2.

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

Is intake air leak detected?

YES

Repair or replace.

NO

GO TO 3.

1. Turn ignition switch OFF.
2. Disconnect corresponding A/F sensor 1 harness connector.
3. Disconnect ECM harness connector.
4. Check the continuity between A/F sensor 1 harness connector and ECM harness connector.

   DTC	A/F sensor 1			ECM		Continuity
   	Bank	Connector	Terminal	Connector	Terminal
   P0172	1	F72	3	F79	102	Existed
   			4		101
   P0175	2	F73	3		111
   			4		107

5. Check the continuity between A/F sensor 1 harness connector and ground, or ECM harness connector and ground.

   DTC	A/F sensor 1			--	Continuity
   	Bank	Connector	Terminal
   P0172	1	F72	3	Ground	Not existed
   			4
   P0175	2	F73	3
   			4

   DTC	ECM			--	Continuity
   	Bank	Connector	Terminal
   P0172	1	F79	101	Ground	Not existed
   			102
   P0175	2		107
   			111

6. Also check harness for short to power.

Is the inspection result normal?

YES

GO TO 4.

NO

Repair or replace error-detected parts.

1. Release fuel pressure to zero. Refer to Work Procedure .
2. Install fuel pressure gauge and check fuel pressure. Refer to Work Procedure .

Is the inspection result normal?

YES

GO TO 5.

NO

Replace "fuel level sensor, fuel filter and fuel pump assembly". Refer to Removal and Installation .

With CONSULT

1. Install all removed parts.
2. Check "MASS AIR FLOW SENSOR (Hz)" in "Data Monitor" mode of "ENGINE".

   For specification, refer to Mass Air Flow Sensor .

With GST

1. Install all removed parts.
2. Check mass air flow sensor signal in "Service $01" with GST.

   For specification, refer to Mass Air Flow Sensor .

Is the measurement value within the specification?

YES

GO TO 6.

NO

Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or grounds. Refer to Diagnosis Procedure .

With CONSULT

1. Start engine.
2. Perform "POWER BALANCE" in "Active Test" mode of "ENGINE".
3. Make sure that each circuit produces a momentary engine speed drop.

Without CONSULT

1. Start engine and let it idle.
2. Listen to each fuel injector operating sound.

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   Clicking sound should be heard.

Is the inspection result normal?

YES

INSPECTION END

NO

Perform trouble diagnosis for FUEL INJECTOR, refer to Diagnosis Procedure .