Code No. P0171: Abnormal Fuel System (lean)

OPERATION

Refer to Code No. P0201: No. 1 Injector System .
Refer to Code No. P0202: No. 2 Injector System .
Refer to Code No. P0203: No. 3 Injector System .
Refer to Code No. P0204: No. 4 Injector System .

FUNCTION

If the fuel system goes out of order, the fuel correction value will become larger.
The engine-ECU checks whether the fuel trim value is within a specified range.

TROUBLE JUDGMENT

Check Conditions

Engine coolant temperature is less than 100°C when the engine is started.
Intake air temperature is less than 60°C when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is more than 76°C.
Air flow sensor output is more than 10 g/sec.

Judgement Criterion

Long-term fuel trim is more than +12.5 % for 5 seconds.

Short-term fuel trim is more than +7.0 % for 5 seconds.

Check Conditions

Engine coolant temperature is less than 100°C when the engine is started.
Intake air temperature is less than 60°C when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is more than 76°C.
Airflow sensor output is more than 10 g/sec.

Judgement Criterion

Long-term fuel trim is more than +12.5 % for 5 seconds.

Short-term fuel trim is more than +12.1 % for 5 seconds.

Check Conditions

Engine coolant temperature is more than 100°C when the engine is started.
Intake air temperature is more than 60°C when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is more than 76°C.
Airflow sensor output is more than 10 g/sec.

Judgement Criterion

Long-term fuel trim is more than +12.5 % for 5 seconds.

Short-term fuel trim is more than +17.2 % for 5 seconds.

Check Conditions

Engine coolant temperature is more than 100°C when the engine is started.
Intake air temperature is more than 60°C when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is more than 76°C.
Airflow sensor output is less than 10 g/sec.

Judgement Criterion

Long-term fuel trim is more than +12.5 % for 5 seconds.

Short-term fuel trim is more than +22.3 % for 5 seconds.

Check Conditions

Engine coolant temperature is more than 76°C.
Under the closed loop air/fuel ratio control.

Judgement Criterion

Long-term fuel trim is +12.5 % for 2 seconds.

Short-term fuel trim is +25.0 % for 2 seconds.

PROBABLE CAUSES

Failed intake air temperature sensor
Failed air flow sensor
Failed injector
Air drawn in from gaps in gasket, seals, etc.
Failed engine coolant temperature sensor
Failed manifold absolute pressure sensor
Failed barometric pressure sensor
Exhaust leak
Incorrect fuel pressure
Use of incorrect or contaminated fuel
Harness damage in injector circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check for exhaust leaks

Q. Is the check result normal?

	Go to Step 2 .

	Repair.

STEP 2. Check for intake system vacuum leaks.

Q. Is the check result normal?

	Go to Step 3 .

	Repair.

STEP 3. M.U.T.-III data list

Refer to Data List Reference Table .

Item 5: Intake air temperature sensor
Item 6: Engine coolant temperature sensor
Item 8: Manifold absolute pressure sensor
Item 10: Air flow sensor

Q. Are the check results normal?

	Go to Step 4 .

	Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value (Refer to Inspection Chart for Diagnosis Code ).

STEP 4. M.U.T.-III data list

Refer to Data List Reference Table .

Item BB: Barometric pressure sensor

Q. Is the check result normal?

	Go to Step 5 .

	Replace the engine-ECU.

STEP 5. Connector Check: Injector connector

B-101 (No. 1 injector connector).
B-102 (No. 2 injector connector).
B-103 (No. 3 injector connector).
B-104 (No. 4 injector connector).

Q. Are the check results normal?

	Go to Step 6 .

	Repair or replace the connector.

STEP 6. Check injector itself.

Check injector itself (Refer to ).

Q. Is the check result normal?

	Go to Step 7 .

	Replace the injector.

STEP 7. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?

	Go to Step 8 .

	Repair or replace the connector.

STEP 8. Check harness between injector connector and engine-ECU connector.

Check and repair harness between B-101 (terminal No. 2) No. 1 injector connector and B-08 (terminal No. 2) engine-ECU connector.
Check and repair harness between B-102 (terminal No. 2) No. 2 injector connector and B-08 (terminal No. 3) engine-ECU connector.
Check and repair harness between B-103 (terminal No. 2) No. 3 injector connector and B-08 (terminal No. 18) engine-ECU connector.
Check and repair harness between B-104 (terminal No. 2) No. 4 injector connector and B-08 (terminal No. 19) engine-ECU connector.

Check output line for damage.

Q. Are the check result normal?

	Go to Step 9 .

	Repair the damaged harness wire.

STEP 9. Fuel pressure measurement.

Fuel pressure measurement (Refer to Fuel Pressure Test ).

Q. Is the check result normal?

	Go to Step 10 .

	Repair.

STEP 10. Check for entry of foreign matter (water, kerosene, etc.) into fuel.

Q. Is the check result normal?

	Go to Step 11 .

	Replace the fuel.

STEP 11. Replace the injector.

After replacing the injector, re-check the trouble symptoms.

Q. Is the check result normal?

	Check end.

	Replace the engine-ECU.