P0171
DTC P0171: System too Lean (bank 1)Injector Circuit - Cylinder 1 Part 1:
Injector Circuit - Cylinder 1 Part 2:
Injector Circuit - Cylinder 3 Part 1:
Injector Circuit - Cylinder 3 Part 2:
Injector Circuit - Cylinder 5 Part 1:
Injector Circuit - Cylinder 5 Part 2:
Fuel Trim Circuit
CIRCUIT OPERATION
The injector power is supplied from the injector relay (terminal No. 3).
The ECM controls the injector by turning the power transistor in the ECM "ON" and "OFF".
TECHNICAL DESCRIPTION
If a malfunction occurs in the fuel system, the fuel trim value becomes too large.
The ECM checks whether the fuel trim value is within a specified range.
DESCRIPTIONS OF MONITOR METHODS
Right bank air/fuel learning value (long time fuel trim) and air/fuel feedback integral value (short time fuel trim) are too lean.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
Misfire monitor
Sensor (The sensor below is determined to be normal)
Mass airflow sensor
Engine coolant temperature sensor
Intake air temperature sensor
Barometric pressure sensor
Throttle position sensor
DTC SET CONDITIONS
Logic Flow Chart:
Logic Flow Chart
Check Conditions
Engine coolant temperature is lower than 100 °C (212 °F) when the engine is started.
Intake air temperature is lower than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 76 °C (169 °F).
Mass airflow sensor output is 12 g/sec or more.
Judgement Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds.
or
Short-term fuel trim has continued to be higher than +7.4 percent for 5 seconds.
Check Conditions
Engine coolant temperature is lower than 100 °C (212 °F) when the engine is started.
Intake air temperature is lower than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 76 °C (169 °F).
Mass airflow sensor output is 12 g/sec or less.
Judgement Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds.
or
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds.
Check Conditions
Engine coolant temperature is higher than 100 °C (212 °F) when the engine is started.
Intake air temperature is higher than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 76 °C (169 °F).
Mass airflow sensor output is 12 g/sec or more.
Judgement Criteria
Long-term fuel trim has continued to be higher than +12.5 percent or 5 seconds.
or
Short-term fuel trim has continued to be higher than +17.6 percent for 5 seconds.
Check Conditions
Engine coolant temperature is higher than 100 °C (212 °F) when the engine is started.
Intake air temperature is higher than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 76 °C (169 °F).
Mass airflow sensor output is 12 g/sec or less.
Judgement Criteria
Long-term fuel trim has continued to be higher than +12.5 percent or 5 seconds.
or
Short-term fuel trim has continued to be higher than +22.3 percent for 5 seconds.
Check Conditions
Engine coolant temperature is higher than 76 °C (169 °F).
Under the closed loop air/fuel ratio control.
Judgement Criteria
Long-term fuel trim has continued to be +12.5 percent for 2 seconds.
or
Short-term fuel trim has continued to be +25.0 percent for 2 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 22. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
Mass airflow sensor failed.
Injector (Number 1, 3, 5) failed.
Incorrect fuel pressure.
Air drawn in from gaps in gasket, seals, etc.
Intake air temperature sensor failed.
Manifold absolute pressure sensor failed.
Exhaust leak.
Use of incorrect or contaminated fuel.
Harness damage.
Connector damage.
ECM failed.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
STEP 1. Using scan tool MB991958, check data list item 10: Mass Airflow Sensor.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991958 to the data reading mode for item 10, Mass Airflow Sensor.
4. Warm up the engine to normal operating temperature: 80 °C to 95 °C (176 °F to 203 °F).
When idling, between 1,350 and 1,670 millivolts.
When 2,500 r/min, between 1,620 and 2,020 millivolts.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 2.
NO: Refer to DTC P0101 - Mass Airflow Circuit Range/ Performance Problem, DTC P0102 - Mass Airflow Circuit Low Input, DTC P0103 - Mass Airflow Circuit High Input.
STEP 2. Using scan tool MB991958, check data list item 5: Intake Air Temperature Sensor.
1. Turn the ignition switch to the "ON" position.
2. Set scan tool MB991958 to the data reading mode for item 5, Intake Air Temperature Sensor.
The intake air temperature and temperature shown with the scan tool should approximately match.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 3.
NO: Refer to DTC P0111 - Intake Air Temperature Circuit Range/Performance Problem, DTC P0112 - Intake Air Temperature Circuit Low Input, DTC P0113 - Intake Air Temperature Circuit High Input.
STEP 3. Using scan tool MB991958, check data list item 6: Engine Coolant Temperature Sensor.
1. Turn the ignition switch to the "ON" position.
2. Set scan tool MB991958 to the data reading mode for item 6, Engine Coolant Temperature Sensor.
The engine coolant temperature and temperature shown with the scan tool should approximately match.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 4.
NO: Refer to DTC P0116 - Engine Coolant Temperature Circuit Range/Performance Problem, DTC P0117 - Engine Coolant Temperature Circuit Low Input.
STEP 4. Using scan tool MB991958, check data list item 8: Manifold Absolute Pressure Sensor.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958 to the data reading mode for item 8, Manifold Absolute Pressure Sensor.
When altitude is 0 m (0 foot), 101 kPa (29.8 in.Hg).
When altitude is 600 m (1,969 feet), 95 kPa (28.1 in.Hg).
When altitude is 1,200 m (3,937 feet), 88 kPa (26.0 in.Hg).
When altitude is 1,800 m (5,906 feet), 81 kPa (23.9 in.Hg).
4. Start the engine.
When the engine is idling, 16 - 36 kPa (4.7 - 10.6 in.Hg).
When the engine is suddenly revved, manifold absolute pressure varies.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 5.
NO: Refer to DTC P0106 - Manifold Absolute Pressure Circuit Range / Performance Problem, DTC P0107 - Manifold Absolute Pressure Circuit Low Input, DTC P0108 -Manifold Absolute Pressure Circuit High Input.
STEP 5. Check the fuel pressure.
Refer to On-vehicle Service - Fuel Pressure Test. Testing and Inspection
Q: Is the fuel pressure normal?
YES: Go to Step 6.
NO: Repair it. Then go to Step 16.
STEP 6. Check for harness connector B-21 at the intermediate connector and harness connector B-10 at the ECM for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 7.
NO: Repair it. Then go to Step 16.
STEP 7. Measure the injector supply voltage at the intermediate connector harness B-21 and ground.
1. Disconnect the intermediate connector B-21 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between each male connector side terminal and ground.
a. Connector B-21 (terminal No. 7) and ground.
b. Connector B-21 (terminal No. 8) and ground.
c. Connector B-21 (terminal No. 9) and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage battery positive voltage?
YES: Go to Step 8.
NO: Repair it. Then go to Step 16.
STEP 8. Check the right bank injector resistance at the intermediate connector B-21.
1. Disconnect the intermediate connector B-21.
2. Measure the resistance between each male connector side terminal.
a. Measure the resistance between terminal No. 6 and No. 7 at No. 1 cylinder injector.
b. Measure the resistance between terminal No. 6 and No. 8 at No. 3 cylinder injector.
c. Measure the resistance between terminal No. 6 and No. 9 at No. 5 cylinder injector.
- Resistance should be between 10.5 and 13.5 ohms [at 20 °C (68 °F)].
Q: Is the measured resistance between 10.5 and 13.5 ohms [at 20 °C (68 °F)]?
YES: Go to Step 11.
NO: Go to Step 9.
STEP 9. Check for harness connector B-101, B-103, B-104 at right bank injector for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Then go to Step 16.
STEP 10. Check the right bank injector.
1. Remove the intake manifold.
2. Disconnect the right bank injector connector B-101, B-103, B-104.
3. Measure the resistance between injector side connector terminal No. 1 and No. 2.
Standard value: 10.5 - 13.5 ohms [at 20 °C (68 °F)]
Q: Is the measured resistance between 10.5 and 13.5 ohms [at 20 °C (68 °F)]?
YES: Repair harness wire between injector intermediate connector and right bank injector connector because of harness damage. Then go to Step 16.
NO: Replace the injector. Then go to Step 16.
STEP 11. Check for harness between the right bank injector connector B-101, B-103, B-104 and the ECM connector B-10.
1. Remove the intake manifold.
2. Disconnect the right bank injector connector B-101, B-103, B-104 and the ECM connector B-10.
3. Measure the resistance between the right bank injector connector B-101, B-103, B-104 and the ECM connector B-10.
a. Connector B-101 (terminal No. 2) and connector B-10 (terminal No. 2) at No. 1 cylinder injector.
b. Connector B-103 (terminal No. 2) and connector B-10 (terminal No. 18) at No. 3 cylinder injector.
c. Connector B-104 (terminal No. 2) and connector B-10 (terminal No.50) at No. 5 cylinder injector.
- Should be less than 2 ohms.
Q:Is the harness wire in good condition?
YES: Go to Step 12.
NO: Repair or replace it. Then go to Step 16.
STEP 12. Check for exhaust leaks.
Q: Are there any abnormalities?
YES: Repair it. Then go to Step 16.
NO: Go to Step 13.
STEP 13. Check for intake system vacuum leak.
Q: Are there any abnormalities?
YES: Repair it. Then go to Step 16.
NO: Go to Step 14.
STEP 14. Check for entry of foreign matter (water, kerosene, etc.) into fuel.
Q: Are there any abnormalities?
YES: Replace the fuel. Then go to Step 16.
NO: Go to Step 15.
STEP 15. Replace the right bank injector.
1. Replace the right bank injector.
2. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 22. OBD-II Drive Cycle
3. Check the diagnostic trouble code (DTC).
Q: Is DTC P0171 set?
YES: Replace the ECM. When the ECM is replaced, register the ID code. Refer to ID Code Registration Judgment Table
NO: The inspection is complete.
STEP 16. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 22. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0171 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.