P0171
System too Lean (bank 1) Circuit- Refer to DTC P0201, P0203, P0205 - Injector Circuit.
CIRCUIT OPERATION
- Refer to DTC P0201, P0203, P0205 - Injector Circuit.
TECHNICAL DESCRIPTION
- If a malfunction occurs in the fuel system, the fuel trim value becomes too large.
- The ECM
DTC SET CONDITIONS
Check Area
- Engine coolant temperature is lower than approximately 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 77 °C (171 °F).
- Volume air flow sensor output frequency is 75 Hz or more.
Judgment 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 Area
- Engine coolant temperature is lower than approximately 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 77 °C (171 °F).
- Volume air flow sensor output frequency is 75 Hz or less.
Judgment 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 +12.5 percent for 5 seconds.
Check Area
- Engine coolant temperature is higher than approximately 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 77 °C (171 °F).
- Volume air flow sensor output frequency is 75 Hz or more.
Judgment 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 +17.6 percent for 5 seconds.
Check Area
- Engine coolant temperature is higher than approximately 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 77 °C (171 °F).
- Volume air flow sensor output frequency is 75 Hz or less.
Judgment 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 +22.3 percent for 5 seconds.
Check Area
- Engine coolant temperature is higher than 77 °C (171 °F).
- Under the closed loop air/fuel ratio control.
Judgment Criteria
- Long-term fuel trim has continued to be +12.5 percent for 5 seconds.
or
- Short-term fuel trim has continued to be +25.0 percent for 5 seconds.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Volume air flow sensor failed.
- Injector (Number 1, 3, 5) failed.
- Incorrect fuel pressure.
- Air drawn in from gaps in gasket, seals, etc.
- Right bank heated oxygen sensor failed.
- Engine coolant temperature sensor failed.
- Intake air temperature sensor failed.
- Barometric pressure sensor failed.
- Use of incorrect or contaminated fuel.
- ECU failed.
- PCM failed.
DIAGNOSIS
Required Special Tool:
- MB991502: Scan Tool (MUT-II)
STEP 1. Check the exhaust leaks.
Q: Are there any abnormalities?
YES: Go to Step 2.
NO: Repair it. Then go to Step 16.
STEP 2. Check the intake system vacuum leak.
Q: Are there any abnormalities?
YES: Go to Step 3.
NO: Repair it. Then go to Step 16.
STEP 3. Using scan tool MB991502, check data list item 12: Volume Air Flow Sensor.
CAUTION
To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 12, Volume Air Flow Sensor.
4. Warm up the engine to normal operating temperature: 80 °C to 95 °C (176 °F to 203 °F).
- When idling, between 17 and 46 Hz (between 2.2 and 5.7 gm/s).
- When 2,500 rpm, between 63 and 103 Hz (between 9.0 and 14.7 gm/s).
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 4.
NO: Refer to DTC P0101 - Volume Air Flow Circuit Range/Performance Problem, DTC P0102 - Volume Air Flow Circuit Low Input.
STEP 4. Using scan tool MB991502, check data list item 13: Intake Air Temperature Sensor.
1. Turn the ignition switch to the "ON" position.
2. Set scan tool MB991502 to the data reading mode for item 13, 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 5.
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 5. Using scan tool MB991502, check data list item 21: Engine Coolant Temperature Sensor.
1. Turn the ignition switch to the "ON' position.
2. Set scan tool MB991502 to the data reading mode for item 21, 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 6.
NO: Refer to DTC P0116 - Engine Coolant Temperature Circuit Range/Performance Problem, DTC P0117 - Engine Coolant Temperature Circuit Low Input, DTC P0118 - Engine Coolant Temperature Circuit High Input.
STEP 6. Using scan tool MB991502, check data list item 25: Barometric Pressure Sensor.
1. Turn the ignition switch to the "ON" position.
2. Set scan tool MB991502 to the data reading mode for item 25, Barometric 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).
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 7.
NO: Refer to DTC P0106 - Barometric Pressure Circuit Range/Performance Problem, DTC P0107 - Barometric pressure Circuit Low Input, DTCP0108 - Barometric Pressure Circuit High Input.
STEP 7. Check connector B-118 at injector intermediate connector for damage.
Q: Is the connector in good condition?
YES: Go to Step 8.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 16.
STEP 8. Measure the right bank injector resistance at intermediate connector B-118.
1. Disconnect the injector intermediate connector B-118.
2. Measure the resistance between each male connector side connector terminal.
a. Measure the resistance between terminal No.1 and No. 2 when measuring No.1 cylinder.
b. Measure the resistance between terminal No.1 and No. 3 when measuring No.3 cylinder.
c. Measure the resistance between terminal No.1 and No. 4 when measuring No.5 cylinder.
- Resistance should be between 13 and 16 ohms @ 20 °C (68 °F).
Q: Is the measured resistance between 13 and 16 ohms @ 20 °C (68 °F)?
YES: Go to Step 11.
NO: Go to Step 9.
STEP 9. Check connectors B-01, B-05, B-26 at right bank injector for damage.
1. Remove the intake manifold.
2. Check the injector connector, which deviates from the standard value at Step 8.
Q: Is the connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 16.
STEP 10. Check the right bank injector.
1. Disconnect the right bank injector connector, which deviates from the standard value at Step 8.
2. Measure the resistance between injector side connector terminals No.1 and No.2.
Standard value: 13 - 16 ohms @ 20 °C (68 °F)
Q: Is the resistance between 13 and 16 ohms @ 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.
Connectors:
STEP 11. Check connector C-111 at ECM
Q: Is the connector in good condition?
YES: Go to Step 12.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 16.
Connectors:
STEP 12. Check for harness damage between right bank injector connector and ECM connector
a. Check the harness wire between injector connector B-01 (terminal No.2) and ECM connector C-111 (terminal No.1)
b. Check the harness wire between injector connector B-05 (terminal No.2) and ECM connector C-111 (terminal No. 24)
c. Check the harness wire between injector connector B-26 (terminal No.2) and ECM connector C-111 (terminal No. 10)
Q: Is the harness wire in good condition?
YES: Go to Step 13.
NO: Repair it. Then go to Step 16.
STEP 13. Check the fuel pressure. Refer to On-vehicle Service - Fuel Pressure Test.
Q: Is the fuel pressure normal?
YES: Go to Step 14.
NO: Repair or replace it. Then go to Step 16.
STEP 14. Check for entry of foreign matter (water, kerosene, etc.) into fuel.
Q: Are there any abnormalities?
YES: Go to Step 15.
NO: Replace the fuel. Then go to Step 16.
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 Trouble Code Diagnosis - OBD-II Drive Cycle - Procedure 2 - Fuel Trim Monitor.
3. Check the diagnostic trouble code (DTC).
Q: Is DTC P0171 set?
YES: Replace the ECM or PCM. Then go to Step 16.
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 Trouble Code Diagnosis - OBD-II Drive Cycle - Procedure 2 - Fuel Trim Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0171 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.