P0174
System too Lean (bank 2) Circuit- Refer to DTC P0202, P0204, P0206 - Injector Circuit.
CIRCUIT OPERATION
- Refer to DTC P0202, P0204, P0206- 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 4emperature 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 2, 4, 6) failed.
- Incorrect fuel pressure.
- Air drawn in from gaps in gasket, seals, etc.
- Left 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 14.
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 14.
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, DTC P0108 - Barometric Pressure Circuit High Input.
STEP 7. Check connectors B-02, B-06, B-25 at left bank injector 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 14.
STEP 8. Check the left bank injector.
1. Disconnect the left bank injector connectors B-02, B-06, B-25.
2. Measure the resistance between each 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: Go to Step 9.
NO: Replace the faulty injector. Then go to Step 14.
Connectors:
STEP 9. Check connector C-111 at ECM
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 14.
Connectors:
STEP 10. Check for harness damage between left bank injector connector and ECM connector
a. Check the harness wire between injector connector B-02 (terminal No.2) and ECM connector C-111 (terminal No.9)
b. Check the harness wire between injector connector B-06 (terminal No.2) and ECM connector C-111 (terminal No.2)
c. Check the harness wire between injector connector B-25 (terminal No.2) and ECM connector C-111 (terminal No. 25)
Q: Is the harness wire in good condition?
YES: Go to Step 11.
NO: Repair it. Then go to Step 14.
STEP 11. Check the fuel pressure.
Refer to On-vehicle Service - Fuel Pressure Test P.14E-14.
Q: Is the fuel pressure normal?
YES: Go to Step 12.
NO: Repair or replace it. Then go to Step 14.
STEP 12. Check for entry of foreign matter (water, kerosene, etc.) into fuel.
Q: Are there any abnormalities?
YES: Go to Step 13.
NO: Replace the fuel. Then go to Step 14.
STEP 13. Replace the left bank injector.
1. Replace the left 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 P0174 set?
YES: Replace the ECM or PCM. Then go to Step 14.
NO: The inspection is complete.
STEP 14. 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 P0174 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.