P0173
Fuel Trim Circuit
CIRCUIT OPERATION
- The injector power is supplied from the MFI relay (terminal 1).
- The ECM
TECHNICAL DESCRIPTION
- If a malfunction occurs in the fuel system, the fuel trim value becomes too large or too small.
- The ECM
DTC SET CONDITIONS
Check Area
- Under the closed loop air/fuel ratio control.
- Intake air temperature is higher than -10 °C (14 °F).
- Engine coolant temperature is higher than -10 °C (14 °F).
- Barometric pressure is higher than 76 kPa (11 psi).
- Volume airflow sensor output frequency is 113 Hz or more.
Judgment Criteria
- Long term fuel trim has continued to be higher than +12.5 percent or lower than -12.5 percent for 10 seconds.
- Short term fuel trim has continued to be higher than +12.1 percent or lower than -12.1 percent for 10 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.
- Exhaust leak.
- Use of incorrect fuel.
- ECM failed
- PCM failed .
DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 1. Using scan tool MB991502, check data list item 13: Intake Air Temperature Sensor.
- The intake air temperature and temperature displayed on the scan tool should approximately match.
If they match, go to Step 2.
If they do not match, refer to DTC P0110 - Intake Air Temperature Circuit Malfunction.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 2. Using scan tool MB991502, check data list item 21: Engine Coolant Temperature Sensor.
- The engine coolant temperature and temperature displayed on the scan tool should approximately match.
If they match, go to Step 3.
If they do not match, refer DTC P0115 - Engine Coolant Temperature Circuit Malfunction.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 3. Using scan tool MB991502, check data list item 25: Barometric Pressure Sensor.
- At altitude 0 m (0 foot), 101 kPa.
- At altitude 600 m (1,969 foot), 95 kPa.
- At altitude 1,200 m (3,937 foot), 88 kPa.
- At altitude 1,800 m (5,906 foot), 81 kPa.
If within specifications, go to Step 4.
If not within specifications, refer to DTC P0105 - Barometric Pressure Circuit Malfunction.
STEP 4. Check the injector (Number 2, 4, 6).
1. Disconnect the injector connector.
2. Measure the resistance between injector side connector terminals 1 and 2.
Standard value: 13 - 16 Ohm [at 20 °C (68 °F)]
If within specifications, go to Step 5.
If not within specifications, replace the faulty injector. Then go to Step 14.
STEP 5. Check the harness wire between the injector connectors A-70, A-71, A-72 and the ECM connector C-50
NOTE: After inspecting the intermediate connector A-04, inspect the wire. If the intermediate connector A-04 is damaged, repair or replace it. Then go to Step 14.
If the wires between the injector connectors A- 70, A-71, A-72 and the ECM connector C-50
If the wires between the injector connectors A-70, A-71, A-72 and the ECM connector C-50
STEP 6. Check for damage of the harness connectors A-70, A-71, A-72 at the injector and the harness connector C-50 at the ECM
If harness connectors A-70, A-71, A-72 and C-50
If harness connectors A-70, A-71, A-72 and C-50
STEP 7. Check the fuel pressure.
Refer to Fuel Pressure Test.
If correct, go to Step 8.
If incorrect, repair or replace it. Then go to Step 14.
To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 8. Using scan tool MB991502, check data list item 81: Long-Term Fuel Trim.
If the fuel trim is more than zero, go to STEP 9. If the fuel trim is less than zero, go to Step 12.
STEP 9. Check the air flow into the intake system.
If correct, go to Step 10.
If incorrect, repair or replace. Then go to Step 14.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 10. Using scan tool MB991502, check data list item 12: Volume Air Flow Sensor.
- 18 and 44 Hz <3.5L Engine> (between 3.7 and 7.6 g/s).
- 58 and 98 Hz <3.5L Engine> (between 11.9 and 17.9 g/s).
If within specifications, go to Step 11.
If not within specifications, replace the volume air flow sensor. Then go to Step 14.
STEP 11. Check the following items.
1. Check the following items and repair or replace as needed.
a. Check for injector (Number 2, 4, 6) clogging.
b. Check for fuel filter and fuel line clogging.
c. Check fuel pump (insufficient delivery amount).
d. Check for exhaust leaks (left bank heated oxygen sensor installation section, cracks in exhaust manifold, cracks in front pipe, etc.)
e. Check for entry of foreign matter (water, kerosene, etc.) into fuel.
If malfunctioning, repair or replace.
If not malfunctioning, replace the ECM
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 12. Using scan tool MB991502, check data list item 12: Volume Air Flow Sensor.
- 18 and 44 Hz <3.5L Engine> (between 3.7 and 7.6 g/s).
- 58 and 98 Hz <3.5L Engine> (between 11.9 and 17.9 g/s).
If within specifications, go to Step 13.
If not within specifications, replace the volume air flow sensor. Then go to Step 14.
STEP 13. Check the following items.
1. Inspect the following items, and repair or replace as needed.
a. Check the injector (Number 2, 4, 6) fuel leakage.
b. Check for entry of foreign matter (water, kerosene, etc.) into fuel.
If incorrect, repair or replace it.
If correct, replace the ECM
STEP 14. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. OBD-II Drive Cycle Pattern Lists
2. Read the diagnostic trouble code, and confirm that a diagnostic trouble code is not being output.