P0173
CIRCUIT OPERATION- The injector power is supplied from the MFI relay (terminal 1).
- The PCM controls the injector by turning the power transistor in the PCM "ON" and "OFF."
TECHNICAL DESCRIPTION
- If a malfunction occurs in the fuel system, the fuel trim value becomes too large or too small.
- The PCM checks whether the fuel trim value is within a specified range.
DTC SET CONDITIONS
Check Area
- Under the closed loop air/fuel ratio control.
- Engine coolant temperature is higher than -10° C (14° F)
- Intake air temperature is higher than -10° C (14° F).
- Barometric pressure sensor is higher than 76 kPa (11 psi).
- Volume air flow sensor output frequency is 100 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 +7.4 percent or lower than -7.4 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.
- PCM failed.
WIRING DIAGRAM
CONNECTORS
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 to 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 each injector side connector terminals 1 and 2.
Standard value: 13 - 16 ohms [at 20° C (68° F)]
If within specifications, go to Step 5.
If not within specifications, replace the injector. Then go to Step 14.
STEP 5. Check the harness wire between the injector connectors B-17, B-21, B-30 and the PCM connector C-39.
NOTE: After inspecting the intermediate connector B-26, inspect the wire. If the Intermediate connector B-26 is damaged, repair or replace it. Refer to Harness Connector Inspection >. Then go to Step 14.
If the wires between the injector connectors B-17, B-21, B-30 and the PCM connector C-39 are not damaged, go to Step 6.
If the wires between the injector connectors B-17, B-21, B-30 and the PCM connector C-39 are damaged, repair them. Then go to Step 14
STEP 6. Check for damage of the harness connectors B-17, B-21, B-30 at the injector and the harness connector C-39 at the PCM.
If harness connectors B-17, B-21, B-30 and C-39 are in good condition, go to Step 7.
If harness connectors B-17, B-21, B-30 and C-39 are damaged, repair or replace them. Refer to Harness Connector Inspection >. Then go to Step 14.
STEP 7. Check the fuel pressure.
Refer Fuel Pressure Test.
If correct, go to Step 8.
If incorrect, repair or replace it. 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 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.
- When idling, between 17 and 46 Hz (between 2.2 and 5.7 g/s).
- When 2,500 r/min, between 63 and 103 Hz (between 9.0 and 14.7 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 PCM.
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 12. Using scan tool MB991502, check data list item 12: Volume Air Flow Sensor.
- When idle, between 17 and 46 Hz (between 2.2 and 5.7 g/s).
- When 2,500 r/min, between 63 and 103 Hz (between 9.0 and 14.7 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 PCM.
Then go to Step 14.
STEP 14. Test the OBD-II drive cycle
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 2 - Fuel Trim Monitor.
2. Read the diagnostic trouble code, and confirm that a diagnostic trouble code is not being output.