California

Excessive Time to Enter Closed Loop Fuel Control Circuit

CIRCUIT OPERATION

Right Bank Heated Oxygen Sensor (front) Circuit:

Right Bank Heated Oxygen Sensor (front) Circuit
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal 72) or PCM (terminal 72) from the output terminal (terminal 4) of the right bank heated oxygen sensor (front).
- Terminal 2 of the right bank heated oxygen sensor (front) is grounded with ECM (terminal 49) or PCM (terminal 57) .

Left Bank Heated Oxygen Sensor (front ) Circuit:

Left Bank Heated Oxygen Sensor (front) Circuit
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal 71) or PCM (terminal 71) from the output terminal (terminal 4) of the left bank heated oxygen sensor (front).
- Terminal 2 of the left bank heated oxygen sensor (front) is grounded with ECM (terminal 49) or PCM (terminal 57) .

Injector Circuit:

Connectors: A-21X, B-01, B-02, B-05, B-06, B-25, B-26, B-48, C-51 <M/T>, C-52 <A/T>:

Injector Circuit
- The injector power is supplied from the MFI relay (terminal 1).
- The ECM or PCM controls the injector by turning the power transistor in the ECM or PCM ON" and "OFF."

TECHNICAL DESCRIPTION
- The MFI system reduces exhaust emissions by means of closed loop fuel control.
- The ECM or PCM checks the time taken until closed loop fuel control commences.

DTC SET CONDITIONS

Check Conditions
- Thirty seconds or more have passed since the starting sequence was completed.
- Engine coolant temperature is higher than 81°C (178°F).
- Engine speed is at between about 1,800 and 3,500 r/min.
- Volumetric efficiency is at between 16 and 62 percent.
- The engine is running in the air/fuel ratio feedback zone.
- Monitoring time: 30 seconds.

Judgment Criteria
- Multiport fuel injection system does not enter the closed loop control within about 30 seconds.
- Only one monitor during one drive cycle

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Heated oxygen sensor failed.
- Injector failed.
- Fuel pressure regulator failed.
- Fuel pump failed.
- Fuel filter is clogged.
- Intake system vacuum leak.
- Exhaust leak.
- ECM failed.
- PCM failed.

DIAGNOSIS
Required Special Tool:
MB998464: Test Harness

STEP 1. Check for exhaust leaks.
If no leaks are found, go to Step 2.
If leaks are found, repair them. Then go to Step 15.

STEP 2. Check for intake system vacuum leaks.
If no leaks are found, go to Step 3.
If leaks are found, repair or replace them. Then go to Step 15.

STEP 3. Check the right bank and left bank heated oxygen sensor (front).
1. Disconnect the heated oxygen sensor (front) connector B-27 or B-24 and connect special tool MB998464 to the connector on the heated oxygen sensor (front) side.
2. Warm up the engine until engine coolant is 80°C (176°F) or higher.

CAUTION: Be very careful when connecting the jumper wires. Incorrect connection can damage the heated oxygen sensor (front).

3. Use the jumper wires to connect terminal 1 of the heated oxygen sensor (front) connector to the positive battery terminal and terminal 3 to the battery negative terminal.
4. Connect a digital voltmeter between terminal 2 and terminal 4.
5. While repeatedly revving the engine, measure the heated oxygen sensor (front) output voltage.

Standard value: 0.6 - 1.0 V

If within specifications, go to Step 4.

If not within specifications, replace the heated oxygen sensor (front). Then go to Step 15.

STEP 4. Check the harness connector B-27 or B-24 at the heated oxygen sensor (front) for damage.
If harness connector B-27 or B-24 is in good condition, go to Step 5.

If the harness connector B-27 or B-24 is damaged, repair or replace it.

Refer to Harness Connector Inspection. Then go to Step 15.

STEP 5. Check the left bank injector.

1. Disconnect the left bank 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 6.

If not within specifications, replace the injector. Then go to Step 15.

STEP 6. Check injector intermediate connector B-48 at the right bank injector.
1. Disconnect the injector intermediate harness connector.

2. Measure the resistance between injector side connector terminals 1 and 2 (No.1 injector), 1 and 3 (No.3 injector), 1 and 4 (No. 5 injector).

Standard value: 13 - 16 ohms [at 20°C (68°F)]

If within specifications, go to Step 9.
If not within specifications, go to Step 7.

STEP 7. Check the right bank injector.
1. Remove the intake manifold.
2. Disconnect the injector connector deviated from the standard value listed in Step 6.

3. Measure the resistance between injector side connector terminals 1 and 2.

Standard value: 13 - 16 ohms [at 20°C (68°F)]

If within specifications, go to Step 8.
If not within specifications, replace the injector. Then go to Step 15.

STEP 8. Check harness connector B-01 or B-05 or B-26 at the right bank injector for damage.
Check the injector connector, which deviates from the standard value at Step 6.

If harness connector is in good condition, repair the harness wire between the injector connector and injector intermediate harness connector. Then go to Step 15.

If harness connector is damaged, repair or replace it.

Refer to Harness Connector Inspection. Then go to Step 15.

STEP 9. Check injector intermediate connector B-48 for damage.
If harness connector B-48 is in good condition, go to Step 10.

If harness connector B-48 is damaged, repair or replace it.
Refer to Harness Connector Inspection. Then go to Step 15.

STEP 10. Check harness connector B-02, B-06, B-25 at the left bank injector for damage.
If harness connectors B-02, B-06, B-25 are in good condition, go to Step 11.

If harness connectors B-02, B-06, B-25 are damaged, repair
or replace it.
Refer to Harness Connector Inspection. Then go to Step 15.

STEP 11. Check the harness connectors C-51, C-58, C-62 at the ECM or harness connector C-52, C-55, C-59 at the PCM for damage.
If harness connectors C-51, C-58, C-62 or C-52, C-55, C-59 are in good condition, go to Step 12.

If harness connectors C-51, C-58, C-62 or C-52, C-55, C-59 are damaged, repair or replace it.
Refer to Harness Connector Inspection. Then go to Step 15.

STEP 12. Check the harness wire between the heated oxygen sensor (front) connector B-27 or B-24 and the ECM connector C-58, C-62 PCM connectors C-55, C-59 .
If the wire between the heated oxygen sensor (front) connector
B-27 or B-24 and the ECM connector C-58, C-62 or PCM connectors C-55, C-59 are not damaged, go to Step 13.

If the wire between the heated oxygen sensor (front) connector
B-27 or B-24 and the ECM connector C-58, C-62 or PCM connectors C-55, C-59 are damaged, repair it. Then go to Step 15.

STEP 13. Check the harness wire between injector connectors B-01, B-02, B-05, B-06, B-25, B-26 and the ECM connector C-51 or PCM connector C-52.
If the wire between injector connectors B-01, B-02, B-05, B-06 B-25, B-26 and the ECM connector C-51 or PCM connector C-52 are not damaged, go to Step 14.

If the wire between injector connectors B-01, B-02, B-05, B-05, B-25, B-26 and the ECM connector C-51 or PCM connector C-52 are damaged, repair it. Then go to Step 15.

STEP 14. Check the fuel pressure.
Refer to Fuel Pressure Test. If correct, replace the ECM or PCM. Then go to Step 15.

If incorrect, repair or replace it. Then go to Step 15.

STEP 15. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
2. Read the diagnostic trouble code, and confirm that a diagnostic trouble code P0125 does not reset.