Inspection Procedure 22
COMMENT- Abnormal air/fuel ratio is suspected.
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of air/fuel ratio control system.
- Deteriorated catalyst.
DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
STEP 1. Using scan tool MB991502, read the diagnostic trouble code (DTC).
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to ON" position.
3. Read the DTC.
If DTC is not output, go to Step 2.
If DTC is output, refer to Diagnostic Trouble Code Chart.
STEP 2. Check the ignition timing.
Refer to On-vehicle Service-Ignition Timing Check.
If within specifications, go to Step 3.
If not within specifications, check that the crankshaft position sensor and timing belt cover are in the correct position. Then confirm that the malfunction symptom is eliminated.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
STEP 3. Using scan tool MB991502, check data list.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to "ON" position.
3. Check the following items in the data list.
Refer to Data List Reference Table.
a. Item 21: Engine Coolant Temperature Sensor.
b. Item 13: Intake Air Temperature Sensor.
c. Item 25: Barometric pressure Sensor.
d. Item 59: Heated Oxygen Sensor (rear)
e. Item 11: Heated Oxygen Sensor (front)
f. Item 69: Left Bank Heated Oxygen Sensor (rear)
g. Item 39: Left Bank Heated Oxygen Sensor (front)
If the checks above meet the specifications, go to Step 4.
If the checks above do not meet the specifications, repair or replace. Then confirm that the malfunction symptom is eliminated.
STEP 4. Using scan tool MB991502, check data list.
1. Check the following items of the data list. Refer to Data List Reference Table.
a. Item 11: Heated Oxygen Sensor (front)
b. Item 39: Left Bank Heated Oxygen Sensor (front)
- Voltage should fluctuate between 0 - 0.4 volts and 0.6 - 1.0 volts while idling after the engine has been warmed.
If the voltage does not fluctuate, go to Step 5.
If the voltage fluctuates, replace the heated oxygen sensor (front). Then confirm that the malfunction symptom is eliminated.
If not resolved, go to Step 6.
STEP 5. Check the fuel pressure.
Refer to Fuel Pressure Test.
If correct, go to Step 6.
If incorrect, repair or replace. Then confirm that the malfunction symptom is eliminated.
STEP 6. Check the following items.
1. Check the following items, and repair or replace the defective items.
a. Check the injectors for fuel leakage.
b. Check the ignition coil, spark plugs, spark plug cables.
c. Check compression pressure.
d. Check the positive crank case ventilation system.
e. Check the evaporative emission control system.
f. Check the EGR system.
2. Then check the malfunction symptom.
If the malfunction symptom is eliminated, the check is completed.
If the malfunction symptom is not eliminated, replace the catalytic converter. Then confirm that the malfunction symptom is eliminated.