Inspection Procedure 22

INSPECTION PROCEDURE 22
Too high CO and HC concentration when idling

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




STEP 1. Using scan tool MB991502, read the diagnostic trouble code (DTC).

CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.

If DTC is not output, go to Step 2.
If DTC is output, refer to Inspection Chart for Diagnostic Trouble Code.

STEP 2. Check the ignition timing.
Refer to On-vehicle Service.
If within specifications, go to Step 3.
If not within specifications, check and repair the crankshaft position sensor check that the timing belt cover is in the correct position. Then confirm that the malfunction symptom is eliminated.




STEP 3. Using scan tool MB991502, check data list.

CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.

(1) 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).
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 item 11: Heated Oxygen Sensor (front).

CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.

- 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 operation sound.
b. Check the injectors for fuel leakage.
c. Check the ignition coil, spark plugs, spark plug cables.
d. Check compression.
e. Check the positive crankcase ventilation system.
f. Check the evaporative emission control system.
g. Check the EGR system.
(2) Then check the malfunction symptom.
If the malfunction symptom is eliminated, the check is completed.
If the malfunction symptom has not been resolved, replace the catalytic converter. Then confirm that the malfunction symptom is eliminated,