Inspection Procedure 23
COMMENT- The test is failed when the air/fuel ratio is not controlled to the ideal air/fuel ratio. This occurs due to the feedback control by heated oxygen sensor signals, insufficient EGR flow rate, or deteriorated catalyst.
NOTE: If the three-way catalyst temperature is low when checking the exhaust gas, the three-way catalyst cannot sufficiently clean the emissions. Warm up the engine sufficiently before checking the exhaust, and check immediately
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of air/fuel ratio control system.
- Malfunction of the EGR system.
- Deteriorated catalyst.
DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)
STEP 1. Check the exhaust gas with the engine at normal operating temperature.
1. Check that the engine is at normal operating temperature.
If warmed up, go to Step 2.
If not warmed up, warm up the engine completely before checking the exhaust gas.
STEP 2. Check the following items.
1. Check the following items.
a. Check all vacuum hoses and connectors.
b. Check electrical wires and connectors for obvious problems.
c. Check the exhaust system for missing or damaged parts.
If not malfunctioning, go to Step 3.
If malfunctioning, repair or replace. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check the drive-ability.
1. Check if the malfunction symptom described on the symptom chart is occurring.
If normal, go to Step 4.
If not normal, refer to Symptom Chart.
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 4. 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 5.
If DTC is output, refer to Diagnostic Trouble Code Chart.
STEP 5. Check the ignition timing.
Refer to On-vehicle Service - Ignition Timing Check.
If within specifications, go to Step 6.
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 6. 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)
Right Bank Heated Oxygen Sensor (rear)
e. Item 69: Left Bank Heated Oxygen Sensor (rear)
If the checks above meet the specifications, go to Step 7.
If the checks above do not meet the specifications, repair or replace. Then confirm that the malfunction symptom is eliminated.
STEP 7. Using scan tool MB991502, check data list item 11: Heated oxygen sensor (front)
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 11, Heated Oxygen Sensor (front)
- Warm up the engine. When the engine is decelerated suddenly from 4000 r/min, the output voltage should increase from 200 mV or less to 600 - 1000 mV in a few seconds.
If within specifications, go to Step 8
If not within specifications, refer to DTC P0130 - Oxygen Sensor Circuit Malfunction (sensor 1)
STEP 8. Using scan tool MB991502, check data list item 11: Heated oxygen sensor (front)
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 11, 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 fluctuates, go to Step 9.
If the voltage does not fluctuate, go to Step 18.
STEP 9. Check the EGR system.
Refer to Emission Control System - EGR System Check.
If correct, go to Step 10.
If incorrect, repair or replace. Then confirm that the malfunction symptom is eliminated.
STEP 10. Check the idle mixture.
Refer to On-vehicle Service - Idle Mixture Check.
Standard value: CD contents 0.5% or less.
If within specifications, go to Step 19.
If not within specifications, replace the heated oxygen sensor (front). Then confirm that the malfunction symptom is eliminated.
STEP 11. Using scan tool MB991502, check data list item 39: Left Bank Heated oxygen sensor (front)
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 39, Left Bank Heated Oxygen Sensor (front)
If within specifications, go to Step 12.
If not within specifications, refer to DTC P0150 - Oxygen Sensor Circuit Malfunction (bank 2, sensor 1)
STEP 12. Using scan tool MB991502, check data list item 11: Right Bank Heated oxygen sensor (front)
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 11, Right Bank Heated Oxygen Sensor (front)
- Voltage should fluctuate between 0 - 0.4 volts and 0.6 - 1.0 volts while after the engine has been warmed.
If the voltage fluctuates, go to Step 13.
If the voltage does not fluctuate, go to Step 15.
STEP 13. Check the EGR system.
Refer to Emission Control System - EGR System Check.
If correct, go to Step 14.
If incorrect, repair or replace. Then confirm that the malfunction 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 14. Using scan tool MB991502, check data list item 59: Right Bank Heated oxygen sensor (rear)
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 59, Right Bank Heated Oxygen Sensor (rear)
- Average voltage should be 0.6 volts or less, when idling.
If within specifications, go to Step 19.
If not within specifications, replace the right bank heated oxygen sensor (front). Then confirm that the malfunction is eliminated.
STEP 15. Using scan tool MB991502, check data list item 39: Left Bank Heated oxygen sensor (front)
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 39, Left Bank Heated Oxygen Sensor (front)
- Warm up the engine. When the engine is decelerated suddenly from 4000 r/min, the output voltage should increase from 200 mV or less to 600 - 1000 mV in a few seconds.
If the voltage fluctuates, go to Step 16.
If the voltage does not fluctuate, got to Step 18.
STEP 16. Check the EGR system.
Refer to Emission Control System - EGR System Check.
If correct, go to Step 17.
If correct, repair or replace. Then confirm that the malfunction 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 17. Using scan tool MB991502, check data list item 69: Left Bank Heated oxygen sensor (rear)
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 69, Left Bank Heated Oxygen Sensor (rear)
- Average voltage should be 0.6 volts or less, when idling.
If within specifications, go to Step 19.
If not within specifications, replace the left bank heated oxygen sensor (front). Then confirm that the malfunction is eliminated.
STEP 18. Check the fuel pressure.
Refer to Fuel Pressure Test.
If correct, go to Step 19.
If incorrect, repair or replace. Then confirm that the malfunction symptom is eliminated.
STEP 19. 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 crankcase ventilation system.
e. Check the evaporative emission control 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.