Inspection Procedure 23
INSPECTION PROCEDURE 23: Transient, Mass Emission Tailpipe Test FailureCOMMENT
- 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 Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
STEP 1. Check the exhaust gas with the engine at normal operating temperature.
Q: After enough warm up, was the exhaust gas checked enough?
YES: Go to Step 2.
NO: Check it again after enough warm up.
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.
Q: Are they normal?
YES: Go to Step 3.
NO: Repair or replace it. 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.
Q: Is the drive-ability normal?
YES: Go to Step 4.
NO: Refer to, Trouble Symptom Chart. Symptom Chart
STEP 4. Using scan tool MB991958, read the diagnostic trouble code (DTC).
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Read the DTC.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC set?
YES: Refer to, Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO: Go to Step 5.
STEP 5. Check the ignition timing.
Refer to On-vehicle Service - Ignition Timing Check in Ignition Timing.
Q: Is the ignition timing normal?
YES: Go to Step 6.
NO: Check that the crankshaft position sensor and timing belt cover are in the correct position. Then confirm that the malfunction symptom is eliminated.
STEP 6. Using scan tool MB991958, check data list.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Check the following items in the data list. Refer to, Data List Reference Table. Data List Reference Table & Normal Scan Data Values
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).
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 7.
NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 7. Using scan tool MB991958, check data list item 11: heated oxygen sensor (front).
1. Start the engine and run at idle.
2. Set scan tool MB991958 to the data reading mode for item 11, Heated Oxygen Sensor (front).
- Warm up the engine. When the engine is decelerated suddenly from 4,000 r/min, the output voltage should increase from 200 mV or less to 600 - 1,000 mV in a few seconds.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 8.
NO: Refer to, DTC P0130 - Heated Oxygen Sensor Circuit (sensor 1) P0130, DTC P0131 - Heated Oxygen Sensor Low Voltage (sensor 1) P0131, DTC P0132 - Heated Oxygen Sensor Circuit High Voltage (sensor 1) P0132, DTC P0133 - Heated Oxygen Sensor Circuit Slow Response (sensor 1) P0133, DTC P0134 - Heated Oxygen Sensor Circuit No Activity Detected (sensor 1). P0134
STEP 8. Using scan tool MB991958, check data list item 11: Heated oxygen sensor (front).
1. Start the engine and run at idle.
2. Set scan tool MB991958 to the data reading mode for item 11, Heated Oxygen Sensor (front).
- Voltage should fluctuate between 0 - 0.4 volt and 0.6 - 1.0 volt while after the engine has been warmed.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 9.
NO: Go to Step 11.
STEP 9. Check the EGR system.
Refer to Emission Control Systems- EGR System Check in Emission Control Systems/Exhaust Gas Recirculation/Testing and Inspection.
Q: Is the EGR system normal?
YES: Go to Step 10.
NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 10. Using scan tool MB991958, check data list item 59: Heated oxygen sensor (rear).
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991958 to the data reading mode for item 59, Heated Oxygen Sensor (rear).
- Average voltage should measure 0.6 volts or less, when idling.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 12.
NO: Replace the heated oxygen sensor (front). Then confirm that the malfunction symptom is eliminated.
STEP 11. Check the fuel pressure.
Refer to On-vehicle Service Fuel Pressure Test. Testing and Inspection
Q: Is the fuel pressure normal?
YES: Go to Step 12.
NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 12. 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 and spark plug cables.
c. Check compression pressure.
d. Check the positive crankcase ventilation system.
e. Check the evaporative emission system.
2. Then check the malfunction symptom.
Q: Is the malfunction symptom is eliminated?
YES: The check is completed.
NO: Replace the catalytic converter. Then confirm that the malfunction symptom is eliminated.