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Inspection Procedure 7: Too high CO and HC concentration
 
 
 
 
COMMENT
Abnormal air-fuel ratio is suspected.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this case:)
  • Fuel pump system failed.
  • Linear air-fuel ratio sensor failed.
  • Heated oxygen sensor (rear) failed.
  • Ignition system failed.
  • Poor compression.
  • EGR system failed.
  • Improper operation of the PCV valve.
  • Evaporative emission system failed.
  • ECM failed.
 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
1.STEP 1. Check the EGR valve (stepper motor).
Check the EGR valve operation sound [Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Exhaust Gas Recirculation (EGR) System EXHAUST GAS RECIRCULATION (EGR) VALVE (STEPPER MOTOR) CHECK].
Q: Is the check result normal?
Check the EGR valve itself [Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Exhaust Gas Recirculation (EGR) System EXHAUST GAS RECIRCULATION (EGR) VALVE (STEPPER MOTOR) CHECK].
 
2.STEP 2. Using scan tool (M.U.T.-III SE), read the DTC.
Use scan tool (M.U.T.-III SE) to check and see if a DTC is set in the ECM (Refer to HOW TO READ AND ERASE DIAGNOSTIC TROUBLE CODES).
Q: Is any DTC set?
Perform troubleshooting for the set DTC (Refer to DIAGNOSTIC TROUBLE CODE CHART).
 
3.STEP 3. Check the ignition timing.
Check the ignition timing (Refer to ENGINE, Engine Mechanical – On-vehicle Service IGNITION TIMING CHECK ).
Q: Is the ignition timing normal?
Align the timing marks (Refer to ENGINE, Engine Overhaul – Timing Chain TIMING CHAIN REMOVAL AND INSTALLATION ).
 
4.STEP 4. Using scan tool (M.U.T.-III SE), check the data list.
Use scan tool (M.U.T.-III SE) to check the data list (Refer to DATA LIST REFERENCE TABLE).
  • Item number 50: Air Temperature Sensor
  • Item number 60: Coolant (Water) Temperature Sensor
  • Item number A1501: Oxygen sensor(bank1 sensor2)
  • Item number A3417: LAFS (Bank1 Sensor1)
Q: Are the check result normal?
Perform the DTC classified check procedure for the sensor that has shown an abnormal data value (Refer to DIAGNOSTIC TROUBLE CODE CHART).
 
5.STEP 5. Check the fuel pressure.
Fuel pressure measurement (Refer to FUEL PRESSURE TEST ).
Q: Is the check result normal?
Repair it.
 
6.STEP 6. Check the spark plug.
Check the number 1 cylinder spark plug, number 2 cylinder spark plug, number 3 cylinder spark plug and number 4 cylinder spark plug itself (Refer to ENGINE , Engine Electrical – On-vehicle Service SPARK PLUG CHECK AND CLEANING).
Q: Are the check result normal?
Replace the faulty spark plug (Refer to ENGINE , Engine Electrical – Ignition Coil IGNITION COIL REMOVAL AND INSTALLATION).
 
7.STEP 7. Check the ignition coil.
Check the number 1 cylinder ignition coil, number 2 cylinder ignition coil, number 3 cylinder ignition coil and number 4 cylinder ignition coil itself (Refer to ENGINE , Engine Electrical – On-vehicle Service IGNITION COIL CHECK).
Q: Are the check result normal?
Replace the faulty ignition coil (Refer to ENGINE , Engine Electrical – Ignition Coil IGNITION COIL REMOVAL AND INSTALLATION).
 
8.STEP 8. Check the compression pressure.
Check the compression pressure (Refer to ENGINE, Engine Mechanical – On-vehicle Service COMPRESSION PRESSURE CHECK ).
Q: Is the check result normal?
Repair it.
 
9.STEP 9. Check the positive crankcase ventilation valve.
Check the positive crankcase ventilation valve itself (Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Positive Crankcase Ventilation System POSITIVE CRANKCASE VENTILATION (PCV) VALVE CHECK).
Q: Is the check result normal?
Replace the positive crankcase ventilation valve (Refer to ENGINE, Engine Overhaul – Oil Pan and Timing Chain Case OIL PAN AND TIMING CHAIN CASE REMOVAL AND INSTALLATION ).
 
10.STEP 10. Check the purge control system.
Check the purge control system (Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Evaporative Emission System – Purge Control System Check PURGE CONTROL SYSTEM CHECK (PURGE FLOW CHECK)).
Q: Is the check result normal?
Repair it.
 
11.STEP 11. Check the fuel injector.
Check the number 1 cylinder fuel injector, number 2 cylinder fuel injector, number 3 cylinder fuel injector and number 4 cylinder fuel injector itself (Refer to FUEL INJECTOR CHECK).
Q: Are the check result normal?
Replace the faulty fuel injector (Refer to FUEL INJECTOR REMOVAL AND INSTALLATION).
 
12.STEP 12. Check for air intake or exhaust leaks from the EGR valve, EGR cooler, EGR pipe and EGR intake pipe.
Check the EGR valve, EGR cooler, EGR pipe and EGR intake pipe [Refer to ENGINE, Engine, Motor and Emission Control – Emission Control, Exhaust Gas Recirculation (EGR) System EGR PIPING DAMAGE AND INSTALLATION CONDITION CHECK].
Q: Is the check result normal?
Repair the EGR valve, the EGR cooler, the EGR pipe or the EGR intake pipe.
 
13.STEP 13. Check the EGR valve contamination, the EGR cooler contamination, the EGR pipe contamination and the EGR intake pipe contamination.
Check the EGR valve, EGR cooler, EGR pipe and EGR intake pipe for stuck closed.
Q: Is the check result normal?
Repair the EGR valve, the EGR cooler, the EGR pipe or the EGR intake pipe.
 
14.STEP 14. Check the malfunction symptoms.
Q: Does the malfunction symptom persist?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
Intermittent malfunction (Refer to GENERAL INFORMATION, General Information – How to Use Troubleshooting/Inspection Service Points HOW TO COPE WITH INTERMITTENT MALFUNCTIONS).