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Excessive Exhaust Emissions or Odors: Troubleshooting

TROUBLESHOOTING CHART

Step Action Value (s) Yes No
1 Were the Important Preliminary Checks performed? - Go to Step 2 Go to "IMPORTANT PRELIMINARY CHECKS " in
2
  1. Run the engine until it reaches operating temperature.
  2. Perform an emission test.

Does the vehicle pass the emission test?		 - System OK Go to Step 3
3
  1. Connect the scan tool to the Data Link Connector (DLC).
  2. Road test the vehicle.
  3. Monitor the long term fuel trim memory.

Is the long term fuel trim memory within the value specified?		 -20 - 25% Go to Step 6 Go to Step 4
4 Is the long term fuel trim memory below the value specified? -20% Go to DTC P0172: Fuel Trim System Rich Go to Step 5
5 Is the long term fuel trim memory above the value specified? 25% Go to DTC P0171: Fuel Trim System Lean -
6
  1. Check for a properly installed fuel cap.
  2. Check the fuel system pressure.
  3. Perform an FUEL INJECTOR BALANCE TEST .

Is the problem found?		 - Go to Step 7 Go to Step 8
7
  1. Repair or replace any fuel system components as needed.
  2. Perform an emission test.

Does the vehicle pass the emission test?		 - System OK -
8
  1. Check the ignition system for proper operation.
  2. Inspect the spark plugs for excessive wear, insulation cracks, improper gap, or heavy deposits.
  3. Check the ignition wires for cracking, hardness, or improper connections.

Is the problem found?		 - Go to Step 9 Go to Step 10
9
  1. Repair or replace any ignition system components as needed.
  2. Perform an emission test.

Does the vehicle pass the emission test?		 - System OK -
10
  1. Inspect for vacuum leaks.
  2. Inspect the catalytic converter for contamination.
  3. Inspect for carbon buildup on the throttle body and the throttle plate and inside the engine. Remove with a top engine cleaner.
  4. Check the Exhaust Gas Recirculation (EGR) valve to make sure it opens.
  5. Check for proper Positive Crankcase Ventilation (PCV) operation.

Are all checks and needed repairs complete?		 - System OK -
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