Definition: Vehicle fails an emission test. Vehicle has excessive rotten egg smell. (Excessive odors do not necessarily indicate excessive emissions.)

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

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Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found, correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

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Go to Step 13

Go to Step 3

Was visual/physical check performed?

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Go to Step 4

Go to Important Preliminary Checks

1. Check for vacuum leaks. (Vacuum lines, Intake manifold, Throttle body etc.).
2. If a problem is found, repair as necessary.

Were any vacuum leaks located?

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Go to Step 13

Go to Step 5

Check the MAP sensor for proper operation. Refer to Manifold Absolute Pressure Sensor Output Diagnosis

Was a problem found?

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Go to Step 20

Go to Step 6

1. Check the fuel pressure. Perform the procedure in Fuel System Diagnosis
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 12

Go to Step 7

1. Check the injector connections.
2. If any of the injectors are connected to an incorrect cylinder, correct as necessary.

Was a problem found?

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Go to Step 12

Go to Step 8

1. Perform the Fuel Injector Solenoid Coil Test and Fuel Injector Balance Test .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 12

Go to Step 9

1. Refer to Engine Cooling for cooling system diagnosis.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 12

Go to Step 10

1. Check the EVAP canister for fuel loading.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 12

Go to Step 11

1. Remove the excessive carbon buildup with a top engine cleaner. Refer to the instructions on of the top engine cleaner can.
2. Perform the exhaust emission test.

Does the vehicle pass the test?

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System OK

Go to Step 13

Perform the exhaust emission test.

Does the vehicle pass the test?

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System OK

Go to Step 13

Does the exhaust emission test indicate excessive CO and HC levels or is the Long Term Fuel Trim significantly in the negative range (Rich condition)?

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Go to Step 14

Go to Step 15

1. Check the items that can cause the engine to run rich. Refer to DTC P0172 Fuel Trim System Rich for diagnosis. Make any necessary repairs.
2. Perform the exhaust emission test.

Does the vehicle pass the test?

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System OK

Go to Step 16

1. Check the items that can cause the engine to run lean. Refer to DTC P0171 Fuel Trim System Lean for diagnosis. Make any necessary repairs.
2. Perform the exhaust emission test.

Does the vehicle pass the test?

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System OK

Go to Step 16

1. Check the catalytic converter for lead contamination. An indication would be the removal of the fuel filler neck restrictor.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 20

Go to Step 17

1. Check for an engine mechanical problem. Perform a cylinder compression check Refer to Engine section .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 12

Go to Step 19

1. Check for a fouled Rear Heated Oxygen Sensor and replace as necessary. Refer to DTC P0138 HO2S Circuit High Voltage Sensor 2 Diagnostic Aids .
2. Replace the Catalytic Converter.

Is the action complete?

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Go to Step 20

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1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no malfunctions have been found, review/inspect the following items:

•	Visual/physical inspection.

•	Scan tool data.

•	All electrical connections within a suspected circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 20

Check for Service Bulletins

Operate vehicle within the conditions under which the original symptom was noted.

Does the system now operate properly?

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System OK

Go to Step 2