Step
| Action
| Values
| Yes
| No
|
A vehicle fails an emission test. The vehicle has an excessive rotten egg smell. Excessive odors do not necessarily indicate excessive emissions.
|
1
| Were the Important Preliminary Checks performed?
| --
| Go to
Step 2
| Go to
Diagnostic Starting Point - Engine Controls
|
2
|
- Run the engine until it reaches operating temperature.
- Perform an emission test.
Did the vehicle pass the emission test?
| --
| System OK
| Go to
Step 3
|
3
|
- Connect the scan tool to the data link connector (DLC).
- Road test the vehicle.
- Monitor the long term fuel trim memory.
Is the long term fuel trim memory within the value specified?
| -20 to +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 P0171, P0172, P0174, or P0175
| Go to
Step 5
|
5
| Is the long term fuel trim memory above the value specified?
| 25%
| Go to
DTC P0171, P0172, P0174, or P0175
| --
|
6
|
- Check for a properly installed fuel cap.
- Check the fuel system pressure.
- Perform an injector diagnosis.
Is the problem found?
| --
| Go to
Step 7
| Go to
Step 8
|
7
|
- Repair or replace any fuel system components as needed.
- Perform an emission test.
Did the vehicle pass the emission test?
| --
| System OK
| --
|
8
|
- Inspect the ignition system for proper operation.
- Inspect the spark plugs for excessive wear, insulation cracks, improper gap, or heavy deposits.
- Inspect the ignition wires for cracking, hardness, or improper connections.
Is the problem found?
| --
| Go to
Step 9
| Go to
Step 10
|
9
|
- Repair or replace any ignition system components as needed.
- Perform an emission test.
Did the vehicle pass the emission test?
| --
| System OK
| --
|
10
|
- Inspect for vacuum leaks.
- Inspect the catalytic converter for contamination.
- Inspect for carbon buildup on the throttle body and the throttle plate and inside the engine. Remove with a top engine cleaner.
- Inspect the exhaust gas recirculation (EGR) valve for not opening.
- Inspect for proper positive crankcase ventilation (PCV) operation.
Are all inspections and needed repairs complete?
| --
| System OK
| --
|
