GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Check for a plugged three-way converter (TWC), (which may have resulted from a serious engine malfunction).

Is the TWC plugged?

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Go to Step 2

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2

  1. Replace the TWC. Refer to Catalytic Converter Replacement .
  2. Check engine performance.
  3. Check for improper (leaded) fuel in the fuel tank.

Is there still a loss of engine power and/or internal rattles in the muffler?

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System OK.

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