Diagnostic Aids

• The catalyst test may abort due to a change in the engine load. Do not change the engine load, ensure the AC is OFF, the coolant fan is not cycling, while a catalyst test is in progress.
• Driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present.
• These conditions may cause a catalytic converter to degrade. Inspect for the following conditions:
  • An engine misfire
  • High engine oil or high coolant consumption
  • Retarded spark timing
  • A weak or poor spark
  • A lean fuel mixture
  • A rich fuel mixture
  • A damaged oxygen sensor or wiring harness.
  • If an intermittent condition cannot be duplicated, the information included in Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was set.
• The catalyst may have been temporarily contaminated with a chemical from a fuel additive, fuel contamination or any of the above conditions.

If the condition is determined to be intermittent, refer to Testing for Intermittent Conditions and Poor Connections .