Action Taken When the DTC Sets

The ECM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the ECM stores this information in the Failure Records. If the diagnostic reports a failure on the second ignition cycle the ECM records the operating conditions at the time of the failure. The ECM writes the operating conditions to the Freeze Frame and updates the Failure Records. The ECM illuminates the MIL when one of the following occur:

• DTCs P0171 and P0172 are type B DTCs.
• The ECM detects the same fuel trim failure during 2 consecutive trips.
• The ECM detects any fuel trim failure during any subsequent trip if the conditions at the time of failure meet the following criteria:
  • The engine load is within 20 percent of the previous test that failed.
  • The engine speed is within 375 RPM of the previous test that failed.
  • The engine coolant temperature is in the same range of the previous test that failed.