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Hard Or Intermittent Trouble Code Determination

NOTE: DTCs will be recorded at various operating times. Some DTCs require operation of related sensor or switch for 5 seconds; others require operation for 5 minutes or more at normal operating temperature, vehicle speed and load. Therefore, some DTCs may not set in a service bay operational mode and may require road testing vehicle in order to duplicate conditions under which DTC will set.

During any diagnostic procedure, determine if DTCs are hard failure DTCs or intermittent failure DTCs. Diagnostic procedures will not always help analyze intermittent DTCs. To determine hard and intermittent DTCs, perform the following:

  1. Enter diagnostic mode. Read and record all stored DTCs. Exit diagnostic mode, and then clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES .
  2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. MIL should turn off. Operate warm engine at specified RPM for 2 minutes and note MIL.
  3. If MIL illuminates, enter diagnostic mode. Read and record DTCs. This will reveal hard failure codes. If MIL does not illuminate, all stored DTCs were intermittent failures, except as noted above.

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