During any diagnostic procedure, determine if DTC(s) are hard failure DTCs or intermittent failure DTCs. Diagnostic procedures will not always help analyze intermittent DTCs. To determine hard DTCs and intermittent DTCs:

Enter diagnostic mode. Read and record all stored DTCs. Exit diagnostic mode and clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES .
Apply parking brake and place transmission in Neutral or Park. Block drive wheels and start engine. MIL should turn off. Allow engine to reach normal operating temperature and continue to run for 2 minutes and note MIL.
If MIL illuminates, enter diagnostic mode. Read and record DTCs. This will reveal hard failure DTCs. Oxygen sensor-related DTCs may require a road test to reset hard failures after DTCs were cleared.
If MIL does not illuminate, all stored DTCs were intermittent failures.

NOTE: DTCs will be recorded at various operating times. Some DTCs require operation of that sensor or switch for 5 seconds; others require operation for 5 minutes or longer 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.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Hard Or Intermittent Trouble Code Determination

Use the Manual With the Right Hardware

When to See a Mechanic

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