Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Intermittent Diagnostic Techniques: Notes
Intermittent diagnostic techniques help find and isolate the root cause of intermittent faults associated with the electronic engine control (EEC) system. The information is organized to help find the fault and carry out the repair. The process of finding and isolating an intermittent starts with recreating a fault symptom, accumulating PCM data, and comparing that data to typical values, then analyzing the results. Refer to the diagnostic tool user manual for the functions described below.
Before proceeding, be sure that:
- Customary mechanical system tests and inspections do not reveal a concern. NOTE: Mechanical component conditions can make a PCM system react abnormally.
- Technical Service Bulletins (TSBs), if available, are reviewed.
- Quick Test and associated diagnostic subroutines have been completed without finding a fault, and the symptom is still present.
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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.