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.
System Diagnosis: Notes
System diagnosis can be accomplished using a scan tool, the Malfunction Indicator Light (MIL) or a voltmeter. See ENTERING ON-BOARD DIAGNOSTICS . Powertrain Control Module (PCM) monitors several different engine control system circuits. If an abnormal input signal occurs, a trouble code is stored in PCM memory and assigned a trouble code number. Each circuit has its own trouble code number and message. A specific trouble code indicates a particular system failure, but does not indicate that cause of failure is necessarily within system.
A trouble code does not condemn any specific component; it simply points out a probable malfunctioning area. If a trouble code is set, PCM will turn on MIL. System malfunctions encountered are identified as either hard failures or intermittent failures as determined by PCM.
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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.