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 voltmeter or appropriate scan tester. See RETRIEVING CODES . Engine Control Module (ECM) monitors several different engine control system circuits. If an abnormal input signal occurs, a fault code is stored in ECM memory and assigned a fault code number. Each circuit has its own fault number and message. A specific fault code indicates a particular system failure, but it does not indicate that cause of failure is necessarily within system.
A fault code does not condemn any specific component; it simply points out a probable malfunctioning area. If a fault code is set, ECM will turn on Malfunction Indicator Light (MIL). Fault codes can be confirmed by using a voltmeter. System malfunctions encountered are identified as either hard failures or intermittent failures as determined by ECM.
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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.