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.
2004 Mazda MX-5 Miata Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Wave Profile Inspection
- Remove the PCM. See PCM REMOVAL/INSTALLATION .
- Connect WDS or equivalent to DLC-2 connector.
- Connect oscilloscope test leads to the following PCM connector terminals.
- (+) lead: PCM terminal 3V
- (-) lead: PCM terminal 4A
- Start the engine.
- Monitor RPM PID.
- Inspect wave profile when idling engine.
- If wave profile or voltage are out of specifications, carry out the "Circuit Open/Short Inspection". See CIRCUIT OPEN/SHORT INSPECTION .
- PCM terminal: 3V(+) <-> 4A(-)
- Oscilloscope setting: 2.0V/DIV(Y), 20ms/ DIV(X), DC range
- Vehicle condition: Idling
- If wave profile or voltage are out of specifications, carry out the "Circuit Open/Short Inspection". See CIRCUIT OPEN/SHORT INSPECTION .
Factory Service Tools
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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.
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