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.
EGI Control System: Description
The Mazda Electronic Gas Injection (EGI) computerized engine control system monitors various engine/vehicle functions to control engine operation and lower emissions while maintaining good fuel economy and driveability.
The Electronic Control Unit (ECU), through various input sensors, monitors battery voltage, engine RPM, amount of intake air, cranking signal, crankshaft angle, intake temperature, radiator and engine coolant temperatures, oxygen concentration in exhaust gases, throttle opening, atmospheric pressure, gearshift lever position, clutch engagement, braking, and A/C compressor operation. The ECU uses all input information to control fuel injection, and output devices. See Fig 1 and Fig 2 .
The ECU has a built-in fail-safe mechanism. If a fault occurs while driving, the ECU will substitute pre-programmed values. Driving performance will be affected, but the vehicle may still be driven.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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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