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.
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HOMESERVICE MANUALSMAZDA1999MX-5 MIATA L4-1.8L DOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTHROTTLE POSITION SENSORTESTING AND INSPECTION
1999 Mazda MX-5 Miata L4-1.8L DOHC
Throttle Position Sensor: Testing and Inspection
1999 Mazda MX-5 Miata L4-1.8L DOHCSECTION Testing and Inspection
NOTE:
- The throttle position sensor on this type of vehicle is a maintenance-free type.
- Perform the following test only when detected.
1. If not as PID value specified, inspect as follows:
- Verify that the throttle valve is fully closed.
- Accelerator cable the free play
- Throttle cable the free play
- Actuator cable the free play
2. If above specified okay, but PID value is out of specification, inspect as follows:
Open circuit
- Reference voltage circuit (Throttle position sensor connector terminal A and PCM connector terminal 21.)
- Throttle position circuit Throttle position sensor connector terminal C and PCM connector terminal 3E.)
- Ground circuit (Throttle position sensor connector terminal B and PCM connector terminal 3F.)
Short circuit
- Throttle position sensor connector terminal A and PCM connector terminal 21 to ground.
- Throttle position sensor connector terminal C and PCM connector terminal 3E to ground.
3. Reconnect the throttle position sensor connector.
4. If correct the above open or short circuit, replace throttle position sensor.
- The throttle position sensor on this type of vehicle is a maintenance-free type.
- Perform the following test only when detected.
1. If not as PID value specified, inspect as follows:
- Verify that the throttle valve is fully closed.
- Accelerator cable the free play
- Throttle cable the free play
- Actuator cable the free play
2. If above specified okay, but PID value is out of specification, inspect as follows:
Open circuit
- Reference voltage circuit (Throttle position sensor connector terminal A and PCM connector terminal 21.)
- Throttle position circuit Throttle position sensor connector terminal C and PCM connector terminal 3E.)
- Ground circuit (Throttle position sensor connector terminal B and PCM connector terminal 3F.)
Short circuit
- Throttle position sensor connector terminal A and PCM connector terminal 21 to ground.
- Throttle position sensor connector terminal C and PCM connector terminal 3E to ground.
3. Reconnect the throttle position sensor connector.
4. If correct the above open or short circuit, replace throttle position sensor.
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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.