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 MANUALSMAZDA2005MX-5 MIATA L4-1.8L DOHCREPAIR AND DIAGNOSISRELAYS AND MODULESRELAYS AND MODULES - TRANSMISSION AND DRIVETRAINRELAYS AND MODULES - A/TCONTROL MODULETESTING AND INSPECTION
2005 Mazda MX-5 Miata L4-1.8L DOHC
Control Module: Testing and Inspection
2005 Mazda MX-5 Miata L4-1.8L DOHCSECTION Testing and Inspection
TRANSMISSION CONTROL MODULE (TCM) INSPECTION
1. Turn the ignition switch to the ON position, and inspect the TCM terminal voltage, referring to the Terminal Voltage Chart.
- If any TCM terminal voltage is incorrect, inspect the related input of output devices and wiring.
- If no problem is found, replace the TCM.
Note: Use the ground of terminal AP of the TCM when measuring terminal voltage as an error may occur when the negative (-) lead of the circuit tester is connected to ground.
Terminal Voltage Table (Reference Data)
1 of 4
2 of 4
3 of 4
4 of 4
Input/Output Pulse (Reference) input/turbine speed sensor
- Connecting terminal: W (+)-AP (-)
- Measuring device setting: 1 V/DIV (Y) 5 ms/DIV
- Measuring condition: Idle
Vehicle speed signal
- Connecting terminal: AC (+)-AP (-)
- Measuring device setting: lV/DIV (Y) 5ms/DIV (X)
- Measuring condition: Vehicle speed at 30 km/h (18.6 mph)
Output speed sensor Connecting terminal: AF (+)-AP (-)
- Measuring device setting: 1V/DIV (Y) 5ms/DIV (X)
- Measuring condition: Vehicle speed at 30 km/h (18.6 mph)
Engine speed signal
- Connecting terminal: AG (+)-AP (-)
- Measuring device setting: 2V/DIV (Y) 5 ms/DIV (X)
- Measuring condition: Idle
1. Turn the ignition switch to the ON position, and inspect the TCM terminal voltage, referring to the Terminal Voltage Chart.
- If any TCM terminal voltage is incorrect, inspect the related input of output devices and wiring.
- If no problem is found, replace the TCM.
Note: Use the ground of terminal AP of the TCM when measuring terminal voltage as an error may occur when the negative (-) lead of the circuit tester is connected to ground.
Terminal Voltage Table (Reference Data)
1 of 4
2 of 4
3 of 4
4 of 4
Input/Output Pulse (Reference) input/turbine speed sensor
- Connecting terminal: W (+)-AP (-)
- Measuring device setting: 1 V/DIV (Y) 5 ms/DIV
- Measuring condition: Idle
Vehicle speed signal
- Connecting terminal: AC (+)-AP (-)
- Measuring device setting: lV/DIV (Y) 5ms/DIV (X)
- Measuring condition: Vehicle speed at 30 km/h (18.6 mph)
Output speed sensor Connecting terminal: AF (+)-AP (-)
- Measuring device setting: 1V/DIV (Y) 5ms/DIV (X)
- Measuring condition: Vehicle speed at 30 km/h (18.6 mph)
Engine speed signal
- Connecting terminal: AG (+)-AP (-)
- Measuring device setting: 2V/DIV (Y) 5 ms/DIV (X)
- Measuring condition: Idle
RENDER: 1.0x
NO RELATED
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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.