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 3 L4-2.3LFACTORY OEM SERVICE PROCEDURE
Vehicle Speed Sensor (VSS) Inspection
VEHICLE SPEED SENSOR (VSS) INSPECTION
1. Connect the WDS or equivalent, drive the vehicle, and verify the input value of the OSS PID. If the input value is 0 rpm, perform the Power Supply Voltage Inspection, Open Circuit Inspection, or Short Circuit Inspection. If the input value is other than 0 rpm, perform the Visual Inspection or Wave Profile Inspection.
Visual Inspection
1. Remove the VSS.
2. Verify that the sensor is free of any metallic shavings or particles.
^ If there is any malfunction, clean them off.
3. Install the VSS.
Wave Profile Inspection
1. Remove the PCM.
2. Connect WDS or equivalent to DLC-2.
3. Connect oscilloscope test leads to the following PCM connector terminals.
^ (+) lead: PCM terminal 1J
^ (-) lead: PCM terminal 1BD
4. Start the engine.
5. Monitor VSS PID.
6. Inspect wave profile.
^ PCM terminal: 1J (+)-1BD
^ Oscilloscope setting: 1 V/DIV (Y), 2.5 ms/DIV (X), DC range
^ Vehicle condition: drive the vehicle at 32 km/h (20 mph) - If there is any malfunction, perform the Open Circuit Inspection or Short Circuit Inspection.
Power Supply Voltage Inspection
1. Disconnect the VSS connector.
2. Turn the ignition switch to the ON position.
3. Measure voltage at VSS terminal B.
^ If voltage is normal, go to Open Circuit Inspection and Short Circuit Inspection.
^ If there is any malfunction, repair wiring harness between VSS and PCM.
Specification 4.5 - 5.5 V
Open Circuit Inspection
1. Inspect the following circuit for open.
^ Power circuit (VSS terminal A to main relay terminal D)
^ Ground circuit (VSS terminal C to GND)
^ if an open circuit or short circuit is found, repair the malfunctioning wiring harness.
^ If there are no open or short circuits, perform the sensor rotor inspection.
Short Circuit Inspection
1. Inspect the following circuit for short circuit.
^ Power circuit (VSS terminal A to main relay terminal D)
^ If an open circuit or short circuit is found, repair the malfunctioning wiring harness.
^ If there are no open or short circuits, perform the sensor rotor inspection.
Sensor Rotor Inspection
1. Remove the VSS.
2. Shift the selector lever to N position.
3. Inspect sensor rotor surface via VSS installation hole while rotating the front tire manually
1. Is the sensor rotor free of damage and cracks?
2. Is the sensor rotor free of any metallic shavings or particles?
^ If the sensor rotor is normal, replace the VSS.
^ If there is any malfunction, clean or replace the sensor rotor.
1. Connect the WDS or equivalent, drive the vehicle, and verify the input value of the OSS PID. If the input value is 0 rpm, perform the Power Supply Voltage Inspection, Open Circuit Inspection, or Short Circuit Inspection. If the input value is other than 0 rpm, perform the Visual Inspection or Wave Profile Inspection.
Visual Inspection
1. Remove the VSS.
2. Verify that the sensor is free of any metallic shavings or particles.
^ If there is any malfunction, clean them off.
3. Install the VSS.
Wave Profile Inspection
1. Remove the PCM.
2. Connect WDS or equivalent to DLC-2.
3. Connect oscilloscope test leads to the following PCM connector terminals.
^ (+) lead: PCM terminal 1J
^ (-) lead: PCM terminal 1BD
4. Start the engine.
5. Monitor VSS PID.
6. Inspect wave profile.
^ PCM terminal: 1J (+)-1BD
^ Oscilloscope setting: 1 V/DIV (Y), 2.5 ms/DIV (X), DC range
^ Vehicle condition: drive the vehicle at 32 km/h (20 mph) - If there is any malfunction, perform the Open Circuit Inspection or Short Circuit Inspection.
Power Supply Voltage Inspection
1. Disconnect the VSS connector.
2. Turn the ignition switch to the ON position.
3. Measure voltage at VSS terminal B.
^ If voltage is normal, go to Open Circuit Inspection and Short Circuit Inspection.
^ If there is any malfunction, repair wiring harness between VSS and PCM.
Specification 4.5 - 5.5 V
Open Circuit Inspection
1. Inspect the following circuit for open.
^ Power circuit (VSS terminal A to main relay terminal D)
^ Ground circuit (VSS terminal C to GND)
^ if an open circuit or short circuit is found, repair the malfunctioning wiring harness.
^ If there are no open or short circuits, perform the sensor rotor inspection.
Short Circuit Inspection
1. Inspect the following circuit for short circuit.
^ Power circuit (VSS terminal A to main relay terminal D)
^ If an open circuit or short circuit is found, repair the malfunctioning wiring harness.
^ If there are no open or short circuits, perform the sensor rotor inspection.
Sensor Rotor Inspection
1. Remove the VSS.
2. Shift the selector lever to N position.
3. Inspect sensor rotor surface via VSS installation hole while rotating the front tire manually
1. Is the sensor rotor free of damage and cracks?
2. Is the sensor rotor free of any metallic shavings or particles?
^ If the sensor rotor is normal, replace the VSS.
^ If there is any malfunction, clean or replace the sensor rotor.
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.