On GLC Wagon and B2000 models, connect voltmeter probes to throttle positioner 3-way solenoid electrical terminals without disconnecting electrical connector.
On GLC models, connect voltmeter probes to Brown/White and Yellow/Black terminals of engine speed switch. On 626 models, connect voltmeter probes to Green/White and Black/White wires of throttle positioner system electrical connector.
On all models, start and run engine at 2000 RPM (3000 RPM on GLC). Slowly decrease engine speed and note speed at which current flows to circuit (does not flow on GLC).
Engine speed should be 1400-1600 RPM on GLC Wagon and 626 models, 1600-1800 RPM on B2000 models and 2000-2200 RPM on GLC models.
On GLC and GLC Wagon models, increase engine speed again (2000 RPM on GLC and 2500 RPM on GLC Wagon), then decrease engine speed. Current should flow to circuit at 1430-1570 RPM on GLC models (2000-2200 RPM on GLC Wagon models).
On B2000 and 626 models, slowly increase engine speed and note speed at which current does not flow to circuit. The difference between the recorded speeds should be 150-250 RPM on B2000 models and 50-250 RPM on 626 models.
If engine speed switch does not operate as outlined, replace engine speed switch.

Fig 1: Mazda 626 Engine Speed Switch Test

Courtesy of MAZDA MOTORS CORP.

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.

Safety Warning

Engine Speed Switch