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 MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODES - 1.9LTEST DP - VEHICLE SPEED SENSOR (VSS)DIAGNOSTIC AIDS

1991 Mercury Tracer Base, 4D Sedan, Automatic

Diagnostic Aids

1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Diagnostic Aids

Perform this test when directed by QUICK TEST.

This CIRCUIT TEST is intended to diagnose the following:

VSS harness circuits
Vehicle Speed Sensor (VSS)
ECA

Fig 1: Vehicle Speed Sensor Circuit

TEST PIN WIRE COLOR IDENTIFICATION

Application	Wire Color
Pin 3 (VSS +)	White/Black
Pin 6 (VSS -)	Blue

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.