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 DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 13 (ENGINE CONTROLS - TESTS W/CODES - EEC 1.8L)CIRCUIT TESTSCIRCUIT TEST STP - SWITCH TO POWERSWITCH PERFORMANCE CHECK
1991 Mercury Tracer Base, 4D Sedan, Automatic
Switch Performance Check
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Switch Performance Check
WARNING: This page is about a different car, the 1994 Mercury Tracer and 1994 Ford Escort. However, it is still accessible from the selected car via links, so may be relevant.
Check switch in ON and OFF positions. Install breakout box, leaving PCM disconnected. Turn ignition on. Measure voltage between breakout box test pin of switch being tested and ground. Switch should function as follows:
- BOO Depress brake pedal to close switch. Battery voltage should be present.
- DEF Turn rear defroster on to close switch. Battery voltage should be present.
- HDLT Turn headlight on to close switch. Battery voltage should be present.
- VST Switch is closed when engine is cranking. About 9 volts should be present.
RENDER: 1.0x
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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.