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HOMESERVICE MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 5 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - EEC-IV)IGNITION SYSTEMDI SYSTEMDIAGNOSTIC AIDS
1991 Mercury Tracer Base, 4D Sedan, Automatic

Diagnostic Aids

1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 1993 Mercury Tracer, 1993 Mercury Topaz, 1993 Mercury Sable, 1993 Mercury Grand Marquis, and 1993 Mercury Cougar. However, it is still accessible from the selected car via links, so may be relevant.

Major difference between Computer Controlled Dwell (CCD) and non-CCD systems is CCD system does not receive a start signal from ignition switch at ICM (terminal No. 4) during engine cranking. CCD systems send an additional coil negative (-)/tach circuit signal to PCM from ignition module (terminal No. 4) labeled Filtered Tach Output (FTO). Following information should be noted during testing:

  • All voltage readings given in test procedures are based on values obtained using a standard DVOM such as Rotunda (007-00001) or Fluke (20 or 70 Series). DO NOT use RMS type meter.
  • When instructed to inspect a wiring harness, perform both a visual inspection and a continuity test.
  • When making voltage checks, ground connections should be made at negative battery terminal or cast iron surface of engine.
  • When making measurements on a wiring harness or connector, perform a wiggle test while measuring.
  • When making voltage checks, ground readings are defined as a value of less than 1.0 volt. Battery voltage is defined as a value of 10-14 volts.
  • Test procedures are intended to identify faulty components or wiring while fault is present. If complaint is an intermittent condition, refer to appropriate H - EEC-IV TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
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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.