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.
Diagnostic Aids
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.
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