Diagnostic Aids

Major differences between Computer Controlled Dwell (CCD) and non-CCD systems is the CCD system does not receive a START signal from the ignition switch, at TFI module (terminal No. 4), during engine cranking. CCD systems send an additional coil negative (-)/tach circuit signal to ECA from ignition module (terminal No. 4) labeled Filtered Tach Output (FTO). The following information should be noted during testing:

• A spark plug with a broken side electrode is NOT sufficient to check for spark and may lead to incorrect results.
• When instructed to inspect a wiring harness, both a visual inspection and a continuity test should be performed.
• When making measurements on a wiring harness or connector, perform a WIGGLE test while measuring.
• References to SPOUT in-line connector apply to both in-line and shorting-bar type connectors.
• Test procedures are intended to identify faulty components or wiring while fault is present. If complaint is an intermittent condition, see the TESTS W/O CODES article in this section.