Ignition Coil Primary Circuit Switching Check
- Disconnect ignition module 3-wire connector and install diagnostic adapter (T79P-12127-A or equivalent). Connect a test light between "TACH" terminal of ignition coil and an engine ground. With ignition switch in "RUN" position, touch diagnostic adapter test lead to positive battery terminal.
- Test light should flash each time test lead is either connected to or removed from battery terminal. Turn ignition switch to "OFF" position, remove diagnostic adapter, and reconnect ignition module wires. If test light flashes, proceed to "IGNITION COIL SECONDARY RESISTANCE CHECK ". If test light does not flash or is dim, proceed to "VOLTAGE SUPPLY CIRCUITS CHECK ".