Test 5 - Signal Testing

System Schematic:

1. Use an oscilloscope or a logic probe to test for crank angle sensor signal at terminal # 21 of the Multipoint Fuel Injection (MPI) computer terminal. If no signal is present while cranking check wiring between the T.D.C. sensor and the MPI computer and repair as necessary. If the signal is present refer to step 2.

2. While cranking the engine use an oscilloscope or a logic probe to test for Top Dead Center (TDC) sensor signal at pin # 22 of the Multipoint Fuel Injection (MPI) computer terminal. If a signal is not present check wiring and repair as necessary, then retest. If signal is present go to step # 3.

3. Check pins # 55 and # 54 of the Multipoint Fuel Injection (MPI) computer for output signals to the power transistor. For additional diagnosis if signals are not present refer to COMPUTERIZED ENGINE CONTROLS.
If signal is present check coil connector pin # 4 for battery voltage with the key in the on position. If voltage is not present check wiring and repair as necessary, then retest. If voltage is present and there is no secondary coil output replace coil. If voltage is present and there is secondary coil output, check spark plug condition and replace if necessary. If plug condition is OK and engine still does not run the ignition system is working correctly, check computerized engine controls.