Part 3 of 3

Chart A-3:

Ignition Circuit:

CIRCUIT DESCRIPTION:
If the Tech 1 scan tool did not indicate a cranking RPM and there is no spark present at the plugs, the problem lies in the electronic ignition system or the power and ground supplies to the module.

The magnetic crankshaft position sensor is used to determine engine crankshaft position much the same way as the pick-up coil did in distributor type systems. The sensor is mounted in the block near a seven slot wheel on the crankshaft. The rotation of the wheel creates a flux change in the sensor which produces a voltage signal. The ignition control module then processes this signal and creates the reference pulses needed by the ECM and the signal triggers the correct coil at the correct time.

TEST DESCRIPTION: Number(s) below refer to circled number(s) on the diagnostic chart.

1. This test will determine if the 12 volts supply and a good ground is available at the ignition module.

2. Tests for continuity of CKT 439 to the ignition control module. If test light does not light but the MIL is "ON" with ignition "ON," repair open in CKT 439 between Electronic Ignition (EI) control module and splice.

3. Checks for continuity of the crankshaft position sensor and connections.

4. Voltage will vary in this test depending on cranking speed of engine.