Ignition System Check

IGNITION SYSTEM CHECK

Electronic Ignition System Check:

CIRCUIT DESCRIPTION
A magnetic Crankshaft Position (CKP) sensor is used to determine engine crankshaft position, much the same way as the pick-up coil did in Distributor Ignition (DI) type systems. The sensor is mounted in the block, near a slotted wheel on the crankshaft. The rotation of the wheel creates a flux change in the sensor, which produces a voltage signal. The Electronic Ignition Control Module (ICM) processes this signal and creates the reference pulses needed by the Powertrain Control Module (PCM) to trigger the correct coil at the correct time.

If the scan tool did not indicate cranking RPM, and there is no spark present at the plugs, the problem lies in the ICM, CKP sensor or the power and ground supplies to the ICM.

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

1. The Electronic Ignition (EI) system uses two plugs and cables to complete the circuit of each coil. The companion spark plug cable in the circuit must be connected to a good ground.
2. This test will determine if the 12 volt supply and a good ground is available at the electronic Ignition Control Module (ICM).
3. This test will determine if the ICM is not generating the reference pulse, or if the wiring or PCM are at fault. By touching and removing a test light to 12 volts on Circuit (CKT) 430, a reference pulse should be generated. If RPM is indicated, the PCM and wiring are OK.
4. This test will determine if the ICM is not triggering the problem coil, or if the tested coil is at fault. This test could also be performed by substituting a known good coil. The secondary coil winding can be checked with a Digital Voltmeter (DVM). There should be 5,000 to 10,000 ohms across the coil towers. There should not be any continuity from either coil tower to ground.
5. Checks for continuity of the crankshaft position sensor and connections.
6. Normal crankshaft position sensor voltage output range is 0.8 to 1 A volt (9800 to 1400 mV) with a fully charged battery and engine at room temperatures. Minimum output voltage (slow craning, low battery) can be as low as 0.3 volt (300 mV).