Electronic Ignition (EI) System Diagnosis

CIRCUIT DESCRIPTION
During cranking, the Ignition Control (IC) module monitors the 7X Crankcase Position (CKP) sensor input for recognition of the CKP 1 signal. The CKP 1 signal is used only by the IC module for synchronization at start-up to determine the correct cylinder pair to spark. Once the engine speed reaches approximately 600 RPM, the Powertrain Control Module (PCM) sends 5.0 volts to the IC timing signal circuit at the IC module causing the IC timing control circuit to become ungrounded allowing the medium resolution engine speed signal to be used for better low engine speed performance. At higher engine speeds (1,650+) the PCM uses the low resolution engine speed signal to control ignition timing because a higher resolution signal is not needed. In this ignition system, neither end of the secondary winding is grounded. Instead, each end of a coils secondary winding is attached to a spark plug. Each cylinder is paired with the cylinder that is opposite it (1-4, 2-5, 3-6). These two plugs are on companion cylinders, i.e., on top dead center at the same time. When the coil discharges, both plugs fire at the same time to complete the series circuit. The cylinder on compression is said to be the event cylinder and the one on exhaust is the waste cylinder. The cylinder on the exhaust stroke requires very little of the available energy to fire the spark plug. The remaining energy will be used as required by the cylinder on the compression stroke. The same process is repeated when the cylinders reverse roles. This method of ignition is called a waste spark ignition system. This table assumes there are no ignition system, fuel injector, cam sensor, or crank sensor DTCs present. The electronic ignition system check tests for faulty ignition coils, spark plugs, plug wires, the 7X crank sensor, and IC module. This table requires the J 26792 spark tester.

TEST DESCRIPTION

Steps 1-4:

Steps 5-13:

Steps 14-23:

The numbers below refer to the step numbers on the diagnostic table.
3. It is necessary to disconnect the 24X crank sensor to ensure that the 7X signal is being read in the 3X reference parameter on the scan tool.
4. The J 26792 presents a more difficult load on the secondary ignition than a normal spark plug. If a miss, stumble, or hesitation is being caused by a spark plug not firing, the spark tester should also not fire.
5. Use a 5 percent saltwater solution in a spray bottle to induce voltage arching to ground through faulty insulation of spark plug wires.
7. If the no spark condition follows the suspected coil, that coil is faulty. Otherwise, the ignition module is the cause of no spark. This test could also be performed by substituting a known good coil for the one causing the no spark condition.