Electronic Ignition System Diagnosis
The ignition control (IC) module has independent power and ground circuits. The circuits between the IC module and the powertrain control module (PCM) consist of the following circuits:
• The IC timing signal
• The IC timing control
• The low-resolution engine speed signal
• A low reference signal
The ignition control (IC) module sends 3x signals to the powertrain control module (PCM). The IC module controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions:
• The PCM receives the second 3x signal.
• The PCM applies 5 volts to the IC timing signal circuit.
• The timing advance switches to PCM control.
The numbers below refer to the step numbers on the diagnostic table.
3.It is necessary to disconnect the 24 X crank sensor in order to ensure that the 7 X signal is read in the 3X reference parameter.
4.The J 26792 spark tester presents a more difficult load on the secondary ignition than a normal spark plug. If a miss or a hesitation is caused by a spark plug that is not firing, the spark tester should also not fire.
5.Use a 5 percent saltwater solution in a spray container to induce the voltage arcing 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 can also be performed by substituting a known good coil for the one causing the no spark condition.
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