Circuit Description
This system includes the Distributor, the ignition coil, the ignition control module, the secondary wires, spark plugs, the VCM and the crank sensor. The ignition system is controlled by the Vehicle Control Module (VCM). The VCM monitors the information from various engine sensors, computes the desired spark timing and controls the dwell and firing of the ignition coil via an (IC) line to the ignition control module.
Diagnostic Aids
Check the following items:
The IC control circuit for an intermittent short to ground.
Check the following when the distributor rotor does not rotate, while engine is cranking:
| • | A broken distributor drive shaft |
| • | A worn distributor drive gear or camshaft timing chain and gears |
An intermittent may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation. Thoroughly check any circuity that is suspected of causing the intermittent complaint for the following conditions:
| • | Backed out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal to wire connections |
| • | Physical damage to the wiring harness |
| • | Corrosion |
| • | Moisture in the connector |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
The battery should be fully charged prior to any tests.
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Perform the OBD system check before proceeding unless it was already performed.
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Checks for proper output from the enhanced ignition system. The spark tester requires a minimum of 25,000 volts to operate. This check can be used in case of an ignition miss, because the system may provide enough voltage to run the engine but not enough operate a spark plug under heavy load.
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This test separates the distributor cap, rotor, and ignition wires from the ignition coil in order to help identify a secondary ignition system problem.
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This step determines the proper available voltage exists in the primary ignition circuit. This also checks the ignition coil and wiring.
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This test checks the ignition control module, connection and wiring.
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This test begins to determine if the VCM is providing a signal to the ignition control module. If the VCM is not providing a signal to the ignition control module, the problem exists between the ignition control module and the VCM.
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This test checks for a basic engine mechanical problem.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure Records for reference. The control module's data is deleted once the Clear Info function is used. Did you perform the Powertrain ON-Board Diagnostic (OBD) System Check? | -- | |||||||||||
Is adequate spark present? | -- | Go to Hard Start | ||||||||||
Is adequate spark present? | -- | |||||||||||
4 | Measure the coil wire resistance using a J 39200 DMM. The resistance should be approximately the specified value. Is the resistance within the specified value? | 1000 ohms/inch | ||||||||||
Does the voltage measure above the specified value? | 10.0V | |||||||||||
6 | Measure the ignition control module harness connector terminal D voltage with a J 39200 DMM connected to a ground. Does the voltage measure above the specified value? | 10.0V | ||||||||||
Probe the ignition control module connector terminal C with test lamp connected to the B+ terminal. Is the test lamp ON? | -- | |||||||||||
8 |
Is the test lamp flashing? | -- | ||||||||||
9 |
Does the voltage measure above the specified value? | 10.0V | ||||||||||
10 |
Is the circuit open? | -- | ||||||||||
11 | Probe the ignition coil connector terminal C with a test lamp connected to B+. Is the test lamp ON? | -- | ||||||||||
12 | Probe the ignition coil connector terminal B with a test lamp connected to B+. IS the test lamp ON? | -- | ||||||||||
Is the voltage between the specified values? | 1.0-4.0V | |||||||||||
14 |
Are any of these conditions present? | -- | ||||||||||
Did the distributor rotor turn? | -- | Go to Symptoms | ||||||||||
16 |
Is the circuit open? | -- | ||||||||||
17 | Probe the VCM C3 harness connector pin 9 for the ignition control (IC) circuit with a test lamp connected to the B+ terminal. Is the test lamp ON? | -- | ||||||||||
18 |
Is the test lamp ON? | -- | ||||||||||
19 | Check for a poor ignition feed circuit to terminal A of the ignition control module. Did you find a problem.? | -- | -- | |||||||||
20 | Check for a poor ignition feed circuit to terminal A of the ignition coil. Did you find a problem? | -- | -- | |||||||||
21 | Check for a poor ignition control module connection. Did you find a problem? | -- | ||||||||||
22 | Check for a poor ignition coil connection. Did you find a problem? | -- | ||||||||||
23 | Check for a poor VCM connection. Did you find a problem? | -- | ||||||||||
24 | Repair the open ignition control module ground circuit. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
25 | Repair the IC circuit between the VCM and the control module. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
26 | Repair grounded IC circuit between the VCM and the ignition control module. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
27 | Repair short to voltage in the IC circuit between the VCM and the ignition control module. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
28 | Repair open tachometer signal circuit between the ignition coil and the ignition control module. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
29 | Repair the short to ground in the tachometer signal circuit between the ignition coil and the ignition control module. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
30 | Repair the short to ground in the tachometer signal circuit between the ignition coil and the instrument cluster. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
31 | Repair the circuit as necessary. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
32 | Replace the ignition coil. Refer to Ignition Coil and ICM Replacement in Engine Electrical. Is the action complete? | -- | -- | |||||||||
33 | Replace the coil wire. Is the action complete? | -- | -- | |||||||||
34 | Replace the distributor rotor. Is the action complete? | -- | -- | |||||||||
35 | Replace the distributor cap. Is the action complete? | -- | -- | |||||||||
36 | Replace the ignition control module. Refer to Ignition Coil and ICM Replacement in Engine Electrical. Is the action complete? | -- | -- | |||||||||
37 |
Refer to Crankshaft Position System Variation Learn . Is the action complete? | -- | -- | |||||||||
38 | Operate vehicle within the conditions under which the original symptom was noted. Does the system now operate properly? | -- | System OK |
