Circuit Description
The Catera 3.0L V6 is equipped with a Distributorless Ignition System (DIS). In this ignition system, both ends of each of the three ignition coils are connected to a spark plug. A pair of cylinders share one coil in the following arrangement: 1 and 4, 2 and 5, 3 and 6. Each coil is connected to spark plugs on companion cylinders, for example, on top center at the same time. One cylinder is on the compression stroke when the other one is on the exhaust stroke.
When the coil discharges, both of the plugs fire at the same time by using the engine block in order to complete the electrical circuit. The cylinder on the compression stroke is called the event cylinder and the cylinder on the exhaust stroke is called the waste cylinder. The two cylinders share the energy that is available from the ignition coil to fire both of the spark plugs. This method of ignition is called the waste spark ignition.
The Catera DIS system consists of the coil pack and the ECM. There is no separate ignition control module. The ECM performs all of the ignition control module functions. The Ignition Coil assembly is powered by an ignition feed circuit. The remaining three wires go to the ECM and are the Ignition Control (IC) circuits. The ECM causes a spark to occur by pulsing an IC circuit, which triggers an ignition coil and fires the appropriate pair of spark plugs. The ECM controls the sequencing and the timing.
Diagnostic Aids
Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.
Test Description
The number(s) below refer to the step numbers on the diagnostic table:
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The scan tool output control commands the ECM in order to pulse the IC circuit to ground about 5 times per second. The Ignition control pulses have a very short pulse width (about 1 ms). The test light will blink with each pulse but will be dimly illuminated due to the very short on-time.
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Recheck the system for multiple problems that may be related (for example, fouled spark plugs caused by the fuel system compensating for a misfiring cylinder).
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Powertrain Powertrain On Board Diagnostic (OBD) System Check
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2 |
Does the test light illuminate? | -- | ||||||||
Perform the following test on the IC circuit for coil 1-4. Then repeat the procedure for coil 2-5 and 3-6:
The test light should flash on and off (dimly) as long as the Ignition Coil 1-4 output is being controlled. Repeat the test on the remaining IC circuits. Does the test light flash on and off for all of the three ignition coil output circuits? | -- | |||||||||
4 |
Did the plug wires pass the visual inspection and is the resistance within the specified range? | 1-3-5-7-9K ohms 2-4-6K ohms 2-6K ohms | ||||||||
5 | Use the DVM J 39200 in order to measure the resistance of the coil primary winding for each ignition coil (one lead connected to the B+ feed terminal, the other to the IC circuit terminal for the coil being tested, in the coil assembly connector). Is the resistance within the specified range on all three ignition coils? | 0.4-0.6 ohms at 20°C (68°F) | ||||||||
6 | Use the DVM J 39200 in order to measure the resistance of the coil secondary winding for each ignition coil (tower to tower, on the coil being tested). Is the resistance within the specified range on all three ignition coils? | 10 K-14 K ohms at 20°C (68°F) | ||||||||
7 |
Is continuity indicated? | -- | ||||||||
8 | Use DVM J 39200 in order to check the harness for continuity to ground on the IC circuit(s) that did not flash the test light. Is continuity indicated? | -- | ||||||||
9 |
Does the test light illuminate? | -- | ||||||||
10 | Repair the ignition feed circuit. Is the action complete? | -- | -- | |||||||
11 | Repair the open/high resistance IC circuit. Is the action complete? | -- | -- | |||||||
12 | Repair the IC circuit shorted to ground. Is the action complete? | -- | -- | |||||||
13 | Repair the IC circuit shorted to B+. Is the action complete? | -- | -- | |||||||
14 | Check for a poor connections or poor terminal tension at the Ignition Coil harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||||||||
15 |
Is continuity indicated? | -- | ||||||||
16 | Repair the IC circuits that are shorted together. Is the action complete? | -- | -- | |||||||
17 | Replace the ignition coil assembly. Is the action complete? | -- | -- | |||||||
18 | Replace the failed spark plug wire(s). Is the action complete? | -- | -- | |||||||
19 | Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||||||||
20 |
Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | -- | |||||||
Does the engine start and continue to run? | -- | |||||||||
22 |
Are there any DTCs displayed? | -- | Go to the applicable DTC table | |||||||
23 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK |
