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Ignition Coils/Modules
The electronic ignition system uses an individual ignition coil for each cylinder. There are two separate ignition module assemblies located in the camshaft cover of each cylinder bank. Each ignition module assembly contains an ignition control module and four ignition coils. Each ignition coil connects directly to a spark plug using a boot. This arrangement eliminates the need for secondary ignition wires. The ignition module assemblies receive power from a fused ignition feed. Both ignition module assemblies connect to chassis ground. A Reference Low and four ignition control (IC) circuits connect each ignition module assembly to the PCM. The PCM uses the individual IC circuits to control coil sequencing and spark timing for each ignition coil. The IC circuits transmit timing pulses from the PCM to the ignition control module to trigger the ignition coil and fire the spark plug. The PCM controls ignition system sequencing and timing events.
This ignition system produces very high energy to fire the spark plug. There is no energy loss because of ignition wire resistance, or the resistance of the waste spark system. Also, since the firing is sequential, each coil has seven ignition events to saturate as opposed to the three in a waste spark arrangement.
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Reference Low Circuits
The reference low circuits provide a common ground between the PCM, and the ignition control modules. These circuits reduce the electrical ground shifts that may occur between the PCM and the ignition control modules. A malfunction in the reference low circuits may cause a poor driveability condition.
Results of Incorrect Operation
An Ignition control circuit that is open, grounded, or shorted to voltage will set an ignition control circuit DTC. If a fault occurs in the IC output circuit when the engine is running, the engine will experience a misfire. DTCs P0351-P0358 indicate that the PCM detects a short to ground on an Ignition Control circuit. DTCs P1359 or P1360 will set when the PCM detects an open, a short to voltage on an IC circuit(s) that involve a cylinder group (i.e., cylinders 1/4/6/7 or 2/3/5/8). If both DTC P1359 and P1360 set, the most likely cause is a disconnected ignition coil cassette harness connector. An IC circuit shorted to voltage results in a loss of two cylinders within the specific cylinder group. For example, if the IC circuit for cylinder 1 is shorted to voltage, a loss of both IC circuits for cylinder 1 and cylinder 7 will occur.
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Document ID# 575142
2000 Cadillac Eldorado
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Secondary Ignition Diagnosis
Circuit Description
The Secondary Ignition Diagnosis tests the spark plugs, ignition coils, and ignition control modules. The PCM causes a spark to occur by grounding the IC circuit, which signals the ignition control module to trigger the ignition coil and fire the spark plug. The PCM controls the sequencing and timing of the spark based on the crankshaft and camshaft sensors input.
Diagnostic Aids
When servicing the ignition system components, use the following recommended procedures:
• If a boot remains attached to a coil or spark plug, twist the boot prior to removal.
• Inspect the boot for a missing or damaged internal spring.
• Do not re-install any component that has visible signs of damage.
• Install the boots onto the coils (until bottomed out). Then install the assembly onto the spark plugs. If this is not possible due to space limitations, start the boots onto the spark plugs and then install the coil assembly as straight down onto the plugs as possible.
• Ensure the boots are installed right side up.
• Lift the module beauty cover at the end opposite the module to remove.
• Repair a torn perimeter seal with RTV sealant.
• Adhere to the torque specifications when installing the coil cassette to the cam cover and the ignition module to the coil cassette.
A suspected ignition system misfire may actually be a condition other than the secondary ignition system. Verify proper operation of the following items:
• Fuel System
- Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 .
- Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95 Degrees F) .
- Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Outside 10-35 Degrees C (50-95 Degrees F) .
• Engine Mechanical Test for base engine conditions that could produce an engine misfire. Refer to Base Engine Misfire Diagnosis in Engine Mechanical 4.6L.
If the misfire is not present while operating the engine with the J 36012 spark plug jumper wires in place, and the misfire is present while the boots are installed, replace the affected boot.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
An ignition coil, boots or spark plugs may misfire only when moisture is present. Although difficult to test on this engine, selectively wetting down parts of the system and monitoring for misfire, may isolate an intermittent condition. If moisture is present in the spark plug/ignition coil cavity of the cam cover, inspect the perimeter seal for damage. Repair tears in the perimeter seal with RTV sealant.
The J 26792 spark tester (ST 125) places a higher load on the secondary ignition than a normal spark plug.
Use the correct adaptor harness when connecting the Ignition Module Tester. Using an adaptor harness for a different engine application will result in incorrect tool operation.
The green Power LED should come on any time the ignition module tester is connected and the ignition switch is in the run position. This LED indicates that the J 43298 is receiving adequate power and ground to perform the test. The Test button is used as an LED check for the four red LEDs. To use this function, connect the tool, turn the ignition switch to run, then momentarily press the Test button. All four red LEDs should come on brightly. Then crank the vehicle. If the four red LEDs flash, this confirms proper operation of the primary ignition system (PCM, wiring, connections, and ICM). The Ignition Module Tester may get hot during actual testing. This is because it is attempting to simulate the load of the ignition coils primary windings.
If the LEDs flash, the module output drivers are operating. If one or more LEDs are inoperative, and no individual IC Circuit (351-358), or IC Circuit Group (1359 and/or 1360) DTCs are set, replace the module.
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Last edited by AJxtcman; 07-07-07 at 02:51 PM.
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