Electronic Ignition System Diagnosis
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Electronic Ignition System Diagnosis
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Circuit/System Description
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The ignition system on this engine uses individual ignition coils and ignition control circuits for each cylinder. Ignition voltage is supplied to each bank of ignition coils. The engine control module (ECM) controls the ignition system operation. The ECM controls each coil using the IC control circuits. The ECM commands the IC control circuit low when a spark event is requested. The sequencing and timing are controlled by the ECM.
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The ignition coils for each bank are fused separately. If a fuse opens or the ignition voltage circuit opens between the fuse and the splice, all the ignition coils for one bank of the engine would be inoperative. If the ground circuit opens at the engine block, the ignition coils would be inoperative for one bank of the engine.
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Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may cause a condition with the ignition coils.
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Schematic Reference
Engine Controls Schematics (3.0L (LF1))
Engine Controls Schematics (2.8L (LAU))
Connector End View Reference
Component Connector End Views
Description and Operation
Electronic Ignition System Description
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
Special Tools
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1.
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Note
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Do not perform this diagnostic procedure if you were not sent here from a misfire DTC or the Engine Cranks but Does Not Run diagnostic.
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Ignition OFF, disconnect the harness connector of the affected T8 ignition coil.
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2.
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Ignition ON, test for battery voltage between the ignition voltage circuit terminal D or 2 and ground.
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3.
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If less than B+, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all the components connected to the ignition voltage circuit and replace as necessary.
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4.
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Start the engine. Test for 200-400 mV between the appropriate ignition control circuit terminal C or 1 and ground.
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5.
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If less than the specified value, test the ignition control circuit for a short to ground or an open/high resistance. If the circuit/connection tests normal, replace the K20 ECM.
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6.
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If greater than the specified value, test the ignition control circuit for a short to voltage. If the circuit/connection tests normal, replace the K20 ECM.
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7.
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Ignition OFF, all vehicle systems OFF, this may take up to 2 min, test for less than 5 Ω between the low reference circuit terminal B or 3 and the K20 ECM housing.
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8.
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If greater than the specified value, test for an open/high resistance in the low reference circuit. If the circuit/connection tests normal, replace the K20 ECM.
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9.
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Test for less than 5 Ω between the ground circuit terminal A or 4 and ground.
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10.
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If greater than the specified value, test for an open, or high resistance in the ground circuit.
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11.
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Remove the T8 ignition coil from the engine. Connect the harness.
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12.
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Remove the fuse for the fuel pump or the fuel pump control module, if equipped.
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13.
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Crank the engine and test for strong spark using the
EL 26792
Tester.
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14.
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If no spark or weak spark is observed, replace the T8 ignition coil.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
