Electronic Ignition (EI) System Diagnosis with LY7
Diagnostic Instructions
Circuit/System Description
The ignition system on this engine uses individual ignition coils and ignition control (IC) 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 circuits. The ECM commands the IC circuit low when a spark event is requested. The sequencing and timing are controlled by the ECM.
Diagnostic Aids
| • | 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. |
| • | Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may cause a condition with the ignition coils. |
Reference Information
Schematic Reference
Engine Controls Schematics
Description and Operation
Electronic Ignition (EI) System Description
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
Circuit/System Testing
Note: 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.
- Ignition OFF, disconnect the harness connector of the ignition coil.
- Ignition ON, load test for battery voltage between the ignition voltage circuit terminal D and ground.
| ⇒ | 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. |
- Crank or start the engine. Test for 200-400 mV between the appropriate IC circuit terminal C and ground.
| ⇒ | If less than the specified value, test the IC circuit for a short to ground or an open/high resistance. If the circuit/connection tests normal, replace the ECM. |
| ⇒ | If greater than the specified value, test the IC circuit for a short to voltage. If the circuit/connection tests normal, replace the ECM. |
- Ignition OFF, connect a test lamp between the low reference circuit terminal B and B+. The test lamp should illuminate.
| ⇒ | If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuit/connection tests normal, replace the ECM. |
- Connect a test lamp between the ground circuit terminal A and B+. The test lamp should illuminate.
| ⇒ | If the test lamp does not illuminate, test the circuit for an open/high resistance. |
- If all circuits/connections test normal, replace the ignition coil.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Electronic Ignition (EI) System Diagnosis with LLT
Diagnostic Instructions
Circuit/System Description
The ignition system on this engine uses individual ignition coils and ignition control (IC) 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 circuits. The ECM commands the IC circuit low when a spark event is requested. The sequencing and timing are controlled by the ECM.
Diagnostic Aids
| • | 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. |
| • | Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may cause a condition with the ignition coils. |
Reference Information
Schematic Reference
Engine Controls Schematics
Description and Operation
Electronic Ignition (EI) System Description
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
Circuit/System Testing
Note: 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.
- Ignition OFF, disconnect the harness connector of the ignition coil.
- Ignition ON, load test for battery voltage between the ignition voltage circuit terminal 2 and ground.
| ⇒ | 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. |
- Crank or start the engine. Test for 200-400 mV between the appropriate IC circuit terminal 1 and ground.
| ⇒ | If less than the specified value, test the IC circuit for a short to ground or an open/high resistance. If the circuit/connection tests normal, replace the ECM. |
| ⇒ | If greater than the specified value, test the IC circuit for a short to voltage. If the circuit/connection tests normal, replace the ECM. |
- Connect a test lamp between the each of the ground circuits terminal 3, and terminal 4, and B+. The test lamp should illuminate on each circuit.
| ⇒ | If the test lamp does not illuminate, test the suspected circuit for an open/high resistance. |
- If all circuits/connections test normal, replace the ignition coil.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
