Diagnostic Instructions
Circuit/System Description
The ignition system uses individual ignition coil/module assemblies for each cylinder. The engine control module (ECM) controls the individual coils by transmitting timing pulses on the ignition control (IC) circuit of each ignition coil/module to enable
a spark event. Each ignition coil/module has the following circuits:
Diagnostic Aids
• | Depending on the location in the spliced ignition voltage circuit, a slight to moderate resistance can cause a misfire or a crank/no start concern. |
• | Extended engine cranking time, will foul the spark plugs with excessive fuel and cause a crank/no start condition. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
J 26792 Spark Tester
Circuit/System Verification
Note: Verify that the engine is in good mechanical condition before continuing with this diagnostic.
• | Review the ignition system specifications and the spark plug inspection procedure to verify the following: |
- | The ignition coil/modules are correctly connected |
- | The proper firing order |
- | The proper spark plug type |
- | The proper spark plug gap and torque |
• | If the engine will start, then observe the scan tool Misfire Current Cylinder parameters. This will indicate the affected ignition coil/modules. |
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the affected T8 ignition coil/modules.
- Ignition OFF for 90 seconds, test for less than 5Ω between the ground circuit terminal 1 and ground.
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
- Ignition OFF, test for less than 5Ω between the low reference circuit terminal 2 and ground.
⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM. |
- Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 4 and ground.
⇒ | If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. |
- Exchange the affected T8 ignition coil/module with the T8 ignition coil/module of a good cylinder.
- Start the engine, observe the scan tool Misfire Current Cylinder parameters.
⇒ | If the misfire transfers with the suspect T8 ignition coil/module, replace it. |
⇒ | If the misfire does not transfer with the suspect T8 ignition coil/module, replace the spark plug. |
Component Testing
Use the
J 26792 to verify the output of each ignition coil/module.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.