Diagnostic Instructions
Circuit/System Description
This ignition system uses individual ignition module/coil assemblies for each cylinder. The engine control module (ECM) controls the spark events by transmitting the timing pulses on the ignition control (IC) circuits to the individual ignition module/coil
assemblies in firing order sequence. Each ignition module/coil has the following circuits:
Diagnostic Aids
| • | Depending on location in the spliced ignition voltage circuit, a slight resistance can cause a misfire or a crank/no start condition. A voltage drop test on the circuit will pinpoint this condition. |
| • | A slight to moderate resistance on any IC circuit can cause a misfire before DTC P0351-P0358 sets. |
| • | Extended engine cranking time may foul the spark plugs with excessive fuel. |
| • | When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect both mating electrical terminals for corrosion and terminal tightness. |
| • | Use the
J 35616 for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness terminals. |
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
Circuit/System Verification
- Verify that the engine is in good mechanical condition before continuing with this diagnostic.
- Verify the following conditions:
| • | The ignition coils/modules are correctly wired and connected |
| • | The proper firing order |
| • | The proper spark plug type |
| • | The proper spark plug gap and torque |
| • | The proper ohm values for the spark plug wires |
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the affected ignition coil/modules.
- Ignition OFF for 90 seconds, test for less than 5 ohms between the ground circuit terminal A and ground.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
- Test for less than 5 ohms between the low reference circuit terminal B 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 ECM. |
Important: If the ignition fuse is open, it will be necessary to test the spliced ignition circuits and the components for a short to ground.
- Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal D and ground.
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
- Exchange the affected ignition coil/module with the ignition coil/module of a good cylinder.
- Start the engine and observe the scan tool Misfire Current Cylinder parameters.
| ⇒ | If the misfire transfers with the suspect ignition coil/module, replace as needed. |
- If the circuits test normal, test or replace the spark plugs.
Component Testing
Use the
J 26792 to verify the output of each ignition module/coil.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
