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:
| • | An ignition 1 voltage circuit |
| • | A low reference circuit |
Diagnostic Aids
| • | This test procedure requires that the vehicle battery has passed a load test and is completely charged. |
| • | There is an adequate supply of fuel in the fuel tank. |
| • | 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
Description and Operation
Electronic Ignition (EI) System Description
Electrical Information Reference
Scan Tool Reference
Control Module References
Special Tools
J 26792
Spark Tester
Circuit/System Verification
Observe the Engine Controls Schematic for the ignition module/coils, and review the Ignition System Specifications to verify the following concerns:
| • | The ignition modules/coils are correctly wired and connected |
| • | The proper spark plug type |
| • | The proper spark plug gap and torque |
| • | The proper ohm values for the spark plug wires |
Circuit/System Testing
- Turn OFF the ignition.
Important: This engine application uses 2 fuses, one for each bank, to supply ignition 1 voltage to the ignition module/coil assemblies and also to the fuel injectors. A good indication that a fuse is open is that all 4 misfire
counters are incrementing on one side of the engine
- Inspect both fuse that supplies ignition voltage to the ignition module/coils.
| ⇒ | If a fuse is open, test all ignition voltage circuits to the ignition module/coils or the fuel injectors on the engine bank, for a short to ground. |
- Disconnect the ignition module/coil, and the fuel injector electrical connectors, for the engine bank that has the open fuse.
- Replace the open fuse with a new fuse.
- Ignition ON, engine OFF.
- Reconnect each ignition module/coil, and fuel injector electrical connectors, one at a time.
| ⇒ | If the fuse opens when connecting an ignition module/coil or fuel injector electrical connector, then replace the component that caused the fuse to open. |
- Ignition OFF, disconnect the appropriate ignition module/coil electrical connector.
- 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 voltage circuit for an open/high resistance. |
- Verify that a test lamp illuminates between the ignition module/coil ground circuit terminal A and B+.
| ⇒ | If the test lamp does not illuminate, test the ignition module/coil ground circuit for an open/high resistance. |
- Exchange the misfiring cylinder, ignition module/coil assembly with the ignition module/coil assembly from a non-misfiring cylinder.
Important: An open/high resistance on the low reference circuit to the IC module may cause a misfire.
- Start and idle the engine. Observe the misfire counters on the scan tool.
| ⇒ | If the misfire transfers with the suspect ignition module/coil, then replace the ignition module/coil assembly. |
| ⇒ | If the misfire does not transfer with the suspect ignition module/coil, then measure the resistance
of the IC circuit. The IC circuit should measure less than 5 ohms. If the circuit tests normal, replace the ECM. |
Component Testing
| • | Use the Spark Plug Inspection procedure to verify the integrity of the spark plugs. Refer to
Spark Plug Inspection. Replace the spark plug if necessary. |
| | Important: An erratic or weak spark is considered a no spark condition.
|
| • | Use the
J 26792
to verify the output of each ignition module/coil. If no spark is detected across the gap of the spark plug tester, then replace the ignition module/coil assembly. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
