Electronic Ignition (EI) System Diagnosis LTD without Turbocharger
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 location in the spliced ignition voltage circuit, a slight resistance can cause a misfire or a crank/no start concern. A voltage drop test will pinpoint this condition. |
| • | A slight to moderate resistance on any IC circuit can cause a misfire before DTC P0351-P0354 sets. |
| • | Extended engine cranking time, may foul the spark plugs with excessive fuel. |
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 HEI Spark Tester
For equivalent regional tools, refer to
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 coil/modules are correctly connected |
| • | The proper firing order |
| • | The proper spark plug type |
| • | The proper spark plug gap and torque |
Circuit/System Testing
- Ignition OFF for 90 seconds, disconnect the harness connector at the affected T8 ignition coil/modules.
- Test for less than 5Ω 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 5Ω 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 K20 ECM. |
- Ignition ON, verify that a test lamp illuminates between the ignition 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 T8 ignition coil/module with the T8 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 T8 ignition coil/module, replace as needed. |
- If the circuits test normal, test or replace the spark plug/s.
Component Testing
Use the
J 26792 Spark Tester
to verify the output of each T8 ignition coil/module.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Electronic Ignition (EI) System Diagnosis LDK with Turbocharger
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
For equivalent regional tools, refer to
Special Tools.
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 for 90 seconds, disconnect the harness connector at the affected T8 ignition coil/modules.
- 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. |
- 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.
