Ignition System: Testing and Inspection
Electronic Ignition System Diagnosis
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
This ignition system uses an individual ignition coil 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 coil in firing order sequence. Each ignition coil has the following circuits:
* An ignition 1 voltage circuit
* A ground circuit
* An IC circuit
* A low reference circuit
Diagnostic Aids
* This engine application may use 2 fuses, one for each bank, to supply ignition voltage to the ignition module/coil assemblies and also to the fuel injectors. A good indication that a fuse is open is that all misfire counters are incrementing on one side of the engine.
* An open/high resistance on the low reference circuit to the ignition coil may cause a misfire.
* An erratic or weak spark is considered a no spark condition.
Reference Information
Schematic Reference
Engine Controls Schematics (LFX) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Electronic Ignition System Description Electronic Ignition System Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References
Special Tools
EL 26792 - Spark Tester
Circuit/System Testing
Note: Do not perform this diagnostic procedure unless you were sent here from a misfire DTC or the Engine Cranks But Does Not Run diagnostic.
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate T8 Ignition Coil. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 ohms between the ground circuit terminal A and ground.
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Test for less than 5 ohms between the low reference circuit terminal B and ground.
• If 5 ohms or greater
1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
2. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If less than 5 ohms
4. Ignition ON.
5. Verify a test lamp illuminates between the ignition circuit terminal D and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the ignition circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF, disconnect all T 8 Ignition Coils.
2. Test for infinite resistance between the ignition circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Replace the fuse, ignition ON
4. Verify the fuse is good after connecting each T 8 Ignition Coil one at a time.
• If the fuse opens, replace the T 8 Ignition Coil that opens the fuse when connected.
• If the fuse is good, replace the K20 Engine Control Module.
• If the test lamp illuminates
6. Ignition OFF, exchange the suspect T8 Ignition Coil with the T8 Ignition Coil of a known functioning cylinder.
7. Engine running.
8. Verify the scan tool Ignition Coil Control Circuit Status parameter displays OK for the same cylinder that the suspect T8 Ignition Coil was removed from.
• If OK is not displayed
Replace the K20 Engine Control Module.
• If OK is displayed
Test or replace the suspect T8 Ignition Coil.
Component Testing
Note: You must perform the Circuit/System Testing before proceeding with Component Testing.
1. Ignition OFF, connect the EL 26792 - spark tester to the appropriate T8 Ignition Coil.
2. Engine running.
3. Verify the spark output of the T8 Ignition Coil.
• If no output or the output is weak
Replace the T8 Ignition Coil
• If the output is good
4. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Ignition Coil Replacement - Bank 1 Ignition Coil Replacement - Bank 1
* Ignition Coil Replacement - Bank 2 Ignition Coil Replacement - Bank 2
* Control Module References Control Module References for engine control module replacement, programming, and setup.