Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
- Verify that the following conditions do not exist:
- Vacuum hose splits, kinks, and incorrect connections
- Engine vacuum leaks
- Crankcase ventilation system for vacuum leaks, refer to Crankcase Ventilation System Inspection/Diagnosis .
- Fuel pressure that is too low or too high, refer to Fuel System Diagnosis .
- Contaminated fuel, refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Restricted exhaust system, refer to Restricted Exhaust
.
- If you find any of the above conditions, repair as necessary.
- Ignition OFF, disconnect the harness connector at the appropriate Q17 Fuel Injector.
- Connect a test lamp between the control circuit terminal 2 and the ignition voltage circuit terminal 1.
- Engine idling, the test lamp should flash.
- If the test lamp does not flash, refer to DTC P0201-P0204 (LUW) .
- Ignition OFF, connect the Q17 Fuel Injector connector. Remove the T8 Ignition Coil.
- Inspect the ignition coil spark plug boots for the following conditions:
- Damage
- Carbon tracking
- Oil contamination
- Water intrusion
- If you find any of the above conditions, repair as necessary.
- Connect the harness connector to the ignition coil assembly.
- Install the EL 26792 HEI Spark Tester between the spark plug boot of the misfiring cylinder and ground.
- Connect the remaining wires to the appropriate cylinders.
- Attempt to start the engine and observe the EL 26792
HEI Spark Tester. The spark tester should spark.
- If there is no spark, refer to Electronic Ignition System Diagnosis .
- Ignition OFF, remove the spark plug from the misfiring cylinder. Verify the following conditions do not exist with the spark plug:
- Gas, coolant, or oil fouled, refer to Spark Plug Inspection .
- Cracked, worn, incorrectly gapped
- If there is a condition with the spark plug, replace the spark plug.
- Exchange the suspected spark plug with another cylinder that is operating correctly.
- Engine running, observe the scan tool Misfire Current Counters. The misfire should not follow the spark plug exchange.
- If the misfire follows the spark plug, replace the spark plug.
- If all conditions test normal, test or inspect for the following:
- A lean or rich fuel injector, refer to Fuel Injector Diagnosis .
- An engine mechanical condition, refer to Symptoms - Engine Mechanical .
NOTE:
An erratic or weak spark is considered a no spark condition.