Circuit/System Testing
- Perform the Crankshaft Position System Variation Learn
procedure. Verify the scan tool displays Learned Successful.
- If the scan tool did not display Learned Successful
Inspect for the following conditions and repair as necessary:
- Worn crankshaft main bearings
- A damaged or misaligned reluctor wheel
- Excessive crankshaft runout
- Interference in the signal circuit of the crankshaft position sensor
- The ignition switch is in the ON position until there is insufficient system voltage.
- An ECM power disconnect with the ignition ON that may have erased the crankshaft position system variation values and set DTC P0315
- Debris between the crankshaft position sensor and the reluctor wheel
- If the engine control module is still unable to complete the learn procedure, replace the K20 Engine Control Module..
- If the scan tool displays Learned Successful
- If the scan tool did not display Learned Successful
- Verify that the following conditions do not exist:
- Vacuum hose splits, kinks, and incorrect connections
- Engine vacuum leaks
- Crankcase ventilation system for vacuum leaks
- Fuel pressure that is too low or too high-Refer to Fuel System Diagnosis .
- Contaminated fuel-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Exhaust system restrictions
- If a condition exist
Repair or replace as necessary.
- If no conditions exist
- If a condition exist
- Ignition OFF, remove the K35 Ignition Coil Module and connect the (EL 26792) HEI Spark Tester to the coil of the misfiring cylinder.
- Verify none of the conditions listed below exist with the boot of the K35 Ignition Coil Module:
- Holes
- Tears
- Carbon tracking
- Oil contamination
- Water intrusion
- If a condition exist
Repair or replace as necessary.
- If no conditions exist
- Verify the (EL 26792)
HEI Spark Tester sparks while cranking or starting the engine.
- If there is no spark
Refer to Electronic Ignition System Diagnosis for diagnosis of the ignition coil.
- If there is spark
- If there is no spark
- Ignition OFF, remove the spark plug from the misfiring cylinder.
- Exchange the suspected spark plug with another cylinder that is operating correctly.
- Engine idling.
- Verify the scan tool Cylinder 1-4 Current Misfire Counter parameter does not increment on the spark plug coil it was removed from.
- If the misfire does follow the spark plug exchange
Replace the spark plug.
- If the misfire does not follow the spark plug exchange
- If the misfire does follow the spark plug exchange
- Test or inspect for the following:
- A lean or rich Q17 Fuel Injector-Refer to Fuel System Diagnosis .
- An engine mechanical condition-Refer to Symptoms - Engine Mechanical .
NOTE:
An erratic or weak spark is considered a no spark condition.