Circuit/System Testing

If any DTCs other than DTC P0300, P0301-P0308 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

1. Start and run the engine until the ECT is more than 82°C (180°F).
2. Turn OFF all accessories.
3. Perform the fuel pressure regulator test. Refer to Fuel Pressure Regulator Diagnosis .
   • If the fuel pressure regulator graph was not normal, replace the fuel pressure regulator Fuel Pressure Regulator Replacement .
4. Place the transmission in Neutral and apply the parking brake.
5. Hold the brake pedal in the fully applied position. A hiss will be noticeable when the brake is fully applied.
6. Idle the engine for more than 30 seconds.
7. Record the Balancing Rate Cyl.1-8 parameters from the scan tool while the engine is at idle speed.
   • If at least 5 of the Balancing Rates are more than +4 mm³ , refer to Engine Flywheel Replacement (Automatic Transmission) or Engine Flywheel Replacement (Manual Transmission) .
   • If the Balance Rates are not between +4 mm³ and -4 mm³ at idle, perform the Cylinder Power Balance Test in Special Functions.
IMPORTANT: The Cylinder Power Balance Test must be performed under the conditions for which the concern occurred. The concern must be duplicated during the test.
8. Record any cylinders that indicate a different cylinder power contribution and compare the Balance Rates previously recorded with the Cylinder Power Balance results.
   • If the Balance Rates were not high or the Cylinder Power Balance test did not indicate a cylinder with a different power contribution, refer to Diagnostic Aids .
IMPORTANT: A fuel injector leak into the combustion chamber may result in mechanical damage to the cylinder. If any fuel spray comes out of a glow plug hole during the compression test, replace the fuel injector of the affected cylinder.
9. Perform the engine compression test. Refer to Engine Compression Test .
   • If the compression test indicated any of the cylinder had low compression, refer to Symptoms - Engine Mechanical .
IMPORTANT: Refer to Injection System Components in Engine Controls Component Views . Failure to correctly identify the cylinder positions may result in the replacement of the wrong fuel injector.
IMPORTANT: During replacement of the injectors, inspect the inlet and outlet fittings of the injectors for corrosion or contamination. Refer to Contaminants-in-Fuel Diagnosis .
10. If the engine did not have low compression on any of the cylinders, replace the fuel injectors on the cylinders that had poor cylinder power contribution, high balance rates, or a noise/smoke change during cancellation. Refer to Fuel Injector Replacement (Left) or Fuel Injector Replacement (Right) .
11. Operate the vehicle under the conditions in which the concern occurred.