Symptoms Testing

Cuts Out/Misses, Engine Control Module (ECM) Commanded Reduced Engine Power, Fuel Knock/Combustion Noise, Hard Start, Hesitation/Sag/Stumble, Lack of Power/Sluggishness/Sponginess, Poor Fuel Economy, Rough, Unstable, or Incorrect Idle and Stalling, Surges/Chuggles, or Excessive Smoke (Black), Excessive Smoke (White), Excessive Smoke (Gray or Blue)

1. Test for the following conditions:
   • The sensor systems for the following:
     • Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage.
     • Idle the engine and observe the Actual Fuel Rail Pressure and the Desired Fuel Rail Pressure parameters. If the pressure difference is more than 2 MPa, a fuel control issue may exist.
     • Inspect for the EGR valve sticking open. Command the valve to 20%. Desired and actual position should not be more than 3% different.
     • Inspect the CKP sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement, the reluctor wheel retaining bolts are loose.
     • Inspect the engine coolant temperature (ECT) sensor. Use the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, inspect for a high resistance in the coolant sensor circuit or the sensor itself.
     • Inspect for an intermittent Fuel Rail Pressure sensor signal by wiggling the harness between the sensor and the ECM with the ignition ON and the engine OFF, while monitoring the parameter with a scan tool.
     • Inspect for an intermittent crankshaft position (CKP) sensor signal. Refer to Testing for Intermittent Conditions and Poor Connections .
   • The Air Induction System for the following:
     • Leaks in the Induction system before the Turbocharger. Refer to Induction System Smoke Test in Charge Air Cooler Diagnosis .
     • Leaks in the Charge Air Cooler system. Refer to Charge Air Cooler Diagnosis .
     • Leaks in the engine assembly. Refer to Full System Air Leak Test in Charge Air Cooler Diagnosis .
   • The Fuel System for the following:
     • Inspect for external fuel leaks. Refer to Fuel Leak Diagnosis .
     • Inspect the fuel quality. Refer to Contaminants-in-Fuel Diagnosis , and Fuel System Specifications .
     • Inspect for the proper fuel pressure. Refer to Fuel System Diagnosis .
     • Inspect for proper fuel system return line pressure. Refer to Fuel Return System Diagnosis .
     • Inspect the engine speed signal circuit for high resistance.
     • If the ECM or a fuel injector has recently been replaced, it may be necessary to confirm the fuel injector flow rate values. Refer to Fuel Injector Flow Rate Programming .
     • Inspect the fuel tank cap vent for proper operation.
   • Engine mechanical for the following.
     • Improper valve timing
     • Low engine compression - Refer to Engine Compression Test .
     • Broken or weak valve springs
     • Worn camshaft lobes - Refer to Camshaft Housing Overhaul .
     • Excessive oil in the combustion chamber - Leaking valve seals - Refer to Oil Consumption Diagnosis .
2. If the above conditions do not address the symptom, refer to the additional symptoms tests.