Symptoms Testing

Test for the following conditions:
- The fuel system for the following:
  - Correct fuel pressure-Refer to Fuel System Diagnosis .
  - Fuel injectors that are leaking or improper operation. Refer to Fuel Injector Solenoid Coil Test .
  - Contaminated or a poor fuel quality condition-Refer to Alcohol/Contaminants-In-Fuel Diagnosis .
- The ignition system for the following:
  - Spark plugs for incorrect heat range or an abnormal condition
  - For diagnosis of coolant or oil fouled spark plugs-Refer to Loss of Coolant or Symptoms - Engine Mechanical .
  - Wet down the secondary ignition system with water from a spray bottle. Wetting down the secondary ignition system may help locate damaged or deteriorated components. Look/listen for arcing or misfiring as the water is applied.
  - Weak spark using the J 26792 Spark Tester-Refer to Electronic Ignition (EI) System Diagnosis .
- The operation of the transmission torque converter clutch (TCC)-The scan tool should indicate an engine speed drop when the TCC is commanded ON. Refer to Symptoms - Automatic Transmission for the Aisin (81-40LE) transmission or Symptoms - Automatic Transmission for the ZF 4HP 16 transmission.
- The operation of the A/C compressor
- Items that can cause an engine to run lean or rich-Refer to DTC P0171 or P0172 .
- The crankshaft position (CKP) sensor for the correct resistance-The CKP sensor resistance may be out of range after a hot soak. The resistance should be between 460-620 ohms.
- The engine for the following mechanical failures-Refer to Symptoms - Engine Mechanical :
  - Excessive oil in the combustion chamber or leaking valve seals
  - Incorrect cylinder compression
  - Sticking or leaking valves
  - Worn camshaft lobes
  - Incorrect valve timing
  - Worn rocker arms
  - Broken valve springs
  - Excessive carbon buildup in the combustion chambers-Clean the chambers with top engine cleaner. Follow the instructions on the can.
  - Incorrect engine parts
- Vacuum hoses for splits or kinks-Verify that the routing and connections are as shown on the Vehicle Emission Control Information label.
- Knock sensor (KS) system for excessive spark retard activity-Refer to Knock Sensor Replacement and DTC P0325 (European Emissions) or DTC P0325 (Non-European Emissions) .
- The exhaust system components for the following:
  - Physical damage or possible internal failure.
  - The three-way catalytic converters for a restriction.
    For more information, refer to Symptoms - Engine Exhaust .
- Electromagnetic interference (EMI) on the reference circuit can cause a misfire condition. You can usually detect EMI with a scan tool by monitoring the engine speed parameter. A sudden increase in the engine speed parameter with little change in actual engine speed indicates that EMI is present. Inspect the high voltage components near the ignition control circuit if a condition exists.
- The crankcase ventilation valve for proper operation
- Evaporative emission (EVAP) canister purge solenoid that is stuck open
- The engine cooling system for the following conditions:
  - The thermostat is the correct heat range-Refer to Thermostat Diagnosis .
  - Proper engine coolant level-Refer to Draining and Filling Cooling System .
If the above conditions do not address the symptom, refer to the additional symptoms tests.