Circuit/System Testing
WARNING: This page is about a different car, the 2008 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
Allow the engine to reach operating temperature. With the engine idling, observe the Long Term FT parameter with a scan tool. The value should be less than approximately 20 percent with the engine running at operating temperature.
- If the value is greater than 20 percent, inspect for the following:
- With the ignition ON and the engine OFF, observe the manifold absolute pressure (MAP) sensor parameter. The MAP sensor pressure should be within the range specified for your altitude. Refer to Altitude Versus Barometric Pressure
.
- If the MAP sensor does not indicate the correct barometric pressure, refer to DTC P0106 or DTC P0107 or P0108 .
- With the engine idling, observe the mass air flow (MAF) sensor parameter. The MAF sensor parameter should be between 2-6 g/s at idle.
- If the MAF sensor parameter is not between 2-6 g/s at idle, refer to DTC P0100, P0102, or P0103 or DTC P0101 .
- Vacuum hoses for splits, kinks, and improper connections
- Insufficient fuel in the tank
- Low fuel pressure-Refer to Fuel System Diagnosis .
- Ethanol concentration greater than 15 percent-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Malfunctioning fuel injectors
- Missing, loose, or leaking exhaust components from the HO2S forward-Refer to Symptoms - Engine Exhaust .
- Vacuum leaks at the intake manifold and the throttle body
- Vacuum leaks at the charge air bypass valve solenoid, the charge air bypass valve, and the charge air bypass valve vacuum tank.
- The air induction system and the air intake ducts for leaks or for a missing air filter element
- A cracked EVAP canister
- Evaporative pipes obstructed or leaking
- The crankcase ventilation system for leaks-Refer to Crankcase Ventilation System Inspection/Diagnosis .
- The HO2S for improper installation and for electrical wires or connectors that may have suffered corrosion, water intrusion, or contacted the exhaust system
- Incorrect terminal tension at electrical connectors
- Loose, corroded, or mislocated electrical ground connections
- The HO2S signal circuit open, shorted to ground, or shorted to the low reference circuit
- Malfunctioning engine components-Refer to Symptoms - Engine Mechanical .