Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2006COBALT SS, 4D SEDAN, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 706 (ENGINE CONTROLS AND FUEL - 2.0L - DTC P0010 TO DTC P0299)DTC P0128CIRCUIT/SYSTEM VERIFICATION
2006 Chevrolet Cobalt SS, 4D Sedan, Standard
Circuit/System Verification
2006 Chevrolet Cobalt SS, 4D Sedan, StandardSECTION Circuit/System Verification
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.
- Turn OFF the ignition.
- Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and Cooling System Draining and Filling (GE 47716 Fill) or Cooling System Draining and Filling (Static Fill LNF) .
- If the ignition has been OFF for 8 hours or greater, the IAT sensor, the IAT sensor 2 and the ECT sensor should be within 9°C (16°F) of each other and also the ambient temperature. Ignition ON, observe the scan tool IAT Sensor, IAT Sensor 2, and the ECT Sensor parameters. Compare those sensor parameters to each other and also to the ambient temperature to determine if the ECT sensor is skewed colder.
- Engine running, observe the ECT Sensor parameter. The reading should be between -39 to +120°C (-38 to +248°F) depending on the current ambient temperature and the vehicle operating conditions.
- Use the scan tool to verify the proper operation of the engine cooling system fans.
- Verify the proper heat range, and the operation of the thermostat. Refer to Thermostat Diagnosis .
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
IMPORTANT:
A critical analysis of the operation of the thermostat is necessary to properly diagnose this DTC.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.