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 MANUALSCHEVROLET2019TAHOE LS, 4WD, GAS/ETHANOLREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 95 (ENGINE CONTROLS/FUEL - 1.8L (LUW LWE) - DTC P0010 TO DTC P0420)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P0128CIRCUIT/SYSTEM VERIFICATION
2019 Chevrolet Tahoe LS, 4WD, Gas/Ethanol
Circuit/System Verification
2019 Chevrolet Tahoe LS, 4WD, Gas/EthanolSECTION Circuit/System Verification
WARNING: This page is about a different car, the 2018 Chevrolet Sonic. However, it is still accessible from the selected car via links, so may be relevant.
- Verify the condition does not exist:Incorrect fluid level or condition - Refer to:Loss of Coolant
- If a condition exists
Repair or replace as necessary.
- Go to next step: If no condition exists
- If a condition exists
- Verify there are no DTCs set related to the following system/component:
- B34 Engine Coolant Temperature Sensor
- { If equipped }B203 Radiator Coolant Temperature Sensor
- { If equipped }E41 Engine Coolant Thermostat Heater
- { If equipped }Q74 Engine Coolant Bypass Valve
- If a related DTC is set
- Go to next step: If a related DTC is not set
- Perform the scan tool control function:Engine Coolant Thermostat Heater and Cooling Fan
- Engine Coolant Thermostat Heater - 100%
- Cooling Fan - 90%
- Engine Speed - 1, 800 to 2, 200 RPM
- Verify the scan tool parameter:ECT Sensor = Less than 85°C (185°F) - Within 5 min
- If 85°C (185°F) or warmer
Refer to:Circuit/System Testing
- Go to next step: If colder than 85°C (185°F)
- Perform the scan tool control function:Engine Coolant Thermostat Heater and Cooling Fan
- Engine Coolant Thermostat Heater - 0%
- Cooling Fan - 0%
- Engine Speed - 1, 800 to 2, 200 RPM
- Verify the scan tool parameter:ECT Sensor = Greater than 102°C (215°F) - Within 5 min
- If 102°C (215°F) or colder
Test or replace the component: E41 Engine Coolant Thermostat Heater
- Go to next step: If warmer than 102°C (215°F)
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Verify the DTC does not set.
- If the DTC sets
Refer to: Circuit/System Testing
- Go to next step: If the DTC does not set
- If the DTC sets
- All OK.
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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.