Code PO128

2002 CHEVROLET IMPALA
120,000 MILES • 3.4L • 6 CYL • 4WD • AUTOMATIC
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CAT619
  • MEMBER
  • 1 POST
PO128. Low temperature. Slow heater. Bad has mileage. Bought new OEM thermostat with seal. Should I get a new gasket? What kind of sealant do I use?
Oct 8, 2019 at 10:30 PM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.
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SCGRANTURISMO
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 4,897 POSTS
Hello,

This DTC is not a problem with your vehicle's thermostat. If anything it is a problem with your vehicle's Engine Coolant Temperature Sensor [ECT]. In the diagrams down below I have included the vehicle manufacturers diagnostic troubleshooting flowchart for DTC P0128. Please go through this guide and get back to us with what you find out.

Thanks,
Alex
2CarPros
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Oct 8, 2019 at 10:41 PM
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