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OBD code P0128

The engine takes too long to reach normal operating temperature or never reaches it.

Estimated severity
Low
Common symptoms
  • Temperature gauge takes a long time to rise or stays low
  • Fuel consumption slightly higher than normal
  • Cabin heating takes longer to warm up
Likely causes
  • Thermostat stuck open
  • Incorrect or poor-quality thermostat
  • Coolant temperature sensor giving an incorrect reading, less common
Recommended checks
  1. 1. Read coolant temperature with a scanner and compare it with the dashboard gauge.
  2. 2. Check warm-up time from a cold start.
  3. 3. If the engine remains cold while driving, replace the thermostat.

What does code P0128 mean?

P0128 means the engine does not reach operating temperature within the expected time. The most common cause is a thermostat stuck open or opening too early. Running the engine too cold increases fuel consumption, wear and emissions.

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