Engine-Codes - Generic - P0128

P0128 Code - Coolant Thermostat Malfunction

- Code Popularity: 283,812 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 2/3
Table of contents
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What are the Possible Causes of the DTC P0128?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Leaking or stuck open thermostat
  • Low engine coolant level
  • Insufficient warm-up time
  • Faulty Engine Coolant Temperature (ECT) sensor
  • Engine Coolant Temperature sensor harness is open or shorted
  • Engine Coolant Temperature sensor electrical circuit poor connection

Code Tech Notes

If the cooling system is not leaking and the fluid level is OK, replacing the thermostat usually takes care of the problem.









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How to Fix the DTC P0128?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

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What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P0128 code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

When is the Code Detected?

The engine coolant temperature does not reach to specified temperature even though the engine has run long enough.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

What Does the P0128 Code Mean?

The thermostat is a component that blocks the flow of coolant to the radiator until the engine has warmed up. When the engine is cold, no coolant flows through the engine. Once the engine reaches its operating temperature, the thermostat opens. The OBDII sets when the engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough. This is due to a leak in the seal, or the thermostat open stuck.

P0128 Code - Coolant Thermostat Malfunction

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Code P0128 Information for Specific Makes

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