Engine-Codes - Saturn - P0128 Saturn

P0128 Saturn Code - Engine Coolant Temperature Below Thermostat Regulating Temperature

- Code Popularity: 49,526 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 Saturn?

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 sensor
  • Engine coolant temperature sensor harness is open or shorted
  • Engine coolant temperature sensor circuit poor electrical 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 Saturn?

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 Saturn 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.

What are Code Possible Symptoms?

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

What Does the P0128 Saturn Code Mean?

The Engine Control Module (ECM) monitors the temperature of the engine coolant for engine control and as enabling criteria for some diagnostics. The amount of heat an engine generates is proportional to the amount of air that enters the engine. The ECM monitors this amount of air to calculate a theoretical Engine Coolant Temperature (ECT). The ECM uses the calculated temperature to determine if the engine has warmed up to the thermostat regulating temperature. Suppose the measured actual coolant temperature does not increase typically or does not reach the thermostat regulating temperature. In that case, diagnostics that use the ECT as enabling criteria, may not run when expected. If the measured engine coolant temperature fails to reach the thermostat regulating temperature, before a predetermined amount of air has entered the engine, this Diagnostic Trouble Code (DTC) sets.

P0128 Saturn Code - Engine Coolant Temperature Below Thermostat Regulating Temperature

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