P0125 – Meaning, Causes, Symptoms, & Fixes

Code P0125 Definition

Insufficient Coolant Temperature For Closed Loop Fuel Control

What Does P0125 Mean?

When this code is triggered, the Engine Control Module (ECM) has used its internal logic to determine that the engine hasn’t reached an operating temperature at the proper time. It does this by checking the Coolant Temperature Sensor value as the vehicle is warming up and comparing it to what it should be at certain times. If it seems that the vehicle’s coolant isn’t getting as warm as it should as fast as it should, it triggers this code.

What Are The Symptoms Of Code P0125?*

  • Check Engine Light
  • Poor fuel mileage
  • Temperature gauge reads cold all the time
  • Heat blows warm or cold when it should be hot

*No noticeable adverse conditions in some cases

What Is The Cause Of Code P0125?

  • Low engine coolant
  • Stuck open thermostat
  • Missing thermostat
  • Faulty coolant temperature sensor

How Serious Is Code P0125?- Low

This trouble code can present with no driveability concerns, but it can also cause the vehicle’s heat not to work and poor fuel economy. It should be fixed to get the vehicle back to optimum running conditions.  

Code P0125 Common Diagnosis Mistakes

Not checking the coolant level before replacing parts. 

Tools Needed to Diagnose:

  • FIXD
  • Basic Hand Tools
  • Vehicle Specific Service Manual

How To Diagnose And Repair Code P0125?

Difficulty of Diagnosis and Repair (2 out of 5)

  1. Check to see if there are any other codes along with P0125 and clear your Check Engine Light with FIXD.
  2. Check the freeze frame data in order to pinpoint the issue.
  3. Check coolant level; if it’s low, fill it up and bleed the air out of the system
  4. Check for Technical Service Bulletins (TSBs); there are some cars that have an ECM update for this code.
  5. Check the Coolant Temperature sensor voltage and compare it to your vehicle’s specific service manual. 
  6. If the Coolant Temperature Sensor passes this test, the thermostat is most likely stuck open or missing. Replace the thermostat, fill with new coolant, and bleed the coolant. 

Estimated Cost of Repair

For error code P0125, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. 

  • Thermostat $220-$260
  • Coolant Temperature Sensor $150-$200
  • Top off coolant $10

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