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P0126

Overview

Code

P0126

Code Type

P

Code Class

P0

System

Engine

Severity Level

Low

Emissions Related

true

Drivability Impact

Minor

Diagnostic Protocol

OBD2

Freeze Frame Useful

true

Code Definition

Diagnostic trouble code P0126 indicates insufficient coolant temperature for stable engine operation detected by the ECM

Symptoms

Check Engine Light illuminated; Poor fuel economy; Delayed heater performance

Overview applies to this diagnostic code.

Affected Systems

On This Page

  • Code Definition

  • Symptoms

  • Affected Systems

  • Possible Causes

  • Diagnostic Steps

  • Drive Safety Notes​

More Resources

Engine warm-up and fuel management systems rely on proper coolant temperature

Possible Causes

Thermostat stuck open; Faulty ECT sensor; Cooling system issues

Diagnostic Steps

1 Confirm the code; 2 Monitor coolant temperature rise; 3 Inspect thermostat function; 4 Check coolant level and flow; 5 Replace faulty components as needed

Drive Safety Notes

Driving is generally safe, but extended operation may affect fuel efficiency

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