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P1258 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P1258 is an OBD-II Code that refers to Engine Coolant Overtemperature Protection Mode Active


A P1258 code is caused by an ECM (Engine Control Module) receiving a signal from the PCM (Powertrain Control Module) that the engine is overheating. When this happens, the ECM will shut down the primary ignition system to prevent further damage. The protection mode is enabled and it sets a P1258 code when the engine coolant gets too hot.


Common causes for this code include:

  • Low engine coolant level or an empty radiator
  • Leaking or stuck open thermostat 
  • Plugged radiator
  • Faulty Engine Coolant Temperature Sensor 
  • Engine Coolant Temperature Sensor Bad Connection
  • Bad Circuit


The symptoms of a P1258 code are:

  • The Check Engine Light comes on 
  • Engine overheats 
  • The vehicle eventually stalls and will not start


To diagnose a P1258 DTC code, a technician would:

  1. Scan for codes 
  2. Inspect for coolant leaks, coolant level and condition 
  3. Check the thermostat for proper operation 
  4. Inspect cooling system components 
  5. Inspect the radiator and hoses for obstructions 

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P1258 code:

  • Not checking for a sufficient amount of coolant in the system 
  • Not replacing the thermostat if it is suspected that it is faulty
  • Clearing the code without fully diagnosing the code
  • Not checking for corrosion or loose connections in the coolant temperature sensor circuit
  • Replacing parts that are not faulty when detecting intermittent problems 
  • Not following proper diagnostic procedures
  • Overlooking simple fixes to more complex issues.  

How serious is this?

A P1258 code is serious and should be taken seriously as the problem will only get worse if left unrepaired. If a vehicle is rapidly overheating it could lead to engine damage such as warped cylinder heads and blown head gaskets. The driver should pull over and shut off the engine as soon as safely possible and contact a service provider immediately.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Visually inspect for low coolant levels or an empty radiator
  • Replace the thermostat 
  • Check the coolant temperature sensor for proper connection and operation
  • Repair any leaks in the cooling system components 
  • Clean out any obstructions in the cooling system hoses 
  • Inspect wiring connections to connectors in the cooling system circuit. If needed, replace connectors that are corroded or faulty.  

Related codes

A P1258 is related to and may be accompanied by the following codes:

P0128 – Engine Coolant Overtemperature Condition

P0300 – Random/Multiple Cylinder Misfire Detected

P1260 – Engine Oil Temperature Sensor Malfunction

P1278 – Cooling System Performance Problem


Though a P0422 trouble code may not be immediately detrimental to your vehicle, it is something that should be investigated and fixed as soon as possible. If the problem is properly diagnosed and investigated, it is something that can be fixed fairly easily.