AutoCodes – GMC – P1258 2015 GMC Sierra

P1258 2015 GMC Sierra Code - Engine Coolant Overtemperature Protection Mode Active

Quick Answer

The Engine Control Module (ECM) uses the Engine Coolant Temperature (ECT) sensor to monitor the engine for an over-temperature condition. Common causes include Low Engine Coolant, Faulty Thermostat, Faulty Engine Coolant Temperature Sensor. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1258 2015 GMC Sierra indicates Engine Coolant Overtemperature Protection Mode Active.
Common causes: Common causes include Low Engine Coolant, Faulty Thermostat, Faulty Engine Coolant Temperature Sensor.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 225

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Aug 13, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P1258 2015 GMC Sierra Description

The Engine Control Module (ECM) uses the Engine Coolant Temperature (ECT) sensor to monitor the engine for an over-temperature condition. This condition occurs when the coolant temperature is above a calibrated value for a calibrated length of time. The ECM will disable half of the cylinders by turning OFF the fuel injectors. By disabling half of the cylinders, the ECM is able to reduce the temperature of the coolant. The Diagnostic Trouble Code (DTC) will be set when the coolant temperature is warmer than 129°C (264°F) for greater than 10 seconds.

OBDII Code P1258 2015 GMC Sierra - Engine Coolant Overtemperature Protection Mode Active - AutoCodes.com — P1258 2015 GMC Sierra Code - Engine Coolant Overtemperature Protection Mode Active

What does this mean?

What are the Possible Causes of the DTC P1258 2015 GMC Sierra?

Low Engine Coolant
Faulty Thermostat
Faulty Engine Coolant Temperature Sensor
Engine Coolant Temperature Sensor harness is open or shorted
Engine Coolant Temperature Sensor circuit poor electrical connection

How to Fix the DTC P1258 2015 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1258 2015 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P1258 2015 GMC Sierra code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.