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Engine-Codes – GMC – P242C 2018 GMC Sierra

P242C 2018 GMC Sierra Code - Exhaust Gas Temperature Sensor 3 Circuit Low Voltage

Quick Answer

The P242C diagnostic trouble code (DTC) for a 2018 GMC Sierra indicates a problem with the Exhaust Gas Temperature Sensor 3 Circuit, specifically a low voltage condition. Common causes include Faulty Exhaust Gas Temperature Sensor 3, Wiring or connector issues in the sensor circuit, Corrosion or damage to the sensor components. 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
P242C 2018 GMC Sierra indicates Exhaust Gas Temperature Sensor 3 Circuit Low Voltage.
Common causes
Common causes include Faulty Exhaust Gas Temperature Sensor 3, Wiring or connector issues in the sensor circuit, Corrosion or damage to the sensor components.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 18, 2024
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Code P242C 2018 GMC Sierra Description

The P242C diagnostic trouble code (DTC) for a 2018 GMC Sierra indicates a problem with the Exhaust Gas Temperature Sensor 3 Circuit, specifically a low voltage condition. This sensor is responsible for monitoring the exhaust gas temperature and providing this data to the engine control module (ECM) to ensure optimal fuel efficiency and emissions control. When the voltage from the sensor is lower than expected, it can lead to various issues with the vehicle's performance.

OBDII Code P242C 2018 GMC Sierra - Exhaust Gas Temperature Sensor 3 Circuit Low Voltage
P242C 2018 GMC Sierra Code - Exhaust Gas Temperature Sensor 3 Circuit Low Voltage

Common Causes of P242C 2018 GMC Sierra

  1. Faulty Exhaust Gas Temperature Sensor 3.
  2. Wiring or connector issues in the sensor circuit.
  3. Corrosion or damage to the sensor components.
  4. ECM software or hardware problems.
  5. Exhaust system leaks or restrictions affecting sensor readings.

Symptoms of P242C 2018 GMC Sierra

  1. Check engine light illuminated on the dashboard.
  2. Reduced fuel efficiency.
  3. Increased emissions.
  4. Engine performance issues, such as rough idling or hesitation.
  5. Potential damage to the engine or catalytic converter if left unresolved.

How to Fix P242C 2018 GMC Sierra

  1. Use a scan tool to read and document the P242C DTC.
  2. Inspect the Exhaust Gas Temperature Sensor 3 and its wiring for any visible damage or corrosion.
  3. Test the sensor's resistance values and voltage output to determine if it is functioning correctly.
  4. Replace the sensor if it is found to be faulty, ensuring proper installation and connection.
  5. Clear the DTC from the ECM and perform a test drive to verify that the issue has been resolved.

Cost to Fix P242C 2018 GMC Sierra

The typical repair costs for addressing a P242C DTC on a 2018 GMC Sierra can vary depending on the specific cause of the issue and the labor rates in your area. In general, replacing the Exhaust Gas Temperature Sensor 3 and addressing any related wiring or connector issues may cost between $200 and $500, including parts and labor. Keep in mind that diagnostic time and labor rates at auto repair shops can fluctuate, so it's advisable to obtain quotes from multiple sources to ensure a competitive price.

What does this mean?

Tech Notes for P242C 2018 GMC Sierra

After starting the engine, the exhaust gas temperature sensor temperature should rise steadily, then stabilize after the engine reaches operating temperature. Exhaust gas temperature sensors may fail intermittently while operating under extreme temperatures. Review the Freeze Frame/Failure Records to verify the failure criteria.

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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.

Frequently Asked Questions about P242C 2018 GMC Sierra Code

1. What does the OBDII code P242C mean on a 2018 GMC Sierra?

P242C indicates that the powertrain control module (PCM) has detected a low voltage signal from Exhaust Gas Temperature Sensor 3, which monitors exhaust temperatures to optimize emissions and engine performance.

2. What are the common symptoms of the P242C code on a 2018 GMC Sierra?

Symptoms may include the check engine light turning on, decreased fuel efficiency, poor engine performance, and in some cases, the vehicle entering limp mode.

3. What causes the P242C code to appear on a 2018 GMC Sierra?

Common causes include a faulty exhaust gas temperature sensor, damaged wiring or connectors, excessive soot buildup on the sensor, or issues with the PCM.

4. Can I drive my 2018 GMC Sierra with the P242C code?

While the vehicle may still be drivable, continuing to drive with this code could lead to increased emissions, engine performance issues, or potential damage to the exhaust system.

5. How is the P242C code diagnosed on a 2018 GMC Sierra?

A technician will use an OBDII scanner to confirm the code, inspect the exhaust gas temperature sensor and its wiring for damage, and test the sensor's voltage output to determine if it’s functioning correctly.

6. How do I fix the P242C code on a 2018 GMC Sierra?

Repairs may include replacing the faulty exhaust gas temperature sensor, repairing or replacing damaged wiring, cleaning soot buildup from the sensor, or updating/reprogramming the PCM if needed.

7. How much does it cost to repair the P242C code on a 2018 GMC Sierra?

The cost can vary depending on the issue, but replacing an exhaust gas temperature sensor typically ranges from $100 to $300, including parts and labor.

8. What tools are needed to repair the P242C code on a 2018 GMC Sierra?

Common tools include an OBDII scanner, multimeter for testing voltage, and basic hand tools for sensor removal and installation.

9. Can a dirty exhaust gas temperature sensor cause the P242C code?

Yes, excessive soot or carbon buildup on the sensor can interfere with its operation and trigger the code.

10. Is it necessary to clear the P242C code after repairs?

Yes, after repairs are completed, the code should be cleared using an OBDII scanner, and the vehicle should be test-driven to ensure the issue is resolved.

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