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Engine-Codes – GMC – P0742 2018 GMC Sierra

P0742 2018 GMC Sierra Code - Torque Converter Clutch System Stuck On Or Transmission Hydraulic/Mechanical Performance

Quick Answer

The P0742 diagnostic trouble code (DTC) for a 2018 GMC Sierra relates to the Torque Converter Clutch (TCC) system being stuck on or experiencing transmission hydraulic/mechanical performance issues. Common causes include Faulty TCC solenoid, Malfunctioning torque converter, Low transmission fluid levels. 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
P0742 2018 GMC Sierra indicates Torque Converter Clutch System Stuck On Or Transmission Hydraulic/Mechanical Performance.
Common causes
Common causes include Faulty TCC solenoid, Malfunctioning torque converter, Low transmission fluid levels.
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 17, 2024
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Code P0742 2018 GMC Sierra Description

The P0742 diagnostic trouble code (DTC) for a 2018 GMC Sierra relates to the Torque Converter Clutch (TCC) system being stuck on or experiencing transmission hydraulic/mechanical performance issues. The TCC is a component of the automatic transmission that helps improve fuel efficiency by locking the torque converter when cruising at highway speeds. When the TCC is stuck on or not functioning properly, it can lead to various issues with the transmission's operation.

OBDII Code P0742 2018 GMC Sierra - Torque Converter Clutch System Stuck On Or Transmission Hydraulic/Mechanical Performance
P0742 2018 GMC Sierra Code - Torque Converter Clutch System Stuck On Or Transmission Hydraulic/Mechanical Performance

Common Causes of P0742 2018 GMC Sierra

  1. Faulty TCC solenoid
  2. Malfunctioning torque converter
  3. Low transmission fluid levels
  4. Clogged transmission filter
  5. Internal transmission damage

Symptoms of P0742 2018 GMC Sierra

  1. Harsh shifting
  2. Reduced fuel efficiency
  3. Transmission slipping
  4. Overheating
  5. Stalling

How to Fix P0742 2018 GMC Sierra

  1. Diagnose the specific cause of the issue using a scan tool to pinpoint the exact problem.
  2. Inspect the TCC solenoid and torque converter for any signs of damage or wear.
  3. Check the transmission fluid level and condition, topping off or replacing as necessary.
  4. Replace the TCC solenoid or torque converter if found to be faulty.
  5. Clear the DTC and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0742 2018 GMC Sierra

The cost of repairing a P0742 code on a 2018 GMC Sierra can vary depending on the specific cause of the issue and the labor rates in your area. On average, the repair costs for this type of transmission issue can range from $300 to $800, including parts and labor. It's important to note that diagnostic time and labor rates at auto repair shops can fluctuate, so it's advisable to obtain quotes from multiple sources to get an accurate estimate.

What does this mean?

Tech Notes for P0742 2018 GMC Sierra

When a transmission solenoid is stuck on, in most cases the problem is not the electrical part of the solenoid; the problem is foreign material obstructing the mechanical function of the solenoid or the flow of the fluid through the transmission valve body. If the transmission fluid is very dirty, it is recommended to change the transmission fluid and if possible, remove the transmission pan for further diagnosis. Excessive debris or metal particles on the transmission pan could be an indication that there is a transmission mechanical failure, and that the transmission will need to be rebuilt or replaced.

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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.

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