AutoCodes – GMC – P0742 2018 GMC Sierra

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

Quick Answer

The Torque Converter Clutch (TCC) pressure control solenoid is part of the control solenoid valve assembly which has no serviceable parts. Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty Control Solenoid Valve Assembly. 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 Low transmission fluid level, Dirty transmission fluid, Faulty Control Solenoid Valve Assembly.
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 202

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 Jul 30, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P0742 2018 GMC Sierra Description

The Torque Converter Clutch (TCC) pressure control solenoid is part of the control solenoid valve assembly which has no serviceable parts. The TCC pressure control solenoid is a normally low-pressure control solenoid. The TCC pressure control solenoid regulates the transmission fluid to the TCC regulator valve in the lower valve body and the TCC control valve in the pump cover. When vehicle operating conditions are appropriate to apply the converter clutch, the Transmission Control Module (TCM) will increase TCC pressure control current flow (duty cycle) to the TCC solenoid. The TCC pressure control solenoid directs fluid pressure to move the TCC control valve to the apply position and moves the TCC regulator apply valve to the regulating position. The TCC regulator valve regulates TCC apply fluid pressure proportional to TCC solenoid pressure. When the TCC is fully applied, the engine is coupled directly to the transmission. TCC release is accomplished by the Transmission Control Module decreasing current flow to the TCC pressure control solenoid. This results in decreasing the applied pressure which allows the TCC control valve to move to the release position. The Transmission Control Module calculates torque converter slip speed based on engine speed and transmission input shaft speed.
The Diagnostic Trouble Code (DTC) will be set when the CM detects the TCC slip between −50 and +13 RPM for 6 s when the TCC is commanded OFF.

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

What does this mean?

What are the Possible Causes of the DTC P0742 2018 GMC Sierra?

Low transmission fluid level
Dirty transmission fluid
Faulty Control Solenoid Valve Assembly
Control Solenoid Valve Assembly harness is open or shorted
Control Solenoid Valve Assembly circuit poor electrical connection
Transmission internal mechanical problem

How to Fix the DTC P0742 2018 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 does this mean?

Code Tech Notes

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0742 2018 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.

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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.