P0742 on GMC
Torque Converter Clutch Circuit Stuck On
P0742 on GMC vehicles indicates torque converter clutch circuit stuck on. Au7o has documented this code across 5 GMC models — most commonly on C/K 1500, Sierra 1500, Sierra 2500HD. P0742 means the torque converter clutch (TCC) circuit is stuck on, meaning the lockup clutch that mechanically links the engine to the transmission stays engaged when it should release. The computer commands the clutch on and off, and when it detects the converter clutch remaining applied, it sets this code. The classic symptom is the engine stalling when coming to a stop, similar to driving a manual without pushing the clutch in, along with possible harsh shifts or poor fuel economy. It points to a hydraulic or solenoid problem inside the transmission rather than the engine. Typical repair costs on GMC range from $150 to $4,500, depending on the specific model and root cause.
Common Causes of P0742
- •Stuck or failed torque converter clutch solenoid
- •Stuck valve in the valve body (TCC apply valve)
- •Contaminated or degraded transmission fluid
- •Internal transmission hydraulic leak holding the clutch on
- •Wiring or connector fault to the TCC solenoid
- •Faulty torque converter
- •Dirty or clogged transmission filter
P0742 on GMC by Model
GMC C/K 1500(1 issue)
- 4L60E Automatic Transmission Failure1993-1998
Same 4L60E transmission issues as Chevrolet C/K. Sun shell failure, 3-4 clutch pack burnup, and worn input drum.
GMC Sierra 1500(1 issue)
- 8-Speed/10-Speed Transmission Torque Converter Shudder2015-2023
The 8L90 8-speed and 10L80/10L90 10-speed automatic transmissions experience shuddering during light throttle acceleration, particularly at highway speeds between 35-60 mph. The issue is caused by the torque converter lock-up clutch slipping and chattering. Harsh shifts between gears, especially 1st to 2nd and 2nd to 1st, are also commonly reported.
GMC Sierra 2500HD(1 issue)
- Allison 1000/2000 Transmission TCM Failure and Harsh Shifting2011-2025
The Allison 1000 (gas) and Allison 2000 (diesel) 6-speed automatic transmissions used in Sierra 2500HD/3500HD are widely regarded as extremely durable, but the Transmission Control Module (TCM) and solenoid pack do develop faults. Common issues include harsh 1-2 shifts, transmission sticking in one gear, slip codes, and the truck going into limp mode (3rd gear only). The Allison's proprietary Transynd fluid is critical — using non-approved fluid is the leading cause of premature solenoid wear. TCM software updates from GM address most calibration-related shift complaints.
GMC Sierra 3500HD(1 issue)
- Allison 1000/2000 Series Transmission Torque Converter Shudder2007-2020
The Allison 1000 and 2000 series automatic transmissions paired with Duramax engines in the Sierra 3500HD exhibit torque converter clutch shudder during light throttle cruising between 40–65 MPH as the TCC applies and releases. This is caused by degraded transmission fluid, worn TCC friction material, or contamination in the hydraulic circuit. GM and Allison have acknowledged this issue through multiple fluid specification updates and TSB 07-07-30-022.
GMC Yukon XL(1 issue)
- Transmission Torque Converter Shudder (8L90/10L80)2015-2024
The 8-speed (8L90) and 10-speed (10L80) automatic transmissions in the Yukon XL develop a torque converter clutch (TCC) shudder felt as a vibration or shake at light throttle between 25-50 mph. The shudder mimics driving over rumble strips. GM issued multiple TSBs (18-NA-355, 19-NA-193) and eventually reformulated the transmission fluid specification. The root cause is the TCC friction material interaction with the original Dexron HP fluid formulation.
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View P0742 across all makes →Frequently Asked Questions
What does P0742 mean on GMC?▼
P0742 stands for "Torque Converter Clutch Circuit Stuck On." P0742 means the torque converter clutch (TCC) circuit is stuck on, meaning the lockup clutch that mechanically links the engine to the transmission stays engaged when it should release. The computer commands the clutch on and off, and when it detects the converter clutch remaining applied, it sets this code. The classic symptom is the engine stalling when coming to a stop, similar to driving a manual without pushing the clutch in, along with possible harsh shifts or poor fuel economy. It points to a hydraulic or solenoid problem inside the transmission rather than the engine. On GMC specifically, this code is documented across 5 models.
What causes P0742 on GMC vehicles?▼
Common causes on GMC: Stuck or failed torque converter clutch solenoid, Stuck valve in the valve body (TCC apply valve), Contaminated or degraded transmission fluid, Internal transmission hydraulic leak holding the clutch on, Wiring or connector fault to the TCC solenoid. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0742 on a GMC?▼
Repair costs on GMC range from $150 to $4,500, depending on the specific model and root cause.
Which GMC models have P0742 documented?▼
Au7o has documented P0742 on 5 GMC models: C/K 1500, Sierra 1500, Sierra 2500HD, Sierra 3500HD, Yukon XL.