P0742 on Cadillac: How to Diagnose & Fix
Torque Converter Clutch Circuit Stuck On
1 Cadillac model · 1 documented issue
P0742 on Cadillac by model: symptoms, diagnosis and fix
The CT5 uses GM's 10-speed automatic (10L80) that can exhibit harsh shifts, delayed engagement, and shift hunting, particularly when the adaptive learning resets. The 10-speed has very complex shift logic and can take 500+ miles to fully adapt to a driver's pattern after a battery disconnect, TCM update, or reset. Some CT5 owners report persistent shift quality issues even after adaptation. The CT5-V and CT5-V Blackwing have refined calibrations but can still exhibit occasional harsh shifts.
Common Symptoms
- Harsh 1-2 or 3-4 shifts
- Delayed shift from Park to Drive/Reverse
- Transmission hunting between gears on hills
- Shift quality changes after battery disconnect or service
- Clunky low-speed maneuvers
How to Fix
Have dealer perform latest TCM software calibration - GM releases regular updates. Allow 500+ miles after any reset for the transmission to relearn. For persistent issues, a full transmission fluid exchange with Mobil 1 LV ATF HP can improve shift quality. Very few CT5s require hardware repair.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (1)
P0742 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0742 mean on a Cadillac?
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 Cadillac it is documented across 1 model: CT5.
What are the most common causes of P0742?
The most common causes of P0742 are: 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. The specific cause varies by vehicle.
How much does it cost to fix P0742 on a Cadillac?
Repair costs vary widely with the root cause and Cadillac model; each issue on this page carries its own estimate where one is published.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.