P0743 on GMC: How to Diagnose & Fix
Torque Converter Clutch Circuit Electrical
1 GMC model · 1 documented issue · $150-$2,200 repair
P0743 on GMC by model: symptoms, diagnosis and fix
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.
Common Symptoms
- Vibration or shudder between 40–65 MPH at light throttle
- Shudder disappears under hard acceleration or deceleration
- Transmission hesitation or clunk when TCC engages
- Rough or inconsistent lockup feel during highway cruising
- Transmission fluid with burnt smell or dark discoloration
How to Fix
Drain and refill with Allison-approved TES-295 or TES-468 fluid (Transynd or equivalent); do not use generic ATF. If shudder persists after fluid service, a complete torque converter replacement (remanufactured unit $400–$800) and valve body cleaning is required. GM TSB 07-07-30-022 outlines the fluid change procedure and updated fill volume specifications. Complete transmission fluid flush recommended every 50,000 miles for prevention.
Sources for this issue (1)
P0743 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 P0743 mean on a GMC?
P0743 stands for "Torque Converter Clutch Circuit Electrical." This code indicates an electrical fault in the torque converter clutch (TCC) circuit, the wiring and solenoid that lock the torque converter so the engine and transmission turn together for better efficiency at cruising speed. The transmission computer commands the TCC solenoid on and off, and when it sees an open, short, or out-of-range electrical signal in that circuit, it sets this code. You may notice slipping, harsh or no lockup, reduced fuel economy, or the transmission staying in a lower gear. Because it is an electrical-circuit code, the problem is usually in the solenoid, connector, or wiring rather than worn mechanical clutch material. On GMC it is documented across 1 model: Sierra 3500HD.
What are the most common causes of P0743?
The most common causes of P0743 are: Failed torque converter clutch (TCC) solenoid, Open, shorted, or corroded wiring in the TCC circuit, Damaged or loose transmission connector, Low or contaminated/dirty transmission fluid, Faulty transmission valve body or internal harness, Failed torque converter (internal clutch), Faulty transmission control module (TCM/PCM). The specific cause varies by vehicle.
How much does it cost to fix P0743 on a GMC?
Published repair estimates on GMC range from $150 to $2,200 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0743 on a different make?
View P0743 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.