P0776 on GMC: How to Diagnose & Fix
Pressure Control Solenoid B Performance/Stuck Off
2 GMC models · 2 documented issues · 1 critical · $150-$4,500 repair
P0776 on GMC by model: symptoms, diagnosis and fix
The 2010-2017 Terrain uses the GM 6T45 (2.4L) and 6T70 (V6) 6-speed automatic transmissions, both of which suffer from torque converter shudder, harsh shifts, and solenoid failures. The shudder occurs at light throttle between 30-50 mph when the torque converter clutch locks up. Solenoid pack wear causes P0756, P0751, and P0776 transmission fault codes. The transmission is sensitive to fluid condition — the 6T45/6T70 was originally filled with Dexron VI, and that early fluid degrades faster than newer formulations, so a full fluid exchange with current Dexron VI is the first step.
Common Symptoms
- Shudder at light throttle 30-50 mph
- Harsh 1-2 or 2-3 upshift
- Hesitation or lurch when pulling away from a stop
- Transmission fault codes P0756, P0751, P0776
- Check engine light
- Delayed engagement from Park to Drive when hot
How to Fix
Full fluid exchange with Dexron VI (ACDelco 10-9243 or equivalent). TCM calibration update. Solenoid pack replacement (GM 24272814) if codes present. Valve body replacement for internal failures. Fluid service every 40,000 miles recommended for stop-and-go use.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Dexron VI full-synthetic automatic transmission fluidOEMACDelco 10-9243 (GM 88865549)Cross-refValvoline DEXRON VI ATF 822405, Mobil 1 Synthetic ATF Dexron VI 112980, Castrol Transmax DEXRON-VI 03520C$8–$15
Dexron VI is required — do NOT substitute Dexron III or a universal/multi-vehicle ATF, as the friction
- Control solenoid valve assembly (valve body + solenoids + TEHCM) — 2.4L, 2012-2013OEM24041960$600–$960
THIS is the part that actually fixes P0751/P0756/P0776 on the 6T40/6T45. GM does not sell the individual shift/pressure-control solenoids for this transmission as a serviceable part — the solenoids are integrated into the TEHCM/valve bod…
- Control solenoid valve assembly (valve body + solenoids + TEHCM) — 2.4L, 2014-2017OEM24041961$598–$915
Same function as 24041960 but the correct number for the later 2.4L Terrain — this is the year split, so do not cross-order between them.
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Sources for this issue (2)
The 35R clutch wave plate inside the 6T70/6T75 six-speed transaxle cracks and fractures, allowing the 35R clutch piston to overstroke and leak apply pressure. The result is a hard flare or slip in 3rd and 5th gear and eventually a complete loss of reverse. Failures typically begin after about 25,000 miles and are extremely common on the early Lambda Acadia; GM eventually extended coverage on the wave plate to 10 years/120,000 miles. Debris from the broken plate circulates through the transmission, so a simple plate swap is often not enough on high-mileage units.
Common Symptoms
- No reverse gear
- Slip or flare shifting into 3rd gear
- Harsh or delayed 3-5 shifts
- Check engine / SES light on
- RPM flares under acceleration then catches
How to Fix
Transmission must come apart. The correct repair is replacement of the 35R clutch wave plate with the redesigned/updated part plus new 35R clutch pack and seals, a thorough flush of the cooler and valve body, and a fluid/filter change. On units run for a long time after failure, a full rebuild or remanufactured transaxle is the realistic fix. GM Special Coverage 14404B (10 years/120,000 miles from the in-service date) has now expired on every 2007-2009 Acadia, but its parts list (3-5 reverse clutch backing plate, reverse clutch plates, seal kit) is a useful reference for the shop.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Sonnax 3-5-Reverse Drum Saver Kit (upgraded wave plate + cupped steel)Cross-refSonnax 124555K$55–$120
Fits Gen.1 and Gen.2 6T70/6T75 — the 2007-2012 Ac
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Sources for this issue (4)
- GM Special Coverage 14404B - Transmission Clutch Wave Plate (2007-2009 GMC Acadia)tsb
- WARNING 2007-2009 Acadia Owners - RE: 3-5-R Wave Plate Failure in Transmission — GMC Acadia Forumforum
- 2007-2009 Wave plate now has 10 yr/120,000 warranty! — GMC Acadia Forumforum
- Here's the Wave Plate - pictures — GMC Acadia Forumforum
P0776 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 P0776 mean on a GMC?
P0776 stands for "Pressure Control Solenoid B Performance/Stuck Off." This code means the transmission's Pressure Control Solenoid B is not performing correctly and is behaving as if stuck in the 'off' position. Pressure control solenoids regulate the hydraulic fluid pressure used to apply clutches and bands and to control shift quality, so when one underperforms the transmission may shift harshly, slip, flare between gears, or feel inconsistent. The transmission control module sets this code when the fluid pressure or response it measures doesn't match what it commanded from that solenoid. It generally indicates a hydraulic performance issue with the solenoid or its fluid circuit rather than just a wiring fault. On GMC it is documented across 2 models: Terrain, Acadia.
What are the most common causes of P0776?
The most common causes of P0776 are: Stuck or failed pressure control solenoid B, Low, dirty, or degraded transmission fluid, Clogged solenoid screen or valve body passages, Sticking or worn valve body components, Wiring or connector problem at the solenoid, Internal transmission wear or pressure loss, Faulty transmission control module. The specific cause varies by vehicle.
How much does it cost to fix P0776 on a GMC?
Published repair estimates on GMC range from $150 to $4,500 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.
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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.