P0776 Code: Pressure Control Solenoid B Stuck Off (GM 6L80/8L90)

P0776 is "Pressure Control Solenoid B Performance or Stuck Off" in generic SAE terms, but on GM's 6L80 and 8L90 it points at two completely different clutches. On the 6L80 and 6L90, GM calls it Clutch Pressure Control Solenoid 2 Stuck Off, and that solenoid runs the 3-5-Reverse clutch. On the 8L90 and 8L45, GM's tables list it as Pressure Control Solenoid B Stuck Off for clutch 2, the CB12345R clutch. In both cases "stuck off" means the same thing to the transmission module: the clutch was commanded on and did not hold. On the 6L80 there is a well-documented cause that is not the solenoid at all.

What Does P0776 Mean on a GM Truck?

Every clutch in a 6L80 or 8L90 is applied by a variable pressure control solenoid. The transmission control module sets exactly how much pressure each clutch gets, gear by gear and shift by shift. P0776 means the module commanded pressure to the clutch run by solenoid "B" (GM's solenoid 2), and the speed sensors showed slip, as if that clutch was not applied.

"Stuck off" is the module's conclusion, not a diagnosis. It cannot see inside the transmission. It only knows that the clutch it asked for is not holding. That could be:

• the solenoid not producing pressure (electrical or mechanical failure of the solenoid),
• the regulator valve downstream of it sticking,
• the pressure leaking away before it reaches the piston (seals, rings, a cracked housing), or
• the clutch itself being worn or burnt.

That is why P0776 on these units is so often a hydraulic or mechanical problem wearing an electrical-sounding name.

Which Clutch Does Pressure Control Solenoid B Control?

Transmission	GM name for the solenoid	Clutch it controls	Gears that clutch is applied in
6L80 / 6L90	Clutch Pressure Control Solenoid 2 (OBD tables: Pressure Control Solenoid B, [C35R])	3-5-Reverse clutch	3rd, 5th and Reverse
8L90 / 8L45	Pressure Control Solenoid B (OBD tables: clutch2/CB12345R)	CB12345R clutch	As the name says: 1st through 5th and Reverse

The 8L90's clutch names are literal. GM names each friction element for the gears it is applied in, so CB12345R is a brake (the "B") applied in 1st, 2nd, 3rd, 4th, 5th and Reverse. It releases only for 6th, 7th and 8th.

That gives a quick way to read symptoms. On a 6L80, a P0776 problem shows up as trouble in 3rd, 5th and Reverse, while 1st, 2nd, 4th and 6th feel normal. On an 8L90, the affected clutch is working in almost every low gear and reverse, so a stuck-off fault can feel like slip on launch, in the lower gears and in reverse.

One more 6L80 detail from ATSG's technical guide: Clutch Pressure Control Solenoid 2 is a normally-high solenoid. With no current, it produces full pressure. That fits the 6L80's documented fail-safe: ATSG says the transmission defaults to 3rd or 5th when its electronics fail, and both of those gears use the 3-5-R clutch. A stuck-off fault is therefore rarely "the solenoid lost power." It is more often something between the solenoid and the clutch.

How Does the TCM Decide to Set P0776?

GM publishes its OBD monitor logic. The two transmissions check this clutch differently.

6L80/6L90 (GM 2011 OBD summary): the monitor is an active test.

• With the transmission in steady 3rd, it looks for 400 RPM or more of gearbox slip.
• If it finds slip, it commands 4th gear as a test. Third and 4th share the 1-2-3-4 clutch; 4th swaps the 3-5-R clutch for the 4-5-6 clutch. If 4th works but 3rd slipped, the 3-5-R clutch is the one not holding, and the module counts a failure.
• It runs the same test in steady 5th by commanding 6th, which also drops the 3-5-R clutch.
• The code sets after a set number of 3rd-gear or 5th-gear failures, on one trip.

In practice, that means the TCM may shift the truck out of 3rd or 5th on its own while it runs the test. An unexpected shift into 4th or 6th can be part of this code, not a separate problem.

8L90/8L45 (GM 2017 OBD summary for the 8-speed controller): P0776 sets when attained-gear slip is 400 RPM or more for 3 seconds or longer, repeated over three fail events, with the pressure control solenoid B clutch (clutch2/CB12345R) commanded on.

Both monitors are blocked by speed sensor codes, so a speed sensor fault has to be fixed first.

The 6L80 Bulletin That Is Not About the Solenoid

GM service bulletin 09-07-30-004J is titled "Slips in Reverse or Third, Delayed Reverse or Drive Engagement, DTC P0776, P2715, P2723, Harsh 2-3 Shifts (Inspect 1-2-3-4 / 3-5-R Housing and Pump Seal Rings)." It covers the 6L80/6L90 in:

• 2007–2008 Silverado, Sierra and Sierra Denali
• 2007–2008 Escalade, Escalade ESV and EXT, and Yukon Denali / Yukon XL Denali
• 2008 Suburban and Yukon XL
• 2006–2009 Corvette, STS-V, XLR, 2008–2009 H2 and Pontiac G8

For 2006–2008 vehicles, it lists slip or no reverse, delayed reverse, P0776, harsh 2-3 shifts, harsh 4-5 shifts or slip in 5th, and slipping on passing acceleration. The cause it gives is a cracked 1-2-3-4 / 3-5-R clutch housing. The weld cracks and the 3-5-R clutch loses its apply pressure.

The inspection is simple: soap the weld, cover the air bleed, blow shop air into the 3-5-R feed hole and look for bubbles. Bubbles mean a new housing. GM now supplies complete assembled housings for most applications. The bulletin also warns that fitting a 2008-design housing to a 2007-or-older 6L80 can cause a 2-3 flare or 3-5-R clutch distress, and that three inner seals must be installed on older units.

A second cause in the same bulletin: early one-piece pump cover seal rings could leak 1-2-3-4 and 3-5-R clutch oil and cause a harsh 2-3 shift. GM switched to a two-piece design in December 2008.

The lesson for any 6L80 with P0776: a new TEHCM will not fix a crack. On 2007–2008 trucks in particular, ask whether the 3-5-R housing has been air-checked before approving solenoid parts. Sonnax also lists 3-5-R drum weld failures as a cause of no or slipping reverse.

6L80/6L90 vs 8L90/8L45: How P0776 Differs

Item	6L80 / 6L90	8L90 / 8L45
Clutch involved	3-5-Reverse	CB12345R (clutch 2)
Where you feel it	3rd, 5th, Reverse	Launch and lower gears (1st–5th) and Reverse
TCM location	Inside the transmission, part of the TEHCM	Mounted outside the transmission; solenoids in the valve body
Solenoid replacement	Whole TEHCM; programmed to the VIN, then relearned	Valve body / solenoids; the TCM has to be updated with the new solenoid data, then Service Fast Learn
Documented non-solenoid cause	Cracked 1-2-3-4 / 3-5-R housing, pump seal rings (09-07-30-004J)	Fluid condition and converter debris are the first things to rule out; we found no P0776-specific 8L90 bulletin
Fluid	DEXRON VI	Mobil 1 Synthetic LV ATF HP on vehicles serviced under 18-NA-355

On the 8L90, programming is not optional. Gears Magazine explains that the TCM uses a part-unique number built from the valve body's solenoid serial numbers to shape each solenoid's pressure curve. Replace the valve body or solenoids without updating the TCM and the new solenoids run on the old data.

Is P0776 Electrical or Hydraulic?

Separate the two with the code list:

• Electrical codes for this solenoid are the circuit codes. On the 6L80, ATSG lists P0966 and P0967 (low / high) for Clutch Pressure Control Solenoid 2. GM's 8-speed tables list P0964 (open), P0966 (low) and P0967 (high) for Pressure Control Solenoid B.
• P0776 alone means the circuit checked out and the clutch still slipped. Look at pressure delivery and the clutch itself.

Fluid is part of the hydraulic story. Low fluid, or fluid carrying friction material, reduces the pressure that reaches the piston. GM's PI1393 for 2015 6L80/6L90 trucks warns that loose torque converter clutch material can pass through the pump and damage it, lowering line pressure and distressing clutches. Our P0741 guide covers the converter side.

Codes Commonly Seen With P0776

Code	Description	What it adds
P0776	Pressure Control Solenoid B (6L80: Clutch PCS 2, 3-5-R) Stuck Off	The fault itself
P0777	Same solenoid Stuck On	Both together suggest a sticking regulator valve or an intermittent solenoid
P0733 / P0735 / P0736 (6L80)	Incorrect 3rd / 5th / reverse ratio	The same clutch seen from the ratio side
P2715 / P2723 (6L80)	Listed with P0776 in bulletin 09-07-30-004J	Together, strongly suggests the cracked housing or seal ring problem
P0966 / P0967	Solenoid circuit low / high	Electrical. Diagnose first
P0716 / P0717 / P0722	Speed sensor faults	Block the monitor; can cause false slip readings
P0700	MIL request	The notification

Symptoms of P0776

• 6L80: slip or no drive in Reverse, delayed reverse engagement, flare or slip in 3rd or 5th, harsh 2-3 or 4-5 shifts, slipping on passing acceleration (the conditions listed in 09-07-30-004J)
• 6L80: an unexpected shift from 3rd to 4th or 5th to 6th while the TCM runs its active test
• 8L90: slip or flare on launch and in the lower gears, and weak or slipping reverse
• Check engine light on the first failure, usually with P0700
• Reduced-function or default operation
• Burnt-smelling or dark fluid if the clutch has been slipping for a while

On urgency: a slipping clutch destroys itself and contaminates the fluid, which then spreads damage through the valve body. No-reverse or slipping reverse is also a safety issue in parking lots and on ramps. Get it diagnosed promptly and do not tow.

Causes and How to Confirm Each

Cause	How to confirm it	Notes
Cracked 1-2-3-4 / 3-5-R housing (6L80)	Air-check the 3-5-R feed hole with soap on the weld, per 09-07-30-004J	Especially 2007–2008 trucks and SUVs; not a solenoid fault
Leaking pump cover seal rings (6L80)	Inspect rings; one-piece early design	Same bulletin; linked to harsh 2-3
Low or contaminated fluid	GM temperature-based level check; fluid condition	First and cheapest check
Converter or clutch debris, pump damage	Pan inspection; line pressure test	Per GM PI1393, loose converter material can lower line pressure
Sticking 3-5-R regulator valve (6L80) or clutch 2 regulator (8L90)	Valve body teardown and inspection	A common hydraulic cause; the solenoid may be fine
Solenoid not producing pressure	GM's solenoid performance test	6L80: TEHCM. 8L90: valve body/solenoid with TCM update
Worn or burnt clutch	Several ratio codes, burnt fluid, clutch material	Points to an overhaul
Wrong parts after a rebuild	2008 housing in a 2007 unit, missing inner seals, wrong valve body	09-07-30-004J warns about both housing issues

How Is P0776 Diagnosed?

1. Read all TCM codes and save the freeze frame. Note the gear and temperature when it set.
2. Identify the transmission: 6L80/6L90 or 8L90/8L45. The clutch involved is different.
3. Clear up speed sensor and circuit codes first (P0966/P0967, and P0964 on the 8-speed).
4. Check fluid level and condition with GM's procedure.
5. Check the VIN for bulletins, including 09-07-30-004J on 2006–2009 6L80 vehicles, and for software updates.
6. Road test with a scan tool: on a 6L80, check whether slip is limited to 3rd, 5th and reverse; on an 8L90, check launch and lower gears.
7. Check line pressure if slip affects more than one clutch.
8. Pan down: debris, clutch material, metal.
9. On a 6L80, air-check the 3-5-R circuit and housing. Remove the valve body to test the solenoid and inspect the regulator valve.
10. Repair what is confirmed, then program and relearn as the repair requires.

Parts and Cost

Repair	What it involves	Cost picture (estimates)
Fluid correction or service	Correct fluid and level	Lowest
Diagnosis	Scan data, line pressure, pan inspection	Moderate labor
Valve body repair	Regulator valve or bore repair	Mid-range
6L80 TEHCM	Confirmed solenoid failure; programming and relearn	Substantial
8L90 valve body / solenoids	Plus TCM update with new solenoid data	Substantial
6L80 1-2-3-4 / 3-5-R housing	Transmission out and apart; complete assembled housings available for most applications	Major repair, but it is the actual fault when the housing is cracked
Overhaul	Burnt clutches and contamination	Highest

These are general cost ranges, not quotes. Confirm by VIN and RPO.

What Other P0776 Pages Get Wrong

• Not saying which clutch. On a 6L80 it is the 3-5-Reverse clutch; on an 8L90 it is CB12345R. Symptoms and diagnosis follow from that.
• Using the 6T70 wave-plate fix. GM bulletin 09-07-30-012F (replace the 3-5 reverse wave plate) is for the front-wheel-drive 6T70/6T75 in vehicles like the Acadia, Enclave and Traverse, and PI1131 covers the 6T40/6T45. Neither applies to a Silverado or Tahoe 6L80.
• Selling a solenoid for a cracked housing. GM's 09-07-30-004J names a cracked 1-2-3-4 / 3-5-R housing as a P0776 cause.
• Treating "stuck off" as a power loss. On the 6L80 this solenoid is normally high. Loss of power applies the clutch; it does not release it.
• Skipping programming on the 8L90. New solenoids need their data loaded into the TCM.
• Ignoring the fluid. Debris and low line pressure cause clutch slip that no solenoid will fix.

A Note on Sourcing for This Code

Read directly by us: GM bulletin 09-07-30-004J (cracked housing and seal rings), GM's 2011 OBD summary tables for the 6L80/6L90 and 2017 OBD summary tables for the 8-speed controller (monitor logic and clutch names), PI1393 (converter debris), 09-07-30-012F and PI1131 (front-wheel-drive units, cited only to rule them out), 18-NA-355 (8-speed fluid), and ATSG's 6L80 technical guide for solenoid assignments and default behavior. Rebuilder sources (Sonnax, Gears Magazine, Transmission Digest) are reported and corroborated, not GM documents. Thresholds are calibration values for the model years shown. Have a dealer check your VIN for current bulletins.

Frequently Asked Questions

What does P0776 mean on a 6L80 Silverado or Tahoe?

Clutch Pressure Control Solenoid 2 Stuck Off. That solenoid controls the 3-5-Reverse clutch, so the TCM saw slip in 3rd or 5th and confirmed it by test-shifting to 4th or 6th. Expect symptoms in 3rd, 5th and Reverse.

What does P0776 mean on an 8L90?

Pressure Control Solenoid B Stuck Off, which GM's tables tie to clutch 2, the CB12345R clutch. That clutch is applied in 1st through 5th and Reverse, so slip shows up at launch, in the lower gears and in reverse.

Is P0776 just a bad solenoid?

Often not. On 2006–2009 6L80 vehicles, GM bulletin 09-07-30-004J names a cracked 1-2-3-4 / 3-5-R clutch housing and leaking pump seal rings. Sticking regulator valves, low fluid and worn clutches can also set it.

Why does my truck have no reverse with P0776?

On a 6L80, reverse uses the 3-5-R clutch. If that clutch cannot hold because of a crack, leaking seals or low pressure, reverse slips or disappears. This is the first symptom listed in GM's bulletin.

Can a fluid change fix P0776?

Only if fluid level or condition is the cause. It will not fix a cracked housing, a failed solenoid or burnt clutches. On an 8L90, use the fluid GM specifies for your vehicle; bulletin 18-NA-355 calls for Mobil 1 Synthetic LV ATF HP on converted vehicles.

Does the TCM need programming after the repair?

On a 6L80, a new TEHCM must be programmed and relearned. On an 8L90, replacing the valve body or solenoids requires a TCM update so it has the new solenoid data, followed by Service Fast Learn.

Is it safe to drive with P0776?

Briefly and gently. A slipping clutch overheats and contaminates the fluid, and slipping or missing reverse is a safety issue. Get it diagnosed promptly.

I read about a wave plate fix for P0776. Does it apply?

Not to a 6L80 or 8L90. That fix (09-07-30-012F) is for the front-wheel-drive 6T70/6T75 in crossovers like the Acadia, Enclave and Traverse.

Sources We Checked

GM documents and industry references used for this guide. Calibrations and thresholds vary by model year — confirm against current GM service information for your VIN.

• GM OBD system operation summary (transmission diagnostics)
• GM service bulletin (NHTSA copy)
• GM service bulletin (NHTSA copy)
• GM service bulletin (NHTSA copy)

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