P0776 on 2010-2017 Chevrolet Equinox: Pressure Control Solenoid 'B' Causes and Fixes

What's Unique About the 2010-2017 Chevrolet Equinox

For the 2010-2017 Equinox, particularly earlier models (2010-2012), P0776 is very frequently a symptom of a larger mechanical failure inside the 6T40/6T45 transmission. A specific part called the '3-5-R wave plate' is known to break. When it fails, metal debris contaminates the entire transmission, clogging the valve body and solenoids, and causing the loss of 3rd, 5th, and Reverse gears. Simply replacing the solenoid without addressing this underlying mechanical failure will not fix the problem. GM acknowledged this widespread issue by issuing Special Coverage Adjustment #14404 for some affected vehicles, extending the warranty for this specific failure.

Symptoms You May Notice

• Inability to engage Reverse, 3rd, or 5th gears
• Harsh, delayed, or slipping shifts
• Check Engine Light or Transmission Warning Light is on
• Transmission enters 'limp mode,' often stuck in a single gear (typically 2nd gear)
• Vehicle may not move at all
• Flashing gear selector indicator
• Engine RPMs may spike excessively high while in Park, as noted in NHTSA ODI #10979593

Most Likely Causes

1. Broken 3-5-R Wave Plate 🔴 High Probability This is a well-documented design flaw in the Gen 1 GM 6T40/6T45 transmission used in these vehicles. GM issued Technical Service Bulletin PI0780A and Special Coverage #14404 about this exact issue. The original wave plate was prone to fracturing due to fatigue. Manufacturer Bulletin #PI0780A specifically provides repair information for cases involving a slip, no reverse, or no forward condition when DTC P0776 is set.
   How to confirm: A technician will check the transmission fluid for excessive metallic debris. The ultimate confirmation requires transmission disassembly and visual inspection of the clutch pack components, as air checks are considered unreliable per TSB PI0670A.
   Typical fix: This requires a partial or full transmission rebuild. The broken wave plate must be replaced with the updated part (GM P/N 24254103 mentioned in TSB 09-07-30-012F), along with the 3-5-R piston. The entire transmission must be disassembled and cleaned of all metal debris. The valve body, solenoids, and filters must be thoroughly cleaned or replaced.
   Est. part cost: $200-$500 for rebuild kits and plates
2. Failed TEHCM (Transmission Electro-Hydraulic Control Module) 🟡 Medium Probability The TEHCM, which houses all the solenoids, is located inside the transmission where it is subjected to heat and contaminated fluid. Debris from a failing wave plate can clog and damage the solenoids and pressure switches within the TEHCM. Sometimes the laminate discs on the internal pressure switches fail on their own on Gen 1 models.
   How to confirm: After confirming the 3-5-R wave plate is intact, a technician can run diagnostic tests on the solenoid circuits using a GM-specific scan tool. TSB PI0670A advises this as a potential cause if mechanical inspection reveals no damage.
   Typical fix: Replacement of the TEHCM. This part is inside the transmission and requires removing the side cover of the transmission case. The new module must be programmed to the vehicle. In some cases, the pressure switch laminate discs on Gen 1 TEHCMs can be rebuilt using a kit like the Sonnax 124740-30K to salvage an otherwise functional TEHCM.
   Est. part cost: $300-$600
3. Low or Contaminated Transmission Fluid ⚪ Low Probability While possible, this is more often a symptom of the broken wave plate than the root cause. GM TSB 16-NA-092 notes that fluid may appear dark from the factory and should not be immediately condemned without further diagnosis.
   How to confirm: Check the transmission fluid level and condition. Note that many of these vehicles do not have a traditional dipstick, requiring a specific procedure to check the fluid level.
   Typical fix: Perform a transmission fluid and filter change. However, if the code is caused by a mechanical failure, this will not solve the problem and is a waste of money.
   Est. part cost: $100-$200 for fluid and filter

Diagnosis Steps

1. Scan the TCM for all stored codes and review freeze-frame data.
2. Check the transmission fluid level and condition. Look for a dark, metallic appearance, which indicates severe internal wear (but be aware of TSB 16-NA-092).
3. If heavy debris is found, suspect a broken 3-5-R wave plate. The transmission will likely need to be removed and disassembled for inspection and repair.
4. If the fluid is clean, a technician may perform a 'Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test' using a high-level scan tool to check the TEHCM's function.
5. Inspect the wiring harness and connectors to the transmission for any damage or corrosion.
6. Based on GM TSBs, the most reliable diagnosis for a suspected wave plate failure is visual inspection, which requires significant disassembly. Air checks are explicitly noted as being unreliable.

Parts You'll Likely Need

• 3-5-Reverse Clutch Plate Kit (including updated wave plate) (OEM #24254103) — This is the most common mechanical failure point that triggers code P0776 on this platform, as documented in GM TSB PI0780A and TSB 09-07-30-012F.
  Trusted brands: ACDelco, Sonnax
  OEM price range: $50-$100
  Aftermarket price range: $30-$70
• Transmission Control Module (TEHCM) (OEM #24258562) — If mechanical parts are intact, the integrated solenoid pack within the TEHCM is the next likely cause. It can also be damaged by debris from a mechanical failure. This part number is for Gen 1 6T40/6T45 transmissions.
  Trusted brands: ACDelco
  OEM price range: $400-$600
  Aftermarket price range: $250-$450
• Transmission Filter and Gasket Kit — This must be replaced during any internal transmission repair, especially after a wave plate failure, to remove contaminants. TSBs explicitly state the control solenoid filter plate and pump fluid filter must be replaced.
  Trusted brands: ACDelco
  OEM price range: $40-$70
  Aftermarket price range: $20-$50

Related Codes That Often Appear With This One

• P0700 — This is a general transmission fault code that requests the Check Engine Light to be turned on. It will almost always be present with any specific transmission DTC like P0776.
• P0796 — This code relates to the Pressure Control Solenoid 'C' and can be set along with P0776 if the internal damage or debris is affecting multiple hydraulic circuits.
• P0777 — This code is for 'Pressure Control Solenoid 'B' Stuck On', the opposite of P0776. It can be set as a consequence of the same wave plate failure.
• P2714 — This code is for 'Pressure Control Solenoid 'D' Performance/Stuck Off' and can also be triggered by debris from the wave plate failure affecting other solenoids.

Technical Service Bulletins (TSBs) & Recalls

• PI0780A: Addresses slips or no Reverse/3rd/5th gear and DTC P0776, pointing to a broken 3-5-R apply (waved) plate.
• PI0670A: Provides diagnostic tips for P0776, emphasizing visual inspection of the 3-5-R clutch piston over unreliable air checks.
• 16-NA-092: Notes that dark transmission fluid is not necessarily a sign of failure on these transmissions and to proceed with diagnostics.
• 09-07-30-012F: An earlier TSB also detailing the P0776 code, loss of gears, and the fix being the replacement of the 3-5-R wave plate. It lists the updated wave plate part number as 24254103.
• 14404: Special Coverage Adjustment for the fractured 3-5-R wave plate, extending warranty coverage to 10 years/120,000 miles for affected vehicles.
• Bulletin #PI0780A: Provides repair information to correct customer concerns of slip, no reverse, no forward, or MIL illumination with DTC P0776.

Platform-Specific Known Issues

• A high failure rate of the 3-5-R wave plate in the 6T40/6T45 transmission is the most significant issue related to this code. The original part was prone to breaking, and updated designs are available.
• GM issued a Special Coverage Adjustment (#14404) extending the warranty to 10 years or 120,000 miles for this specific failure on some model years, indicating the widespread nature of the problem.

Mechanic-Grade Diagnostic Values

• Pressure Control Solenoid (PCS) Resistance — expected: 3 to 5 Ohms. Failure: A reading outside this range, or an open/short circuit, indicates a failed solenoid.
• On/Off Shift Solenoid Resistance — expected: 16 to 20 Ohms. Failure: A reading outside this range indicates a failed solenoid.
• Pressure Switch Resistance (Gen 1 TEHCM only) — expected: 0.5 to 10 Ohms (normally closed). Failure: An Open Loop (O.L.) reading in the resting state or failure to go to O.L. when the switch is manually pressed indicates a faulty switch.
• P0776 Set Condition (Live Data) — expected: Transmission input shaft speed should closely match the commanded (anticipated) speed for the gear.. Failure: The code sets when the input shaft speed is >= 200 RPM away from the anticipated speed for 3 seconds while the 3-5-R clutch is commanded ON.

Hidden / Shadow Codes Worth Checking

• Check for P0842 (and other pressure switch codes): This is not a hidden code itself, but its status in the scan tool reveals critical information. If pressure switch DTCs are listed as 'valid' codes for the vehicle, it has a Gen 1 transmission. If they are listed as 'invalid', it is a Gen 2 or later transmission. (see via A professional scan tool (like GM GDS2) that can show the list of all possible valid and invalid DTCs for a given module.)

Scan Tool Commands That Help

• GM GDS2 or equivalent professional scan tool: Solenoid Cleaning Procedure — This automated process should be performed before deeper diagnosis if debris is suspected but a full teardown is not yet justified. It cycles the solenoids under pressure to dislodge contaminants.
• GM GDS2 or equivalent professional scan tool: Solenoid Performance Test — Used with a Kent Moore DT-47825 tool kit to functionally test a solenoid. The scan tool commands the solenoid on and off while a technician observes an air pressure gauge to confirm mechanical operation.
• GM GDS2 or equivalent professional scan tool: Fast Learn Procedure — This is required after replacing the TEHCM or servicing the valve body to reset and relearn transmission adaptive values for proper shifting.

Wiring & Ground Locations

• Transmission Case Connector (14-pin) — The main external electrical connector on the transmission case.. Provides all power, ground, and communication between the vehicle and the internal TEHCM. Corrosion or damage to Pin 12 (Ignition Voltage), Pin 2 (Ground), or Pins 6 & 14 (GMLAN) can cause various transmission codes, including P0776.
• G110 — On the right rear of the engine, often mounted to the back of the cylinder head.. This is a primary engine and transmission component ground. A loose or corroded connection at G110 can cause erratic behavior from the TEHCM and other modules, potentially triggering false solenoid codes.

OEM Part Supersession History

• Various (e.g., 24252423, 24256523) → 24258562 (for PRE-2010 Gen 1 models) — Internal revisions and updates by the manufacturer.
  Heads up: There is a hard split between pre-2010 and post-2010 Gen 1 TEHCMs. Part number 24258562 is for pre-2010 models. Post-2010 Gen 1 models use a different set of part numbers (e.g., 24256524). They are not interchangeable.

Model Year Variations Within This Range

• 2010-2012 (approx.): These models use the 'Gen 1' 6T40/45 transmission. The TEHCM is identified by a number in the 8th digit of its barcode, and it contains five internal pressure switches that are a known failure point. This generation is susceptible to the 3-5-R wave plate failure.
• 2013-2017 (approx.): These models use the 'Gen 2' 6T40/45 transmission. The TEHCM is identified by a letter (B, C, or D) in the 8th digit of its barcode and does NOT have internal pressure switches. The valve body and some solenoid functions/locations are different from Gen 1. While more reliable, they can still suffer from TEHCM failure.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Excessive Oil Consumption (2.4L Ecotec) 🔴 High — Very common, especially in 2010-2013 models. Caused by prematurely worn piston rings. Can lead to engine damage if not monitored closely. (Ref: Special Coverage Adjustment #14159; Subject of multiple class-action lawsuits.)
• Stretched Timing Chain (2.4L Ecotec) 🔴 High — Common, often exacerbated by the excessive oil consumption issue leading to low oil levels. Symptoms include a rattling noise on startup. Failure can cause catastrophic engine damage. (Ref: Special Coverage Adjustment #12313C for the balance chain.)
• Clogged/Frozen PCV Orifice (2.4L Ecotec) 🟠 Medium — Occurs in cold weather, especially on engines with high oil consumption. Can cause high crankcase pressure, leading to blown seals (e.g., rear main seal). (Ref: TSB #14882)
• Failed VVT Solenoids 🟡 Low — Relatively common but an easy and inexpensive fix. Causes rough idle, stalling, and sets codes like P0010 or P0011.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used TEHCM can be a cost-effective option IF it is confirmed to be the correct generation (Gen 1 vs. Gen 2) and part number series for the vehicle. However, it carries the risk of having the same internal flaws as the original part.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Verify the 8th digit of the barcode on the TEHCM: a number for Gen 1, a letter for Gen 2. It MUST match your original.
• Ask for the donor vehicle's VIN to check for a history of transmission problems.
• If buying a complete used transmission, assume the 3-5-R wave plate (on Gen 1) is a potential failure point and factor in the cost of replacing it proactively.

OEM-only on this vehicle (don't cheap out):

• TEHCM (ACDelco brand is OEM). While aftermarket options exist, OEM is the most reliable choice. A remanufactured OEM unit is also a good option.
• 3-5-R Wave Plate. Always use the updated design part from a reputable source like ACDelco or Sonnax.

Aftermarket brands forum-validated for this vehicle:

• Sonnax: Widely respected for transmission rebuild components, including valve body zip kits, pressure switch repair kits (for Gen 1), and updated mechanical parts.

Brands owners have reported issues with on this vehicle:

• Unbranded, no-name TEHCMs or solenoids from online marketplaces. These often have high failure rates and may not be programmed correctly.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Documented NHTSA Reports

Related OBD-II Codes

• P0700 — Transmission Control System (MIL Request). This is a generic code that is almost always stored alongside P0776. It indicates that the TEHCM has detected a fault and has requested the main engine computer to turn on the Check Engine Light.
• P0777 — Pressure Control Solenoid 'B' Stuck On. This is the companion code to P0776. Both codes point to a malfunction in the same solenoid circuit within the TEHCM. A failing solenoid or TEHCM could potentially set either code depending on the failure mode.
• P0741 — Torque Converter Clutch Circuit Performance or Stuck Off. The most common cause of P0776 is a broken wave plate, which sends metallic debris throughout the transmission. This debris can clog and damage other solenoids, such as the TCC solenoid, causing P0741 to appear alongside P0776.
• P0796 — Pressure Control Solenoid 'C' Performance or Stuck Off. Similar to P0741, this code can be triggered by the same root causes as P0776: either widespread contamination from a mechanical failure (wave plate) affecting multiple solenoids, or an electronic failure within the TEHCM that houses all the solenoids.
• U0101 — Lost Communication With TCM. Since the TEHCM acts as the Transmission Control Module (TCM) and is located inside the transmission, an internal electronic failure of the module can cause it to stop communicating with other modules on the vehicle's network, triggering this code.

Frequently Asked Questions