P0796 on 2010-2017 GMC Sierra 1500: Pressure Control Solenoid 'C' Causes and Fixes

What's Unique About the 2010-2017 Gmc SIERRA 1500

This year range covers two Sierra generations and multiple transmissions. While the code can appear on the 6-speed (6L80) transmission, often due to torque converter debris, it is a particularly well-documented issue on the 8-speed (8L90) transmission introduced around 2015. General Motors has issued multiple Technical Service Bulletins (TSBs), like PIP5771B, that explicitly guide technicians to inspect the transmission pan for debris; if none is found, the recommended repair is to replace the entire valve body assembly. This indicates a known pattern of internal valve body failure on the 8-speed models, making it a more common culprit than just an individual solenoid.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: This range covers the end of the second generation (GMT900, 2010-2013) and the third generation (K2XX, 2014-2017). GMT900s primarily used the 6-speed (6L80) automatic, while K2XX models introduced the 8-speed (8L90) automatic around 2015. The 8L90 is specifically mentioned in TSBs regarding P0796 and is known for issues with its valve body and torque converter.

Symptoms You May Notice

• Harsh, jerky, or delayed gear shifts.
• Transmission slipping between gears.
• Vehicle entering 'limp mode' (stuck in a single gear).
• Check Engine Light is on.
• Vehicle stutters or bucks on acceleration or deceleration, especially at low speeds.
• Inability to go into forward or reverse gears in severe cases.
• Engine may stall when shifting or coming to a stop.

Most Likely Causes

1. Faulty Transmission Valve Body 🔴 High Probability → Shop Transmission Valve Body Specifically noted in manufacturer TSBs (#PIP5771B) for the 8-speed (8L90) transmission as the primary fix if no debris is found in the pan. The solenoids are integrated into the valve body, and internal components like accumulator pistons and shuttle valves are known to wear out, causing pressure control issues.
   How to confirm: A professional technician will use a scan tool to monitor solenoid commands and pressures. The ultimate confirmation follows the TSB diagnostic path: drop the transmission pan, and if it's clean, the presumed cause is the valve body. Vacuum testing individual circuits on the valve body can also pinpoint wear.
   Typical fix: Replacement of the transmission valve body assembly. The new valve body's PUN must be programmed to the TCM.
   Est. part cost: $500-$1300
2. Torque Converter Failure 🔴 High Probability → Shop Automatic Transmission Torque Converter Torque converter issues, including a well-known 'shudder' and internal bearing failure, are a major problem on GM trucks with both 6L80 and 8L90 transmissions. When the converter fails, it sheds metallic debris throughout the transmission, which clogs the valve body and causes solenoids to stick, leading to codes like P0796.
   How to confirm: Symptoms often include a noticeable shudder at certain speeds (like driving over a rumble strip). Finding excessive metallic debris in the transmission pan is a strong indicator of torque converter or other major internal failure.
   Typical fix: Requires transmission removal to replace the torque converter, along with a complete transmission flush or rebuild to remove all debris. The valve body is often replaced at the same time due to contamination.
   Est. part cost: $300-$800 for the torque converter
3. Contaminated or Low Transmission Fluid 🟡 Medium Probability → Shop Transmission Assembly The 8L90 transmission is sensitive to fluid type and condition. The original fluid was found to be hydroscopic (absorbs moisture), leading to shudder and accelerated wear. Debris from a failing torque converter is a primary source of contamination.
   How to confirm: Check the transmission fluid level and condition. If the fluid is dark, smells burnt, or contains metallic particles, it is contaminated. The correct fluid for the 6L80 is DEXRON VI, while the 8L90 requires a specific fluid like Mobil 1 LV ATF HP (blue label).
   Typical fix: If fluid is simply low, top it off. If contaminated, a complete fluid flush and filter change is required. If significant metal debris is found, a full transmission rebuild or replacement is likely necessary.
   Est. part cost: $75-$200 for fluid and filter
4. Failed Pressure Control Solenoid 'C' ⚪ Low Probability → Shop Transmission Clutch Pressure Control Solenoid While the code points directly to the solenoid, it's rarely the solenoid itself failing in isolation. On the 8L90, the solenoids are not typically serviced individually; they are replaced as part of the entire valve body assembly. The failure is usually due to contamination or a fault in the valve body housing.
   How to confirm: A technician can use a bi-directional scan tool to command the solenoid on and off to check its response. Resistance can also be checked with a multimeter if the solenoid is accessible.
   Typical fix: Replacement of the entire valve body assembly.
   Est. part cost: $500+ for a valve body

Rare But Worth Checking

• Damaged Wiring or Connectors: The wiring harness leading to or inside the transmission can become damaged, causing a loss of signal to the solenoid. This should be checked before replacing expensive hard parts.
• Faulty Transmission Control Module (TCM): → Shop Transmission Assembly While rare, the TCM itself can fail and stop sending the correct signal to the solenoid. TSB #PIP4831E suggests checking the TCM's date code, hinting at potential issues with certain batches.

Diagnosis Steps

1. Check the transmission fluid level and condition. Note any burnt smell, discoloration, or metallic sheen. The 8L90 requires Mobil 1 LV ATF HP fluid, not standard DEXRON VI.
2. Scan the TCM for all stored trouble codes. Note any other codes that appear with P0796, especially other solenoid or TCC codes.
3. Using a professional scan tool, monitor the commanded state vs. actual state of Pressure Control Solenoid 'C' and check live transmission data like line pressure and clutch slip speeds.
4. Perform a visual inspection of the transmission wiring harness and connectors for any visible damage, corrosion, or loose connections.
5. Following GM TSB #PIP5771B, the next step is to drop the transmission oil pan and inspect for debris.
6. If significant metallic debris or clutch material is found, a major internal failure (like the torque converter or clutch packs) is likely, requiring a transmission rebuild or replacement.
7. If the pan is clean (no significant debris), the most probable cause, especially on 8-speed models, is a faulty valve body, which should be replaced.
8. After repairs, the new valve body's PUN must be programmed to the TCM, all codes must be cleared, and a transmission adaptive pressure relearn procedure must be performed during a road test.

Parts You'll Likely Need

• Transmission Valve Body (OEM #24297899 (supercedes older numbers like 24272846, 24274844, 24273239)) — This is the most common fix recommended by GM's own Technical Service Bulletins for the 8-speed transmission when no debris is found in the pan.
  Trusted brands: ACDelco (OEM), Sonnax (Aftermarket upgrade kits), Street Smart Transmission (Remanufactured)
  OEM price range: $700-$1300
  Aftermarket price range: $500-$900
• Transmission Filter and Gasket Kit — This is required whenever the transmission pan is removed for inspection or service.
  Trusted brands: ACDelco, Wix, ATP
  OEM price range: $60-$100
  Aftermarket price range: $30-$60
• Torque Converter — If significant metallic debris is found in the pan, the torque converter is the likely source of failure and must be replaced.
  Trusted brands: ACDelco (OEM), Transtar, Whatever It Takes (W.I.T.)
  OEM price range: $400-$800
  Aftermarket price range: $300-$600

Related Codes That Often Appear With This One

• P2714 — This code is for 'Pressure Control Solenoid 'D' Performance/Stuck Off'. TSBs #PIE0645 and #PIP4831E list it alongside P0796, indicating a common failure pattern within the valve body affecting multiple solenoids.
• P0741 — This code relates to Torque Converter Clutch (TCC) Circuit Performance. A failing torque converter can cause both codes by sending debris into the valve body or by causing pressure fluctuations.

Technical Service Bulletins (TSBs) & Recalls

• PIP5771B
• PIP5771
• PIP5425A
• PIP4831E
• PIE0645

Platform-Specific Known Issues

• 8L90 Transmission Shudder and Class Action Lawsuit: → Shop Transmission Assembly The 8-speed 8L90 transmission is the subject of a class-action lawsuit for a 'shudder' or 'vibration' issue, often linked to the torque converter and contaminated transmission fluid. This underlying issue is a major contributor to debris in the system, which can directly cause the P0796 code by clogging the valve body.
• Valve Body Wear Points: → Shop Transmission Valve Body Beyond just solenoids, the 8L90 valve body has known wear points in its hydraulic circuits, including the pressure regulator valve and accumulator piston bores (VFS dampeners). Wear in these areas leads to pressure loss and erratic solenoid performance, setting codes like P0796 even if the solenoid itself is electrically fine.

Mechanic-Grade Diagnostic Values

• Pressure Control Solenoid Resistance (8L90 Transmission) — expected: 4.5 - 5.5 Ohms. Failure: Readings outside this range indicate a faulty solenoid.
• Pressure Control Solenoid Resistance (6L80 Transmission, PWM Type) — expected: 3 - 8 Ohms. Failure: Readings outside this range suggest a failed solenoid.
• Shift Solenoid Resistance (6L80 Transmission, On/Off Type) — expected: 20 - 40 Ohms. Failure: Readings outside this range indicate a faulty solenoid.
• Transmission Line Pressure at Idle (6L80/8L90) — expected: 55-80 psi. Failure: Pressure below this range at idle can indicate a weak pump, internal leaks, or a stuck pressure regulator valve.

Scan Tool Commands That Help

• GDS2 (GM Dealer Software): Transmission Service Fast Learn — Required after replacing the valve body, transmission, or performing major repairs. It's a stationary procedure that allows the TCM to learn the hydraulic characteristics of the new components before driving.
• GDS2 (GM Dealer Software): Transmission Adaptive Values Learn — Used to reset and relearn clutch apply pressures to correct shift quality issues. This can be done as a stationary procedure or through a specific driving cycle.
• GDS2 (GM Dealer Software): Solenoid Valve Characterization Reprogramming — This is critical when replacing the valve body or an individual solenoid on an 8L90. The new component's Part Unique Number (PUN) must be programmed into the TCM to ensure the correct solenoid flow rate data is used.
• Professional Scan Tool: Command Solenoid 'C' ON/OFF — Used during diagnosis to check if the solenoid responds to commands from the TCM. A technician can monitor line pressure with a gauge while commanding the solenoid to see if the pressure changes as expected. A lack of response indicates a failed solenoid or circuit.

Wiring & Ground Locations

• Main Transmission Connector (8L90) — A 20-way (or 36-way on some variants) electrical connector on the passenger side of the transmission case.. This is the primary connection point between the external vehicle harness and the internal transmission harness (which includes the solenoids). Checking for corrosion, pin damage, or a loose connection here is a crucial first step in diagnosing an electrical fault for P0796.
• Internal Transmission Harness (8L90) — Located inside the transmission, connected to the valve body and solenoids. It must be removed before the valve body can be taken out.. This harness can fail, causing codes like P0711 (Temp Sensor) or solenoid codes. GM has issued bulletins (e.g., PIP5700A) with updated part numbers for a two-piece replacement harness, as the original one-piece design is no longer available.
• TCM Ground — The TCM for the 8L90 is an external module, not inside the transmission like the 6L80. Its ground points are typically located on the chassis or engine block near its mounting location. A bad ground can cause erratic behavior and false codes.. A poor ground connection to the TCM can cause incorrect readings and faulty solenoid commands, potentially triggering a P0796 code even if the transmission itself is healthy.

Real Owner Repair Stories

• YouTube channel 'Service Information' (2016 GMC Sierra, 5.3L V8, 6L80 transmission, 110,000 miles) — Check Engine Light on, slipping, stuttering, then no forward or reverse gear engagement. P0796 code stored.
  ❌ Tried (didn't work) Initial diagnosis pointed to the pressure control solenoid based on the code.
  ✅ What actually fixed it Upon dropping the transmission pan, excessive metallic debris was found. The root cause was a failed torque converter that came apart, sending debris through the transmission pump. This damaged the pump, causing a loss of line pressure which burned out the forward clutches. The final fix was a complete transmission replacement/rebuild including a new torque converter.

OEM Part Supersession History

• Various one-piece internal wiring harnesses → Two-piece harnesses (e.g., Pass-Thru Harness 24297371 and Valve Body Harness 24298757/24298758) — Serviceability and parts availability. The one-piece harnesses are no longer available for the 8L90 transmission.
  Heads up: Technicians must identify the internal mode switch (10-pin vs 4-pin) and whether the vehicle has start-stop (ESS) to order the correct combination of the two new harnesses, as detailed in GM bulletin PIP5700A.

Model Year Variations Within This Range

• 2015-2017: The 8-speed 8L90 (RPO code M5U) was introduced as an option around 2015, primarily on trucks with the 6.2L L86 engine, while the 6-speed 6L80 remained standard on 5.3L models. The causes for P0796 differ significantly, with the 8L90 being prone to valve body failure and the 6L80 more often suffering from torque converter debris.
• 2019+ (Post-range but relevant context): For the 2019 model year, GM trucks with the 8L90 switched from Active Fuel Management (AFM) to Dynamic Fuel Management (DFM). This change in engine control strategy also led to changes in the valve body casting and a specific control valve (S4/23468), making later valve bodies incompatible with earlier models.