P0877 on 2009-2010 GMC Sierra 2500: Transmission Pressure Switch 'D' Circuit Low Fixes

What's Unique About the 2009-2010 Gmc SIERRA 2500

The 2009-2010 Sierra 2500 uses a 6L90 transmission where the pressure switches, solenoids, and the Transmission Control Module (TCM) are all integrated into one unit inside the oil pan, called the TEHCM (Transmission Electro-Hydraulic Control Module). This design means that a failure of a single, small pressure switch often requires the replacement and reprogramming of the entire expensive module. A very common failure is the tearing of the small, orange, rubber-like laminate diaphragms over the pressure switches, which are not serviced separately from the TEHCM by GM. GM has issued multiple Technical Service Bulletins (TSBs) 🎬 Watch: How to fix fault codes P0877 and P0989 related to pressure switch codes on this platform, indicating it's a well-documented issue.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light is on
• Transmission stuck in one gear (limp mode)
• Harsh or delayed shifting
• Vehicle may not move when put into gear
• Erratic shifting patterns
• Smell of overheated or burnt transmission fluid

Most Likely Causes

1. Failed Transmission Fluid Pressure (TFP) Switch / TEHCM 🔴 High Probability → Shop Transmission Assembly The pressure switches are integrated into the TEHCM. A widely recognized failure point is the tearing or dislodging of the small laminate diaphragms (often orange-colored) over the pressure switches, which are not serviced separately from the entire module by the manufacturer.
   How to confirm: After confirming external wiring is intact, a technician will drop the transmission pan and inspect the TEHCM. A scan tool can monitor the TFP Switch 4 status in real-time; it should read 'HIGH' in 5th and 6th gear and 'LOW' otherwise. If it's stuck 'LOW', the switch is bad. Visual inspection often reveals the damaged diaphragm.
   Typical fix: Replace the entire TEHCM assembly inside the transmission pan. The new module must be programmed to the vehicle's VIN. Some specialist shops offer a repair service for the diaphragms without replacing the whole unit. 🎬 See how to reseal the pressure switches yourself
   Est. part cost: $450-$700
2. Low or Contaminated Transmission Fluid 🟡 Medium Probability → Shop Transmission Assembly
   How to confirm: Check the transmission fluid level and condition using the dipstick per the owner's manual 'hot check' procedure. The fluid should be at the correct level, bright red, and not smell burnt.
   Typical fix: Top off the fluid if low and repair any leaks. If the fluid is dirty or burnt, a complete fluid and filter change is necessary. Use only DEXRON-VI specification fluid. Note: This will not fix a faulty switch, but it is a critical first step and can sometimes resolve pressure-related issues if the level was critically low.
   Est. part cost: $60-$150
3. Damaged Internal or External Wiring ⚪ Low Probability
   How to confirm: Inspect the main 16-pin electrical connector on the outside of the transmission for corrosion, moisture, or bent pins. If that is clean, the internal harness connecting to the TEHCM must be inspected after dropping the pan. A forum member on DuramaxDiesels.com reported fixing a P0877 by tightening the female pin connectors inside the pan and at the main plug.
   Typical fix: Clean and repair the external connector with dielectric grease. If the internal harness is damaged, it must be replaced. In some cases, simply improving the pin fitment at the connectors can resolve the 'circuit low' fault.
   Est. part cost: $5-$200

Rare But Worth Checking

• Debris in Valve Body Separator Plate: → Shop Transmission Valve Body GM TSB #PIP4972C and the related #PIP5100A mention that debris, sometimes from aftermarket filter packaging like shrink-wrap, can block small orifices in the valve body, leading to pressure codes like P0877 and a no-move condition.
• Faulty Powertrain Control Module (PCM) or TCM: This is very rare. The TCM is part of the TEHCM, so it gets replaced with that unit. A separate PCM failure would typically set multiple other communication or performance codes, not just P0877 in isolation.

Diagnosis Steps

1. Check the transmission fluid level and condition. Ensure it is full and the fluid is clean and red, using the proper hot check procedure.
2. Use an OBD-II scanner to check for any other transmission-related codes. Diagnose codes listed in the TSB (like P0701) first if present.
3. Thoroughly inspect the main external transmission electrical connector (16-pin) for corrosion, moisture, or backed-out pins. Clean and secure it as needed.
4. If external checks are good, the problem is internal. Safely raise the vehicle, drain the transmission fluid, and remove the oil pan.
5. Visually inspect the internal wiring harness for any signs of damage.
6. Using a scan tool, monitor the state of TFP Switch 4. Command gears 5 and 6; the switch state should change from 'Low' to 'High'. If it remains 'Low', the switch has failed.
7. If the switch fails the test, remove the valve body and TEHCM assembly. Visually inspect the pressure switch diaphragms for tears or distortion.
8. If the TEHCM is confirmed faulty, replace the entire assembly.
9. Install the new TEHCM, a new transmission filter, and a new pan gasket. Refill with DEXRON-VI fluid to the correct level.
10. Program the new TEHCM to the vehicle using a compatible J2534 programming tool.

Parts You'll Likely Need

• Transmission Electro-Hydraulic Control Module (TEHCM) (OEM #24256861 (Verify by VIN, as multiple part numbers exist, e.g., 24256657)) — This is the most common cause of P0877. It contains the fluid pressure switches, solenoids, and the TCM in one assembly. The 'D' switch fails internally within this module.
  Trusted brands: ACDelco GM Genuine Parts, Sonnax (Remanufactured), Dorman (Remanufactured)
  OEM price range: $450-$700
  Aftermarket price range: $350-$600
• Automatic Transmission Fluid (DEXRON-VI) — Required for refilling the transmission after dropping the pan to replace the TEHCM. A typical pan drop requires 6-9 quarts.
  Trusted brands: ACDelco, Valvoline, Castrol
  OEM price range: $8-$12 per quart
  Aftermarket price range: $7-$10 per quart
• Transmission Filter and Pan Gasket Kit — The filter and gasket should always be replaced whenever the transmission pan is removed.
  Trusted brands: ACDelco, ATP, Wix
  OEM price range: $40-$70
  Aftermarket price range: $25-$50

Related Codes That Often Appear With This One

• P0700 — This is a generic code indicating the Transmission Control Module (TCM) has requested the check engine light. It will almost always appear alongside a specific transmission code like P0877.
• P0751, P0756, P0761, P0776 — These are shift solenoid performance codes. TSB #PIP4379N lists them with P0877, suggesting a common internal hydraulic or electrical issue within the TEHCM.
• P0872, P0989 — These codes are for the 'C' and 'E' pressure switch circuits. If multiple pressure switch codes appear together (e.g., P0872, P0877, P0989), it strongly points to a failing TEHCM or a widespread electrical issue within the module, often due to multiple torn diaphragms.
• P2723 — This is a pressure control solenoid performance code. It is mentioned in TSBs as a possible related code when debris blocks valve body orifices.

Technical Service Bulletins (TSBs) & Recalls

• PIP4379N: Mentions P0877 as part of a large group of DTCs that can be set due to a loss of transmission pump prime or range inhibit. It advises following diagnostics for P0701 first.
• PIP4972C: Notes that P0877 and a no-move condition can be caused by debris from aftermarket filter packaging blocking orifices in the valve body separator plate.

Platform-Specific Known Issues

• Per TSB #PIP4379N, this code is often found with a wide range of other transmission codes, pointing to a potential loss of transmission pump prime or an internal hydraulic/electrical fault. The bulletin advises diagnosing P0701 first if it is present.
• Per TSB #PIP4972C and #PIP5100A, debris from aftermarket parts (specifically shrink-wrap from spin-on filters) can clog the valve body separator plate, causing this code and a potential no-move condition.

Mechanic-Grade Diagnostic Values

• Transmission Fluid Pressure (TFP) Sensor/Switch 'D' Circuit Voltage — expected: Switches between HIGH (>4.5V) and LOW (<0.5V) depending on commanded gear.. Failure: A sustained reading below 0.5V when the switch should be HIGH will trigger code P0877.
• TFP Switch Scan Tool Data State — expected: The scan tool parameter for TFP Switch 4 should display 'LOW' or 'HI' (or Open/Closed). For a 6L90, Switch 4 should be 'HI' in 5th and 6th gears.. Failure: If the scan tool data is stuck on 'LOW' even when commanding 5th or 6th gear, the switch or its circuit has failed.

Scan Tool Commands That Help

• GDS2 / Tech2: Transmission Adaptive Values Learn / Fast Learn — This procedure is mandatory after replacing the TEHCM or performing major transmission service. It allows the TCM to relearn clutch apply pressures and shift timing for smooth operation.
• J2534 Pass-Thru Device with GM SPS2/Techline Connect: Module Reprogramming — This is required to program a new TEHCM with the vehicle's specific VIN and software calibration. The vehicle will not operate correctly (or at all) until this is done.
• GDS2 / High-End Scan Tool: Solenoid Output Overrides — Allows a technician to command individual solenoids on and off to verify their mechanical and electrical function, helping to isolate a faulty solenoid from a pressure switch or wiring issue.

Wiring & Ground Locations

• Main Transmission Connector (16-pin) — On the passenger side of the 6L90 transmission case.. This is the main interface between the vehicle's wiring harness and the internal TEHCM. Corrosion, moisture, or loose pins in this connector can directly cause a 'Circuit Low' fault like P0877.
• G103 — On the passenger side cylinder head.. A faulty ground at this location has been documented to cause multiple, erratic transmission codes that can mimic a complete TEHCM failure. Cleaning this ground point can resolve complex electrical issues.

Real Owner Repair Stories

• DuramaxDiesels.com forum user (2006 Chevrolet Silverado (similar 6L transmission design)) — P0877 code present.
  ❌ Tried (didn't work) Replacing the Pressure Switch Manifold (PSM), which is the equivalent of the TEHCM's switch portion in some transmissions.
  ✅ What actually fixed it The actual cause was a poor mechanical connection. The female pins inside the PSM connector and the main transmission plug were loose. Tightening the pins with a pick tool and applying dielectric grease resolved the code permanently.
• Premier Automotive Diagnostics / Reddit (GM Vehicle with 6T70/6T75 (similar TEHCM design)) — Codes P0877 and P0989 stored, intermittent shutter during shifts.
  ❌ Tried (didn't work) Initial diagnosis suggested TEHCM replacement.
  ✅ What actually fixed it Upon inspection, the orange, laminated pressure switch diaphragms inside the TEHCM had ruptured and were pushed out of their bores. The fix was to install a pressure switch rebuild kit (new diaphragms and seals from a brand like Sonnax or TransGo), which is significantly cheaper than replacing the entire TEHCM.
• Tahoe Yukon Forum user (2007 Yukon Denali (6L80 transmission)) — Multiple transmission codes including P0842, P0872, and P0877; erratic shifting.
  ❌ Tried (didn't work) Replacing the entire TEHCM assembly.
  ✅ What actually fixed it The problem was traced to a faulty ground connection at G103, located on the passenger side cylinder head. Cleaning the ground stud and terminals resolved all the electrical faults that the new TEHCM did not fix.

When the Usual Fixes Don't Work

• While the vast majority of P0877 codes are fixed by replacing the TEHCM, there are documented cases where this expensive repair fails to solve the problem. In one instance involving a similar GM truck, a new TEHCM did not clear the code; the ultimate fix was tightening loose female pins in the transmission's electrical connectors, which cost nothing in parts. In another case with multiple pressure switch codes, a TEHCM replacement was also ineffective, and the root cause was discovered to be a corroded ground strap (G103) on the engine block, which, once cleaned, resolved all transmission faults. These instances highlight the importance of verifying all electrical connections and grounds before condemning the TEHCM.

OEM Part Supersession History

• 24256670 → 24256861, 19431596 — Hardware and software revisions to improve solenoid performance and pressure switch durability.
  Heads up: TEHCMs are not backward or forward compatible. The module must match the vehicle's specific year and calibration. Installing the wrong part number can result in a no-start condition, immediate limp mode, or programming failure.