P0873 on 2006-2010 GMC Sierra: Transmission Pressure Switch 'D' Circuit High Causes and Fixes

What's Unique About the 2006-2010 Gmc SIERRA

The 2006-2010 GMC Sierra spans two generations and two common automatic transmissions: the 4-speed 4L60-E/4L65-E (common through 2008) and the 6-speed 6L80 (common 2009+). For both transmissions, the internal transmission fluid pressure (TFP) manifold switch is a well-documented weak point. On the 4L60-E, it's a standalone plastic manifold. On 6L80 models, these switches are integrated into the Transmission Electro-Hydraulic Control Module (TEHCM). The plastic and rubber components of these switches, particularly the laminated discs on the 6L80 TEHCM, are known to degrade, tear, and delaminate from heat and chemical exposure, leading to electrical faults like P0873.

Diagnostic Flowchart

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

Generation note: The 2006 model year is part of the first generation (GMT800), while 2007-2010 models are the second generation (GMT900). GMT800 trucks typically have the 4L60-E/4L65-E 4-speed transmission. GMT900 trucks may have the 4-speed, but many 2009 and 2010 models are equipped with the 6L80 6-speed. The root cause (failed pressure switch) is common to both, but the specific part, location, and repair complexity differ significantly between the 4-speed and 6-speed.

Symptoms You May Notice

• Check Engine Light is on
• Transmission stuck in one gear (limp mode, usually 2nd or 3rd)
• Harsh or erratic shifting
• Inability to shift gears
• Loss of reverse gear
• Poor acceleration
• Flashing PRNDL (gear indicator) display

Most Likely Causes

1. Failed Transmission Fluid Pressure (TFP) Manifold Switch 🔴 High Probability → Shop Transmission Assembly This is a widely documented failure point on both the 4L60-E and 6L80 transmissions. On the 4L60-E, the entire manifold fails. 🎬 Watch: 4L60E manifold pressure switch common issues and service guide. On the 6L80, the pressure switch diaphragms, which are part of the TEHCM, are known to tear or delaminate.
   How to confirm: A professional scan tool can monitor the state of each pressure switch. The switch for circuit 'D' will show an incorrect state (e.g., 'OFF' or high voltage when it should be 'ON' or low voltage). The definitive test is to drop the transmission pan and visually inspect the switch assembly. On a 6L80 TEHCM, look for torn or dislodged orange laminate discs.
   Typical fix: For 4L60-E: Drop the transmission pan, unbolt the old TFP manifold switch from the valve body, and install the new one. For 6L80: Drop the pan, remove the valve body, and either replace the entire TEHCM (requires programming) or replace just the pressure switch plate/membrane on the TEHCM. A new transmission filter and fluid should be installed at the same time.
   Est. part cost: $50-$150 (4L60-E switch), $150-$500 (6L80 TEHCM/repair kit)
2. Damaged Wiring or Connectors ⚪ Low Probability The internal wiring harness is constantly submerged in hot transmission fluid, which can make the connectors and wiring brittle over time, leading to cracks and poor connections.
   How to confirm: Visually inspect the external transmission wiring harness for any signs of damage, corrosion, or loose connections. If external wiring is good, inspect the internal harness after dropping the pan. Test for continuity and shorts using a multimeter on the specific wire for the 'D' switch.
   Typical fix: Repair or replace the damaged section of the wiring harness. If the internal harness is brittle, it should be replaced.
   Est. part cost: $10-$150
3. Contaminated or Low Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly
   How to confirm: Check the transmission fluid level and condition. If the fluid is very dark, burnt-smelling, or contains metal particles, it indicates a more severe internal problem. While this can contribute to issues, it's less likely to be the direct cause of a 'Circuit High' code than a failed switch. TSB PIP4379K notes that low fluid can cause a loss of pump prime and set various codes, including P0873.
   Typical fix: Perform a transmission fluid and filter change. If the fluid is heavily contaminated, a transmission flush or rebuild may be necessary.
   Est. part cost: $75-$200 for fluid and filter

Rare But Worth Checking

• Faulty Transmission Control Module (TCM): → Shop Transmission Assembly This is very rare. The TCM should only be suspected after all other possibilities have been exhaustively ruled out. On 6L80 transmissions, the TCM is part of the TEHCM assembly inside the pan, making it more susceptible to heat-related failure, but the pressure switch portion of the TEHCM is a much more common failure point.

Diagnosis Steps

1. Scan for Codes: Use an OBD-II scanner to confirm P0873 and check 🎬 See this quick breakdown of the P0873 diagnostic code. for any other related transmission codes, especially P0700.
2. Check Fluid: Inspect the transmission fluid level and condition. Ensure it is at the correct level and doesn't smell burnt or appear heavily contaminated. Low fluid can cause a loss of pump prime and set this code.
3. Inspect External Wiring: Visually inspect the main transmission wiring harness connector for corrosion, damage, or loose pins. A poor connection here can mimic internal faults.
4. Advanced Scan Tool Analysis: Use a scan tool capable of reading live transmission data. Monitor the status of the TFP switches. For a 'Circuit High' code, the PCM is seeing high voltage (e.g., 12V) when it expects low voltage (0V). The switch for circuit 'D' will not change its state as expected during shifting.
5. Drop Transmission Pan: If the external wiring is okay, the next step is to drain the fluid and remove the transmission oil pan to access the internal components.
6. Inspect Internal Components: Visually inspect the TFP manifold switch (4L60-E) or TEHCM (6L80) and its wiring for any signs of damage. For 6L80s, specifically look for torn, bubbled, or dislodged orange laminate pressure switch discs on the TEHCM.
7. Test the TFP Switch Circuit: Disconnect the component and test the resistance of the 'D' circuit. A 'Circuit High' code often corresponds to an open circuit (infinite resistance) or a short to voltage. Compare readings to the service manual specifications.
8. Replace Failed Component: Based on testing, replace the TFP manifold switch assembly (for 4L60-E), or replace the TEHCM/pressure switch repair plate (for 6L80). Remember that a new TEHCM requires programming.

Parts You'll Likely Need

• Transmission Fluid Pressure (TFP) Manifold Switch (4L60-E) (OEM #24215111) — This is the most common failure point for this code on the 4L60-E/4L65-E transmission. It contains the pressure switches that fail internally.
  Trusted brands: ACDelco, Dorman
  OEM price range: $70-$120
  Aftermarket price range: $40-$80
• Transmission Electro-Hydraulic Control Module (TEHCM) (6L80) (OEM #24256861) — For the 6L80 transmission, the pressure switches are integrated into this module. Often, the entire module must be replaced. It also requires programming to the vehicle.
  Trusted brands: ACDelco
  OEM price range: $300-$500
  Aftermarket price range: $200-$400
• TEHCM Pressure Switch Repair Kit (6L80) — As an alternative to replacing the entire TEHCM on a 6L80, aftermarket kits are available to replace just the failed laminate switch plate and seals. This is a more advanced repair but can be more cost-effective.
  Trusted brands: Sonnax, Superior
  Aftermarket price range: $30-$60

Related Codes That Often Appear With This One

• P0700 — This is a general Transmission Control System Malfunction code that is often set alongside more specific transmission codes like P0873 to indicate the TCM has requested the Check Engine Light.
• P0843 — This code is for 'Transmission Fluid Pressure Sensor/Switch 'A' Circuit High'. It's common to see multiple pressure switch codes together (e.g., P0843, P0877), indicating a failure of the entire manifold assembly or multiple membranes on the TEHCM.
• P0872 — This code is for 'Transmission Fluid Pressure Sensor/Switch 'D' Circuit Low'. Seeing opposite codes can point towards an intermittent wiring issue or a failing TFP manifold.
• P0751 — This code relates to 'Shift Solenoid 'A' Performance/Stuck Off'. Solenoid and pressure switch issues often occur together, especially on 6L80 transmissions where they are part of the same TEHCM assembly.

Technical Service Bulletins (TSBs) & Recalls

• TSB #PIP4379K (and later revisions like M/N): This bulletin lists P0873 among a large group of transmission codes that can cause a 'range inhibit' (no gear engagement) or other shifting problems. It suggests that issues like low fluid level, a loss of pump prime after service, or a cracked internal filter could be the cause. It advises technicians to check the fluid level properly and diagnose code P0701 first if it is present.

Platform-Specific Known Issues

• 4L60-E/4L65-E Manifold Switch Failure: On models with the 4-speed, the entire plastic pressure switch manifold assembly, which sits on the valve body, is the point of failure. It's a single, replaceable part. Owners report a sudden shift into limp mode (stuck in 3rd gear) as the primary symptom.
• 6L80 TEHCM Pressure Switch Membrane Failure: → Shop Transmission Valve Body On models with the 6-speed, the pressure switches are five small, orange, laminate discs on the TEHCM. These are known to tear or delaminate due to heat and fluid exposure. This is the direct cause of the P0873 code. While some attempt to repair just the membrane with a kit, many shops opt to replace the entire TEHCM, which then requires VIN programming.

Mechanic-Grade Diagnostic Values

• 6L80 Shift Solenoid (On/Off type) Resistance — expected: 20-40 Ohms. Failure: A reading outside this range indicates a failed solenoid coil.
• 6L80 Pressure Control Solenoid (PWM type) Resistance — expected: 3-8 Ohms. Failure: A reading outside this range indicates a failed solenoid coil.
• 6L80 TFP Switch State Test (on TEHCM) — expected: Should show a closed circuit (continuity) with no pressure applied.. Failure: When light pressure is applied (e.g., with a pencil eraser), the circuit should open (OL). If it stays closed or is always open, the switch is bad.
• TFP Sensor/Switch Signal Voltage — expected: The TCM expects to see low voltage (near 0V) when the switch is closed/on.. Failure: P0873 is set when the TCM sees high voltage (near 5V or 12V) when it expects low voltage. This indicates the switch is stuck open or there's a short to power.

Scan Tool Commands That Help

• Tech 2 or GDS2: Transmission Service Fast Learn — This stationary procedure must be performed after replacing the TEHCM or valve body. It allows the TCM to learn clutch fill times and pressure characteristics of the new components to ensure proper shift quality and prevent damage.
• Tech 2 or GDS2: Solenoid Automated Cleaning Process — If a solenoid performance DTC is present, this function cycles all solenoids to flush out potential debris before condemning the entire TEHCM.

Wiring & Ground Locations

• G110 — On the rear of the driver's side cylinder head. On some V8s, it may be on the right rear of the engine.. This is a critical ground point shared by the TCM and ECM. A loose or corroded connection at G110 can cause erratic behavior, communication loss codes, and incorrect voltage readings for various sensors, including the transmission pressure switches.
• Transmission Case Connector (C1/X1) — The main 16-pin or 23-way round connector on the side of the transmission case.. This is the pass-through for all electrical signals between the internal TEHCM/TFP switch and the vehicle's main wiring harness. Fluid intrusion, corrosion, or pushed-out pins in this connector can directly cause a 'Circuit High' fault.

Real Owner Repair Stories

• gm-trucks.com forum user (2009 GMC Sierra 1500 w/ 6L80) — Check engine light on, transmission stuck in what felt like 3rd gear (limp mode), harsh shifting.
  ❌ Tried (didn't work) Checked fluid level and condition (was clean and full)., Inspected external wiring harness (no visible damage).
  ✅ What actually fixed it The owner dropped the transmission pan and found the orange laminate discs on the TEHCM pressure switch plate were torn. He replaced the entire TEHCM assembly with a new ACDelco unit, had it programmed by a local shop, and performed a transmission service fast learn. This resolved the P0873 code and restored normal shifting.

OEM Part Supersession History

• 24252363, 24256670, 24257038 → 24256861, and later 19435614 — Hardware and software revisions to improve durability of pressure switches and solenoids and address heat-related failures.
  Heads up: TEHCMs are not backward or forward compatible. A 2010 TEHCM cannot be used in a 2007 truck, and vice-versa. The correct part must be ordered by VIN and programmed, as hardware and internal logic changed significantly between generations.

Model Year Variations Within This Range

• 2006-2008: These years primarily use the 4L60-E/4L65-E 4-speed. The fix involves replacing the separate TFP manifold switch (P/N 24215111), a relatively simple plastic component bolted to the valve body.
• 2009-2010: These years commonly use the 6L80 6-speed. The pressure switches are integrated into the TEHCM (P/N 24256861). The repair is more complex, requiring either replacement of the entire TEHCM (with programming) or a more intricate repair of the pressure switch laminate discs on the TEHCM itself.