P0873 on 2006-2010 Chevrolet Silverado: Transmission Pressure Switch Fixes

What's Unique About the 2006-2010 Chevrolet SILVERADO

The 2006-2010 Silverado spans two key generations with different transmissions, which changes the nature of this repair. Early models (2006-2007 'Classic') often have the 4-speed 4L60E/4L65E, where the TFP switch is a separate, common failure item. Later GMT900 models (2007.5-2010) increasingly used the 6-speed 6L80 transmission, where the pressure switches are integrated into the more complex and failure-prone Transmission Electro-Hydraulic Control Module (TEHCM) assembly. Knowing which transmission your truck has is critical for diagnosis and ordering the correct parts.

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 GMT800 generation (sold as the 'Classic' in 2007) and the beginning of the GMT900 generation (starting in 2007). GMT800s typically used the 4-speed 4L60E/4L65E. GMT900s introduced the 6-speed 6L80, especially in higher-trim or V8 models. The cause of P0873 is often a simple TFP switch on the 4-speed, but a more complex TEHCM issue on the 6-speed.

Symptoms You May Notice

• Check Engine Light is on
• Transmission stuck in one gear (limp mode, often 2nd or 3rd)
• Harsh, erratic, or delayed shifting
• Inability to shift into certain gears
• Flashing PRNDL or transmission warning light on the dash
• Code appears and limp mode engages only after the truck is fully warmed up (15-20 minutes of driving)

Most Likely Causes

1. Failed Transmission Fluid Pressure (TFP) Manifold Switch (4L60E) 🔴 High Probability → Shop Transmission Assembly The plastic and internal rubber diaphragms of the switch assembly, which is located inside the hot transmission, become brittle and fail over time from constant heat cycles, causing internal leaks or electrical faults. This is a well-documented failure on 4-speed GM transmissions.
   How to confirm: A key diagnostic clue is if the code and limp mode only appear after the transmission reaches operating temperature (15-20 mins). After dropping the transmission pan, the switch assembly is visible on the valve body. A 'Circuit High' code often points directly to a failed switch that is stuck open electrically.
   Typical fix: Replace the TFP manifold switch assembly. 🎬 Watch: Step-by-step guide to replacing the 4L60E pressure switch. This also requires replacing the transmission filter and pan gasket.
   Est. part cost: $50-$150 for 4L60E switch, $150-$400 for 6L80 TEHCM/switch manifold.
2. Failed Transmission Electro-Hydraulic Control Module (TEHCM) (6L80) 🔴 High Probability → Shop Transmission Assembly On 6L80 transmissions, the pressure switches are integrated into the TEHCM assembly. These modules are a known major failure point due to heat and vibration. The internal laminate substrate can delaminate or the switches themselves fail, causing a variety of pressure switch and solenoid codes, including P0873. Early 6L80 TEHCMs are particularly susceptible.
   How to confirm: This is often a process of elimination after confirming fluid and external wiring are good. The symptom of the fault only appearing when hot is a strong indicator of TEHCM failure. A professional scan tool can monitor switch states in real-time to confirm the 'D'/'C' circuit is reporting high voltage when it should be low.
   Typical fix: Replace the TEHCM assembly located on the valve body. The new TEHCM must be programmed with the vehicle's VIN using GM-specific software. It is often recommended to replace the entire module rather than attempting to repair individual components. 🎬 See how to rebuild and test 6L80 TEHCM circuits.
   Est. part cost: $250-$600
3. Damaged Internal Wiring Harness 🟡 Medium Probability The wiring inside the transmission is submerged in hot fluid and exposed to high temperatures, which can cause insulation to become brittle, chafe, or break over time, leading to a short to voltage.
   How to confirm: Visually inspect the wiring harness for damage, chafing, or burnt insulation after removing the transmission pan. Check for a secure connection at the TFP switch or TEHCM connector.
   Typical fix: Repair the damaged section of the harness or replace the internal harness if damage is extensive.
   Est. part cost: $50-$100

Rare But Worth Checking

• Contaminated or Low Transmission Fluid: → Shop Transmission Assembly While dirty fluid is more likely to cause mechanical issues or solenoid codes, severely degraded or low fluid can contribute to erratic electrical behavior and should be the first thing checked. TSB PIP4379N also notes a loss of pump prime after a fluid change can trigger this code.
• Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM): → Shop Transmission Assembly This is very rare. The module itself can fail and send false codes, but all other possibilities (wiring, sensors) should be exhausted before considering replacing the PCM/TCM.

Diagnosis Steps

1. Check the transmission fluid level and condition. Ensure it is full and does not smell burnt.
2. Use an OBD-II scanner to confirm P0873 and check for other transmission-related codes. 🎬 Watch: Understanding the P0873 circuit high diagnostic code. Note if P0700 is present.
3. Pay close attention to when the fault occurs. If it only happens after 15-20 minutes of driving, a heat-related component failure is highly likely.
4. Inspect the main external transmission wiring harness connector for damage, corrosion, or loose pins.
5. If external checks are okay, drain the transmission fluid and remove the oil pan.
6. Visually inspect the internal wiring harness for any signs of chafing, breaks, or damage.
7. Inspect the TFP manifold switch (on 4L60E) or TEHCM (on 6L80) for any visible signs of damage.
8. Using a multimeter, test the TFP switch circuit for a short to voltage, which is the typical cause of a 'Circuit High' code.
9. If the switch and wiring are suspect, replace the TFP manifold switch assembly (or TEHCM on 6L80 models).
10. For 6L80 models, follow the correct fluid refill procedure to avoid a no-move condition: add ~5 quarts, idle in neutral until the transmission is warm (~150-155°F), then check and top off fluid.

Parts You'll Likely Need

• Transmission Fluid Pressure (TFP) Manifold Switch (4L60E) (OEM #ACDelco 24215111) — This is the most common part to fail and directly cause code P0873 on 4-speed (4L60E/4L65E) models.
  Trusted brands: ACDelco, Delphi, Rostra
  OEM price range: $70-$120
  Aftermarket price range: $40-$80
• Transmission Electro-Hydraulic Control Module (TEHCM) (6L80) (OEM #24256657) — For 6-speed (6L80) models, the pressure switches are integrated into this module assembly, which is a known failure point. A new module is required and must be programmed. Note: Part number is for reference and should be verified with VIN.
  Trusted brands: ACDelco GM Genuine Parts
  OEM price range: $300-$500
  Aftermarket price range: $200-$350 (Remanufactured)
• Transmission Filter Kit (Filter and Pan Gasket) — The filter and pan gasket must be replaced anytime the transmission pan is removed for service.
  Trusted brands: ACDelco, ATP, Wix
  OEM price range: $30-$50
  Aftermarket price range: $15-$30
• Automatic Transmission Fluid (DEXRON-VI) — The correct fluid must be used to refill the transmission after service. All 2006 and newer GM transmissions use DEXRON-VI. A typical pan drop requires 6-8 quarts.
  Trusted brands: ACDelco, Valvoline, Castrol
  OEM price range: $8-$12 per quart
  Aftermarket price range: $6-$10 per quart

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 to be turned on. It will almost always be present with specific transmission codes like P0873.
• P0872, P0877, P0842, P0843 — These are other pressure switch codes for different circuits ('B', 'D', 'A'). When multiple appear together, it strongly points to a failure of the TFP manifold switch assembly, the TEHCM, or a shared wiring harness/connector.

Technical Service Bulletins (TSBs) & Recalls

• TSB #PIP4379K (and newer revisions like M/N): This is a broad GM bulletin covering numerous transmission codes, including P0873. It notes that these codes can appear due to a loss of pump prime after a fluid service or long periods of storage. It advises that if code P0701 is also present, its diagnostic procedure should be followed first.
• TSB #PIP5378: While for slightly later models with Allison transmissions, its logic is relevant. It addresses a 'stuck in one gear' condition with codes including P0873 and directly recommends replacing the Pressure Switch Manifold (PSM) if other diagnostics do not resolve the issue, providing the OEM part number.

Platform-Specific Known Issues

• On 6L80-equipped trucks, a failed TEHCM replace

Mechanic-Grade Diagnostic Values

• TFP Sensor/Switch Signal Voltage (Circuit High Condition) — expected: Normally 0V when the switch is closed (pressure applied) and ~5V or battery voltage when open (no pressure).. Failure: A 'Circuit High' code P0873 is set when the TCM sees high voltage (near 5V or battery voltage) when it expects to see low voltage (near 0V) for that gear. This indicates the switch is stuck open or there is a short to power.
• 6L80 TEHCM Pressure Switch Continuity Test (Switch Removed) — expected: The switches are normally closed. You should have continuity (near 0 Ohms) across the switch terminals when no pressure is applied.. Failure: If you press down on the switch plunger and the circuit does not open (resistance remains near 0), the switch is faulty.
• 6L80 Pressure Control Solenoid (PCS) Resistance — expected: 3.0 - 5.5 Ohms at 70°F (21°C).. Failure: A reading outside this range indicates a faulty solenoid coil.
• 4L60E Pressure Control (EPC) Solenoid Resistance — expected: 3.5 - 8.0 Ohms at 68°F.. Failure: A reading outside this range indicates a faulty solenoid coil.

Scan Tool Commands That Help

• Tech 2 / GDS2: Live Data - TFP Switch State — To monitor the real-time status (On/Off or High/Low) of each pressure switch while the vehicle is running. For P0873, you would watch the TFP Switch 'D' or 'C' parameter. If it reads 'High' or 'Off' when the transmission is commanded into a gear where that switch should be 'Low' or 'On', it confirms the fault.
• GM SPS2 / Techline Connect: TEHCM Programming and Setup — This is a mandatory step after replacing the TEHCM on a 6L80 transmission. The new module must be programmed with the vehicle's VIN and specific calibration files to communicate with the rest of the vehicle and function correctly.

Wiring & Ground Locations

• 16-Way Case Connector (6L80) — The main round electrical connector on the passenger side of the 6L80 transmission case. It connects the external vehicle harness to the internal TEHCM.. This is the primary interface between the TCM (inside the TEHCM) and the rest of the vehicle. Corrosion or damage to the pins or the pass-through sleeve seal can cause a wide range of electrical faults, including P0873.
• TCM Connector J2 (Allison Transmission) — On trucks equipped with the Allison transmission (HD models), this is the RED connector of the two main TCM connectors.. Pin 3 (typically a WHITE wire) is the signal input from the pressure switch that sets P0873. Pin 20 (typically a GREEN wire) is the sensor ground. These are the primary test points at the module to check for harness faults.

Real Owner Repair Stories

• Codemansauto YouTube Channel (via Go-Parts.com) (Chevrolet Silverado HD with Duramax/Allison) — Check engine light with a pressure switch code (P0875, related to P0873) and transmission in limp mode.
  ❌ Tried (didn't work) The diagnosis avoided trial-and-error parts replacement.
  ✅ What actually fixed it The problem was resolved by replacing the internal Transmission Fluid Pressure Switch Manifold. The key diagnostic clue was that the truck could be driven for 15-20 miles before the fault occurred, pointing to a heat-related failure of the switch assembly.

OEM Part Supersession History

• Early Gen 1 6L80 TEHCM (various PNs) → 24256657 (and later revisions) — Early TEHCMs were prone to pressure switch failures and issues from heat. Later designs featured improved solenoids and an updated pressure manifold gasket for better durability.
  Heads up: While physically similar, TEHCMs have different internal calibrations and sometimes different connector styles (early black vs. later grey). A new TEHCM must be programmed to the vehicle's VIN to function.

Model Year Variations Within This Range

• 2006-2009 (6L80): These early 6L80 transmissions often used a 'Gen 1' TEHCM which is known to have a higher failure rate for the integrated pressure switches. They may also use a black 20-pin connector.
• 2010 (6L80): Later model year 6L80s may have an updated TEHCM design with improved internal components and potentially a grey 20-pin sealed connector, offering better reliability than the earliest versions.