P0877 on 2010-2017 GMC Terrain: Transmission Pressure Switch 'D' Circuit Low Causes and Fixes

What's Unique About the 2010-2017 GMC Terrain

The first-generation 6-speed automatic transmission (GM 6T70/6T75) used in this GMC Terrain is notorious for a specific internal failure that causes this code. The pressure switches inside the control module (TEHCM) rely on small, orange, laminated plastic discs to function. Over time, these discs are prone to deteriorating, cracking, or blowing out from exposure to hot transmission fluid, leading to a loss of pressure sensing and triggering codes like P0877. This is such a common issue that aftermarket repair kits are widely available specifically for this problem.

Symptoms You May Notice

• Harsh, banging, or delayed gear shifts
• Transmission getting stuck in one gear (limp mode)
• Check Engine Light is on
• Inability to shift into certain gears
• Flashing PRNDL display on the instrument cluster
• Vehicle struggles to accelerate or find the correct gear on slight inclines.

Most Likely Causes

1. Failed TEHCM Pressure Switch Laminated Discs 🔴 High Probability The laminated discs used in the original Gen 1 TEHCM (Transmission Electro-Hydraulic Control Module) are a well-documented failure point. They degrade from heat and fluid exposure over time, causing them to crack, deform, or blow out.
   How to confirm: After ruling out fluid and wiring issues, the TEHCM must be removed from the transmission for visual inspection. The damaged, dislodged, or missing orange discs are usually obvious upon inspection of the module. Resistance of the switch can be tested on the bench; it should be 0.5-10 ohms at rest and Open Loop (O.L.) when the switch is manually depressed.
   Typical fix: Replace the failed laminated discs and the rubber grommet seals with a dedicated repair kit (e.g., Sonnax 124740-30K). 🎬 Watch: Complete walkthrough of the TEHCM pressure switch repair. This is done on a workbench after the TEHCM is removed from the vehicle. The official GM repair is to replace the entire TEHCM assembly.
   Est. part cost: $25-$70
2. Low or Dirty Transmission Fluid ⚪ Low Probability
   How to confirm: Check the transmission fluid level and condition. These vehicles do not have a traditional dipstick; they use a fluid level check plug on the side of the transmission case. The check must be done with the engine running and the transmission at operating temperature (typically 180-200°F).
   Typical fix: Perform a transmission fluid drain-and-fill using DEXRON-VI certified fluid. If the fluid is very dark or has debris, it may indicate a more serious internal issue.
   Est. part cost: $60-$120
3. Failed Transmission Control Module (TEHCM) ⚪ Low Probability While the discs are the most common failure point, the TEHCM itself can fail electronically. This is less common than the disc failure.
   How to confirm: If the laminated discs are inspected and found to be intact and the wiring is good, the module itself may have an internal electronic fault. This requires advanced diagnostics with a scan tool that can communicate with the TCM and test switch electrical integrity. If the pressure switch resistance test fails (e.g., shows open at rest), the TEHCM has an internal electrical fault.
   Typical fix: Replace the entire TEHCM assembly. The new module must be programmed to the vehicle using specialized dealer-level equipment like GM's SPS2 software.
   Est. part cost: $400-$800
4. Wiring Harness or Connector Issue ⚪ Low Probability
   How to confirm: Inspect the main transmission wiring harness connector for corrosion, bent pins, or loose connections. Check the wiring for any signs of chafing or damage where it runs near the engine and transmission.
   Typical fix: Clean the connector pins or repair the damaged section of the wiring harness.
   Est. part cost: $10-$100

Diagnosis Steps

1. Check Transmission Fluid: Verify the fluid level is correct and the fluid is in good condition. This must be done via the check plug on the side of the transmission while the engine is running and warm.
2. Scan for Other Codes: Use an OBD-II scanner to check for other related transmission codes (like P0872, P0989) which strongly suggest the common TEHCM failure.
3. Inspect External Connector: Before opening the transmission, carefully inspect the main wiring harness connector at the transmission case for any signs of corrosion, moisture, or damaged pins.
4. Access and Remove TEHCM: If external checks pass, the next step is to access the TEHCM. This involves removing the airbox, battery, and battery tray to get to the transmission side cover.
5. Drain Fluid and Remove Side Cover: Drain the transmission fluid via the 11mm drain plug. Then, remove the bolts holding the transmission side cover to access the TEHCM.
6. Inspect Laminated Discs: Once the TEHCM is removed and on a workbench, visually inspect the four orange laminated pressure switch discs. Look for any that are cracked, deformed, or pushed out of place. The failure is usually obvious.
7. Repair or Replace: If the discs are damaged, replace them using a repair kit like the Sonnax 124740-30K. A special tool kit (like Sonnax 124740-TL70) is recommended for proper installation of the new discs and seals. If the discs look fine, the problem may be a more complex electronic failure within the TEHCM, which may require replacing the entire unit.

Parts You'll Likely Need

• Transmission Pressure Switch Laminated Disc & Seal Kit — This is the most common point of failure for code P0877 on this transmission. The kit contains the necessary replacement discs and seals to rebuild the pressure switch portion of the TEHCM.
  Trusted brands: Sonnax (P/N: 124740-30K), TransGo (P/N: PSR-5), Various aftermarket kits
  OEM price range: $400-$800 (For full TEHCM)
  Aftermarket price range: $25-$70 (For disc kit only)
• DEXRON-VI Automatic Transmission Fluid — You will lose 5-6 quarts of fluid when removing the TEHCM. The system must be refilled with the correct specification fluid.
  Trusted brands: ACDelco, Mobil 1, Valvoline
  OEM price range: $12-$18 per quart
  Aftermarket price range: $8-$15 per quart
• Pressure Switch Rebuild Tool Kit — While not strictly required, a tool kit is highly recommended to properly install the new seals and discs without damaging them.
  Trusted brands: Sonnax (P/N: 124740-TL70)
  OEM price range: N/A
  Aftermarket price range: $20-$40

Related Codes That Often Appear With This One

• P0872 — This code is for TFP Switch 'C' (or #3) Circuit Low. The laminated discs for multiple switches often fail around the same time, causing multiple pressure switch codes to appear together.
• P0989 — This code is for TFP Switch 'E' (or #5) Circuit Low. Like P0872, it is often triggered along with P0877 due to the common failure of the internal TEHCM switch discs.
• P0842 — This code is for TFP Switch 'A' (or #1) Circuit Low. This is another pressure switch code that can appear in combination with P0877 for the same reason: multiple failing discs.

Technical Service Bulletins (TSBs) & Recalls

• GM TSB PIP5025H: Discusses multiple transmission codes including P0872, P0877, and P0989. It points to inspecting the TEHCM for delamination of the pressure switch membranes, especially on vehicles with over 50,000 miles, and recommends replacing the TEHCM as the official repair.
• GM TSB 12-06-01-009D: While not for the transmission, this TSB is highly relevant for V6 owners as it addresses the widespread timing chain stretch issue by announcing updated service kits.
• GM TSB Bulletin #PIP4379N: Notes that a technician may find P0877 along with other codes like P0701 or P0843, which may result in a range inhibit condition; technicians are advised to follow published diagnostics for P0701 first.

Platform-Specific Known Issues

• The first-generation TEHCM (Transmission Electro-Hydraulic Control Module) in the 6T70/6T75 transmission is notorious for pressure switch laminated disk failures, making P0877 a very common code for this platform.
• GM issued several Technical Service Bulletins regarding these codes, including PIP5025H, which acknowledges the delamination of the pressure switch membranes as a cause.

Mechanic-Grade Diagnostic Values

• TFP Switch Resistance (Bench Test) — expected: 0.5 to 10 ohms (at rest, switch not depressed). Failure: Reading of O.L. (Open Loop) at rest, or a reading that does not change to O.L. when the switch is manually depressed with a non-conductive tool.
• TFP Switch State (Scan Tool Live Data) — expected: The switch state should change between 'HI' (no pressure) and 'LOW' (pressure applied) depending on the commanded gear.. Failure: For P0877, the scan tool data for TFP Switch 4 will be stuck 'LOW' even when the 1-2-3-4 clutch is in a low-pressure state (e.g., in 5th or 6th gear).
• TFP Switch 'D' Circuit Voltage — expected: A 'high' state is typically near battery voltage, while a 'low' state is near 0 volts.. Failure: The code sets when the voltage remains low (typically below 0.5 volts) when it should be high.

Scan Tool Commands That Help

• GDS2 / Tech2: Manual TFP Switch Test — With the TEHCM removed from the transmission but still electronically connected, a technician can gently press on each pressure switch diaphragm with a pencil eraser and watch the scan tool's TFP Switch State data. If the state for Switch #4 does not change from LOW to HI when pressed, it confirms a failed switch.
• GDS2 / Tech2: Service Fast Learn Adapts — After replacing the TEHCM or performing the disc repair, this procedure must be run to allow the TCM to relearn clutch volumes and ensure smooth shifting. This is a critical final step.
• GM SPS (Service Programming System): Replace and Reprogram — This function is required when a new TEHCM is installed. The new module must be programmed with the vehicle's specific calibration file to function. A used TEHCM can sometimes be 'cloned' by specialized services, transferring the original data to the replacement unit.

Wiring & Ground Locations

• TEHCM Main Connector — On the side of the transmission case, where the main vehicle harness connects to the internal transmission electronics.. This is the primary electrical interface. Corrosion or loose pins here can cause a variety of codes, including P0877. Power and ground for the entire module pass through this connector.
• G106 / G107 — G106 is often on the front center of the frame cross rail. G107 is often on the RH front of the frame.. These are cited in GM TSBs as primary grounds for the TCM. A poor ground connection can cause low voltage conditions and erratic behavior, mimicking an internal TEHCM fault.
• G104 / G110 — G104 is on the rear of the left cylinder head. G110 is on the rear of the right cylinder head.. These are primary engine-to-chassis grounds. Since the TEHCM grounds through the engine block and frame, a loose or corroded connection at these points can cause intermittent low voltage faults.

Real Owner Repair Stories

• Premier Automotive Diagnostics (YouTube/Reddit) (2012 Buick Enclave (with 6T70 transmission, identical TEHCM design)) — Intermittent shutter while shifting, Check Engine Light with codes P0877 and P0989.
  ❌ Tried (didn't work) Initial diagnosis suggested replacing the entire TEHCM assembly.
  ✅ What actually fixed it Upon removing the TEHCM, the technician found two of the four orange laminated pressure switch discs were ruptured and pushed out of their bores. The fix was to install an aftermarket pressure switch rebuild kit (new discs and seals), which resolved the codes and symptoms for a fraction of the cost of a new TEHCM.
• Fix & Maintain (YouTube) (Chevrolet Traverse (with 6T70 transmission)) — Hard shifting, Check Engine Light with pressure switch codes (P0872, P0877, P0878 mentioned as possibilities).
  ✅ What actually fixed it The video provides a step-by-step DIY guide for removing the TEHCM and replacing the failed laminated discs. The cause was confirmed to be two completely failed discs and a third that was torn. The repair using the aftermarket kit was successful.

OEM Part Supersession History

• 24256861 (TEHCM) → 19431596 (For some applications, verify with VIN) — Part update/revision.
  Heads up: The original TEHCM part number 24256861 went on a long-term, widespread backorder for an extended period. This caused the price of used modules to increase significantly and highlighted the need for the aftermarket disc repair kits. Always verify the correct part number for your specific VIN.

Model Year Variations Within This Range

• 2010-2012: These years were equipped with the 3.0L V6 engine.
• 2013-2017: For the 2013 model year, the 3.0L V6 was replaced by a more powerful 3.6L V6. While both use the 6T70/6T75 transmission, there may be slight variations in the TEHCM hardware or software calibrations between these engine applications. The laminated disc failure, however, is common to the Gen 1 TEHCM used across these years.

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• Premature Timing Chain Stretch (3.6L LFX & 3.0L LF1) 🔴 High — Very common, often appearing between 70,000 and 120,000 miles. Triggers codes P0008, P0017, P0018, P0019. (Ref: GM TSB 12-06-01-009D addresses the availability of updated timing chain kits for this issue.)
• Excessive Oil Consumption 🔴 High — Widespread issue, particularly noted in the 2.4L 4-cylinder but also reported by owners of the 3.0L V6. Can lead to low oil levels and potential engine damage if not monitored closely. (Ref: Special Coverage Adjustments (SCAs) were issued for some model years, primarily for the 2.4L engine, but the problem is known on the V6 as well.)
• StabiliTrak / Traction Control Service Light 🟠 Medium — Common complaint, often caused by faulty wheel speed sensors, corroded wiring to the hubs, or throttle body issues.
• Cracked Exhaust Manifold(s) 🟠 Medium — Can occur on the V6 engines, leading to an exhaust leak/ticking noise, especially when the engine is cold.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used TEHCM assembly is a very high-risk purchase and generally not recommended. The laminated discs are a known wear item, so a used part from a donor vehicle is likely to have the same issue or fail soon. The only time it might be considered is as a core for a specialist to rebuild, or if the original TEHCM is physically destroyed and its programming needs to be cloned by a specialty service.

Donor-vehicle mileage cap: roughly under 50000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Verify the donor vehicle was not in a major accident that could have damaged the transmission case.
• If possible, check the transmission fluid from the donor; dark, burnt fluid is a major red flag.
• Ask for the donor vehicle's VIN to check its service history if possible.

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

• Complete TEHCM Assembly: Due to the complex programming required (which links the part to the vehicle's VIN), a new OEM (ACDelco) or professionally remanufactured unit is the only reliable option if the entire module must be replaced.

Aftermarket brands forum-validated for this vehicle:

• Sonnax: Widely regarded as the top-tier choice for the pressure switch disc and seal repair kit (P/N: 124740-30K).
• TransGo: Another reputable brand offering a pressure switch repair kit (P/N: PSR-5).

Brands owners have reported issues with on this vehicle:

• Unbranded, low-cost disc repair kits: Forum and video comments suggest that some cheap, no-name kits use inferior disc material that may not withstand the pressure and heat, leading to a repeat failure in a short time.

Real Owner Stories

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

Related OBD-II Codes

• P0872 — Companion code for a different transmission fluid pressure switch. It frequently appears alongside P0877, strongly indicating the common TEHCM laminated disc failure as the root cause for both.
• P0989 — Another companion code for a transmission fluid pressure switch. Seeing P0989 together with P0877 is a classic symptom of the multiple pressure switch disc failure inside the TEHCM on this platform.
• P0008 — Indicates an engine position system performance bank 1 error. On this specific V6 engine, it is not related to the transmission fault but points to the other widespread issue: premature timing chain stretch.
• P0017 — Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor B). Like P0008, this code is a key indicator of the common timing chain issue in the 3.0L/3.6L V6 and is unrelated to the P0877 transmission problem.
• P0018 — Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A). This is another code that points directly to the well-documented timing chain stretch problem on these V6 engines, a separate issue from the TEHCM failure.

Frequently Asked Questions