P0877 on 2008-2017 Buick Enclave 3.6L: Transmission Pressure Switch Causes and Fixes

What's Unique About the 2008-2017 Buick Enclave

The Buick Enclave uses a GM 6T75 automatic transmission, which has a well-documented design issue with the pressure switches in the Gen 1 TEHCM. These switches are not traditional sensors but rely on small, orange, laminated plastic discs that act as diaphragms. Over time and with exposure to heat cycles and transmission fluid, these discs become brittle, causing them to crack, delaminate, or blow out. This breach prevents the switch from reading pressure correctly and triggers code P0877, often along with other pressure switch codes like P0989.

Symptoms You May Notice

• Check Engine Light is on
• Harsh, erratic, or delayed gear shifts
• Transmission slipping between gears
• Vehicle stuck in one gear (limp mode or failsafe mode)
• Inability to shift into certain gears
• Shuttering or jerking during shifts
• No reverse gear

Most Likely Causes

1. Failed Pressure Switch Laminate Discs in TEHCM 🔴 High Probability The plastic diaphragms used in the Gen 1 6T75 TEHCM are a known failure point. They become brittle with age and exposure to transmission fluid and heat, causing them to crack or break. This is the most common cause for P0877 on this platform by a wide margin.
   How to confirm: After removing the TEHCM from the transmission, visually inspect the small, orange laminate discs. They will often be visibly cracked, broken, or pushed out of their bores. Multiple discs are frequently found damaged at the same time.
   Typical fix: Remove the TEHCM and replace the damaged laminate discs and seals using a specialized rebuild kit. This is a bench repair performed on the removed module. 🎬 See this walkthrough of repairing failed pressure switches on the TCM. This avoids the high cost and programming requirements of a new TEHCM.
   Est. part cost: $25-$50

Rare But Worth Checking

• Failed TEHCM (Electrical Failure): While far less common than the laminate disc failure, the TEHCM itself can fail electrically. If the laminate discs are intact upon inspection, the module itself may be faulty. This requires replacing the entire TEHCM and programming it to the vehicle's VIN.
• Wiring Harness Issue: A short to ground or open in the wiring harness between the main connector and the TEHCM could theoretically cause this code, but it is much less likely than the internal TEHCM failure. A visual inspection of the harness and connector is still a valid diagnostic step.
• Low Transmission Fluid Level/Pressure: Extremely low fluid could cause erratic pressure readings, but it would typically set other codes first and present with more severe slipping symptoms. This is not a primary cause for an isolated P0877.

Diagnosis Steps

1. Confirm the presence of P0877 and any other transmission codes using a capable OBD-II scanner. Note any accompanying codes like P0989, P0872, etc.
2. Check the transmission fluid level and condition. The fluid should be at the correct level and not smell burnt or contain excessive metal particles. Note: This is a preliminary check; low fluid is not the likely root cause for this specific code.
3. Given the extremely high probability of TEHCM disc failure on the 6T75 transmission, the most practical next step is to plan for the removal of the transmission side cover and the TEHCM.
4. Once the TEHCM is removed from the valve body, carefully inspect the five pressure switch laminate discs. Look for cracks, breaks, or any discs that are dislodged from their bores.
5. If the discs are damaged, the diagnosis is confirmed. Proceed with the repair using a rebuild kit.
6. If the discs are surprisingly intact, the issue may be an electrical failure within the TEHCM itself or a wiring problem, which requires more advanced electrical diagnostics with a multimeter to check for shorts or opens in the circuit.

Parts You'll Likely Need

• TEHCM Pressure Switch Rebuild Kit — This is the most common and cost-effective fix. It contains the new laminate discs and seals required to repair the pressure switches on the original TEHCM.
  Trusted brands: Sonnax (P/N: 124740-30K), TransGo
  Aftermarket price range: $25-$50
• DEXRON-VI Automatic Transmission Fluid — You will lose several quarts of fluid when removing the transmission side cover and TEHCM. The system must be refilled to the proper level with the correct fluid.
  Trusted brands: ACDelco, Valvoline, Castrol
  OEM price range: $25-$35 per gallon
  Aftermarket price range: $20-$30 per gallon
• Transmission Valve Body Cover Gasket (OEM #ACDelco 24236923 (verify by VIN)) — The side cover gasket should be replaced to prevent leaks upon reassembly.
  Trusted brands: ACDelco, Fel-Pro, Mahle
  OEM price range: $20-$40
  Aftermarket price range: $15-$30
• Remanufactured TEHCM Assembly (OEM #24256861, 24261875, 24275870 (examples, verify by VIN)) — Needed only if the original TEHCM has an unrepairable electrical fault or if you prefer to replace the entire unit instead of repairing it. Requires programming to the vehicle's VIN.
  Trusted brands: ACDelco (Reman), Dorman (P/N: 609-000)
  OEM price range: $300-$500
  Aftermarket price range: $250-$450 (plus core charge)

Related Codes That Often Appear With This One

• P0989 — This is for 'Transmission Fluid Pressure Switch 5 Circuit Low'. It is extremely common to see P0877 and P0989 together, as the laminate discs for multiple switches often fail around the same time.
• P0872 — This is for 'Transmission Fluid Pressure Switch 3 Circuit Low'. Like P0989, it points to the same common failure of the TEHCM pressure switch diaphragms.
• P0842 — This is for 'Transmission Fluid Pressure Switch 1 Circuit Low'. Seeing multiple pressure switch codes together is a strong confirmation of the internal TEHCM disc failure.

Technical Service Bulletins (TSBs) & Recalls

• PIP4379K: Addresses various shift and range inhibit issues, often pointing to hydraulic circuit problems within the TEHCM.
• PIP5100A: Mentioned in relation to multiple pressure switch codes appearing together, pointing to TEHCM failure.

Platform-Specific Known Issues

• A known TSB (Technical Service Bulletin), such as PIP4379K, addresses various shift quality issues and codes, including P0877, related to the TEHCM and hydraulic system in these transmissions.

Mechanic-Grade Diagnostic Values

• TFP Switch State (High/Low) — expected: The switch parameter should toggle between High and Low state on a scan tool when shifting between gears (e.g., 2nd and 5th).. Failure: The TFP Switch 4 parameter is stuck in the 'Low' state and does not toggle when commanded to a gear that should read 'High'.
• DTC Set Condition — expected: The TCM detects the TFP switch 4 signal voltage remains LOW after the 1-2-3-4 clutch transitions from a HIGH pressure state to a LOW pressure state. The DTC sets when 12-18 counts are accumulated.. Failure: Accumulation of fault counts leading to the DTC being set.

Scan Tool Commands That Help

• GDS2 / Tech2: TFP Switch State Display — This is the primary live data parameter to monitor. While driving or using shift commands, a technician can watch the state of TFP Switch 4. If it is stuck 'LOW' when it should be 'HI' (e.g., in 5th gear), it strongly indicates a fault in that switch's circuit.
• GDS2 / Tech2: Transmission Adaptive Values Learn — This procedure is mandatory after replacing the TEHCM or performing internal transmission repairs. It allows the TCM to learn the hydraulic characteristics of the clutches. Failure to perform this can result in poor shift quality and new DTCs being set.
• GDS2 / Tech2: Service Programming System (SPS) — This is used to program a new or remanufactured TEHCM to the vehicle. The module must be programmed with the correct VIN and the latest software calibrations from GM.

Wiring & Ground Locations

• Main Transmission Connector (X107/J107) — The 20-way external connector on the transmission side cover where the vehicle harness attaches to the TEHCM.. This is the single point of electrical connection for the entire TEHCM. Corrosion, moisture, or bent/loose pins in this connector can cause low voltage faults like P0877 before the signal even gets to the module.
• G113 — Located on the left side of the engine, at the engine-to-transmission stud.. This is a primary ground point for the transmission assembly. A poor connection here can cause erratic behavior and electrical noise, potentially affecting the TEHCM's operation and sensor readings.
• G105 — On the rear of the engine compartment, on the left middle of the instrument panel bulkhead.. This ground point serves various components in the engine compartment. While not exclusive to the transmission, poor grounding here can contribute to general electrical issues on the vehicle that could manifest as sensor faults.

Real Owner Repair Stories

• YouTube video by 'Premier Automotive Diagnostics' (2012 Buick Enclave) — Intermittent shutter while shifting, Check Engine Light on with codes P0877 and P0989.
  ❌ Tried (didn't work) The vehicle was brought directly to the shop for diagnosis; no prior failed repairs were mentioned.
  ✅ What actually fixed it The technician removed the transmission side cover and the TEHCM. Visual inspection confirmed two of the orange laminate pressure switch discs were ruptured and pushed out of their bores. The technician used a special tool kit (similar to Sonnax 124740-TL30) to remove the old discs and seals and install a new set from a rebuild kit. This repaired the TEHCM without replacing the entire expensive unit.

OEM Part Supersession History

• 24256861 → 24261875, 24275870, 19434978 (example chain, verify by VIN) — GM has released multiple revisions of the TEHCM to address reliability and performance issues. Newer part numbers often contain updated hardware and require the latest software programming.
  Heads up: A new TEHCM must be programmed to the vehicle's VIN using GM's Service Programming System (SPS). They are not plug-and-play.

Model Year Variations Within This Range

• 2008-2012 (approx.): These model years are equipped with the Gen 1 6T75 transmission, which uses a TEHCM with five laminate disc pressure switches. These are the vehicles susceptible to the common P0877 failure due to cracked discs.
• 2013-2017 (approx.): Starting around 2013, GM began phasing in the Gen 2 6T75 transmission. The Gen 2 TEHCM does not use pressure switches; it uses a 'clutch pulse learning' process instead. Therefore, a Gen 2 transmission will not set a P0877 code for a failed pressure switch. The transition occurred across 2013-2014, so it's critical to identify the transmission generation (via RPO code or visual inspection) on a 2013 model.

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 🔴 High — Very common, especially on 2008-2012 models, often appearing between 40,000 and 120,000 miles. Triggers codes like P0008, P0017, P0019. (Ref: TSB #12-06-01-009F, Special Coverage #11340C (expired))
• Power Steering Pump/Rack Failure 🟠 Medium — Widespread issue causing loss of power steering assist, particularly at low speeds. (Ref: Special Coverage #14329B (10 years/150,000 miles))
• Water Leaks into Cabin 🟠 Medium — Commonly caused by clogged sunroof drain tubes or A/C evaporator drains, leading to wet passenger floorboards and potential electrical issues.
• Broken 3-5-R Wave Plate 🔴 High — A known issue primarily on earlier 2007-2009 models, causing loss of 3rd, 5th, and Reverse gears. Less common than TEHCM failure but requires a transmission rebuild. (Ref: Special coverage was issued but has since expired.)
• Failing Ignition Coils 🟡 Low — Fairly common failure leading to engine misfires (P030x codes). Relatively easy to diagnose and replace.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this specific repair, a used part is almost never a smart choice for the main component (TEHCM). The only used parts that could be considered are simple hard parts like the transmission side cover if it were damaged during removal.

What to inspect on the donor part:

• For a TEHCM, there are no reliable visual cues. A used Gen 1 TEHCM has the same inherent design flaw as the one that failed, regardless of mileage. It is considered a ticking time bomb.

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

• Remanufactured TEHCM: While aftermarket options exist (like Dorman), the safest bet is a Genuine GM/ACDelco remanufactured unit to ensure compatibility and access to correct programming. This is only necessary if the original TEHCM has an electrical fault beyond the repairable discs.

Aftermarket brands forum-validated for this vehicle:

• TEHCM Rebuild Kit: Sonnax (P/N: 124740-30K) and TransGo (P/N: PSR-5) are the two most trusted and widely used brands for the pressure switch laminate disc and seal repair kits.

Brands owners have reported issues with on this vehicle:

• Unknown/unbranded TEHCM rebuild kits or remanufactured TEHCMs from obscure online sellers. The quality of the laminate discs and seals is critical, and a failed repair will require re-doing the entire labor-intensive job.

Real Owner Stories

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

Related OBD-II Codes

• P0989 — Transmission Fluid Pressure Switch 'E' Circuit Low. This code frequently appears with P0877 because it relates to another pressure switch on the same TEHCM assembly. The laminate discs for multiple switches often fail at the same time.
• P0872 — Transmission Fluid Pressure Switch 'C' Circuit Low. Like P0989, this is a common companion code indicating that another of the five pressure switch diaphragms in the TEHCM has failed.
• U0101 — Lost Communication with TCM. This code can appear alongside P0877 if the TEHCM has an internal electrical failure, rather than just the mechanical failure of the laminate discs, causing it to stop communicating with other vehicle modules.

Frequently Asked Questions