P0740 on 2020-2025 Hyundai Palisade: Torque Converter Clutch Circuit Malfunction Causes and Fixes

What's Unique About the 2020-2025 Hyundai Palisade

The first-generation Hyundai Palisade uses an A8LF2 8-speed automatic transmission, which it shares with the Kia Telluride. While P0740 itself is a generic code, its appearance on this platform is very commonly associated with a specific failure pattern. Hyundai has issued Technical Service Bulletin 22-AT-005H for closely related codes like P0741 (TCC Stuck Off), which instructs dealers to replace the responsible solenoid *and* the entire internal valve body wiring harness. This indicates a known weakness in these internal components, a conclusion supported by owner experiences on forums. The issue is also prevalent on its platform-mate, the Kia Telluride.

Symptoms You May Notice

• Check Engine Light is on
• Reduced fuel economy
• Engine RPMs fluctuate or surge while cruising at a steady speed (shuddering)
• Vehicle may feel like it's slipping or has a loss of power
• Harsh or delayed gear shifts
• Inability to shift into the highest gear
🎬 Watch: Understanding the P0740 code and how to fix it
• Transmission may feel like it's not 'locking' into gear on the highway

Most Likely Causes

1. Faulty Torque Converter Clutch (TCC) Solenoid and/or Valve Body Harness 🔴 High Probability → Shop Automatic Transmission Torque Converter Hyundai has issued a TSB (22-AT-005H) that instructs technicians to replace the solenoid and the internal valve body harness for related fault codes, indicating this is a recognized failure pattern on the Palisade's A8LF2 transmission. This suggests a high failure rate for one or both components.
   How to confirm: A technician will use a scan tool to monitor TCC slip speed and command the solenoid on/off. If the solenoid doesn't respond or the circuit shows an open/short on a multimeter 🎬 See how to test solenoids on this 8-speed transmission, and external wiring is okay, the fault is internal. The valve body must be removed for direct testing or replacement.
   Typical fix: Replace the torque converter clutch solenoid and the internal valve body wiring harness (Part No. 46307-4G100) as per TSB 22-AT-005H. This requires draining the fluid and removing the transmission pan and valve body. 🎬 Watch: Step-by-step guide to removing the transmission valve body
   Est. part cost: $150-$300
2. Low or Dirty Transmission Fluid 🟡 Medium Probability → Shop Transmission Assembly
   How to confirm: Check the transmission fluid level and condition. The fluid should be at the correct level, pink/red in color, and not smell burnt. Dark, burnt, or fluid with clutch material indicates a problem. Low fluid can cause pressure issues, while dirty fluid can clog solenoid passages.
   Typical fix: Perform a transmission fluid drain-and-fill or a full fluid exchange using Hyundai-specific SP4-M fluid. If the fluid is very contaminated, the component that caused the contamination (like a failing clutch or solenoid) must also be addressed.
   Est. part cost: $80-$200
3. Damaged External Wiring or Connectors ⚪ Low Probability
   How to confirm: Visually inspect the wiring harness leading to the transmission for any signs of damage, corrosion, or loose connections at the main plug. Test for continuity and voltage at the connector pins corresponding to the TCC solenoid circuit using a multimeter and a factory wiring diagram.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the corroded connector.
   Est. part cost: $20-$100

Rare But Worth Checking

• Failing Torque Converter: → Shop Automatic Transmission Torque Converter While the code points to an electrical circuit, a mechanical failure within the torque converter's clutch can sometimes cause symptoms that lead to this code. This is usually a last resort after solenoids and wiring have been checked.
• Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM): → Shop Engine Control Module (ECM) It is very rare for the control module itself to fail. This should only be considered after all other possibilities (fluid, wiring, solenoids, valve body) have been exhaustively ruled out.

Diagnosis Steps

1. Connect an OBD-II scanner to confirm the P0740 code and check for any other pending or active transmission codes, especially P0741 or P0743.
2. Check the transmission fluid level and condition. Low, dark, or burnt-smelling fluid can cause or indicate serious issues.
3. Inspect the external transmission wiring harness and main connector for any visible damage, corrosion, or loose pins.
4. Use an advanced scan tool to monitor live data, specifically Engine RPM, Transmission Input Speed RPM, and TCC Slip Speed. Command the TCC solenoid on and off to see if the circuit responds and if slip RPM changes.
5. If the solenoid does not respond or the circuit shows open/short, and external wiring is good, the problem is internal to the transmission.
6. Following Hyundai TSB 22-AT-005H, the next step is to drain the fluid, remove the transmission oil pan, and remove the valve body.
7. Replace the torque converter clutch solenoid and the valve body wiring harness (Hyundai P/N: 46307-4G100).
8. Reinstall the valve body, pan, and refill with the correct specification of Hyundai transmission fluid (SP4-M).
9. Clear the codes and perform a road test to verify the repair.

Parts You'll Likely Need

• Valve Body Wiring Harness (OEM #46307-4G100) — Hyundai's TSB explicitly calls for replacing this harness along with the solenoid, suggesting it's a primary and common point of failure for this code. This part number is confirmed to fit the Palisade.
  Trusted brands: Hyundai (OEM)
  OEM price range: $100-$145
• Torque Converter Clutch Solenoid — This solenoid is the most likely electrical component to fail inside the transmission, causing the P0740 code. Hyundai's TSB for related codes recommends its replacement.
  Trusted brands: Hyundai (OEM)
  OEM price range: $80-$150
  Aftermarket price range: $50-$100
• Automatic Transmission Fluid (ATF) (OEM #SP4-M (or SP-IV-M)) — The transmission must be drained to perform the repair. It must be refilled with fluid meeting Hyundai's SP4-M specification. Approximately 5-6 quarts are needed for a pan drop.
  Trusted brands: Hyundai (OEM), Idemitsu, ENEOS
  OEM price range: $20-$30 per quart
  Aftermarket price range: $12-$20 per quart

Related Codes That Often Appear With This One

• P0741 — P0741 indicates 'TCC System Stuck Off'. It's a performance code for the same system, often caused by the same faulty solenoid or harness. TSB 22-AT-005H directly addresses this code.
• P0743 — P0743 indicates 'TCC Solenoid Circuit Electrical'. This is a more specific electrical code for the same circuit and is also covered by the same Hyundai TSB.

Technical Service Bulletins (TSBs) & Recalls

• 22-AT-005H (supersedes 20-AT-005H-1): Addresses DTCs P074100, P074300, and others by recommending the replacement of the related solenoid and valve body harness on Palisade (LX2) and other models.

Platform-Specific Known Issues

• Hyundai has issued Technical Service Bulletin 22-AT-005H, which covers the Palisade (LX2) for various transmission solenoid DTCs. It advises replacing the faulty solenoid and the valve body harness (P/N 46307-4G100), pointing to a known weakness in these internal components.
• The issue is not isolated to the Palisade; its corporate cousin, the Kia Telluride, which shares the A8LF2 transmission, also suffers from the same torque converter shudder and related diagnostic codes.

Mechanic-Grade Diagnostic Values

• Torque Converter Clutch (TCC) Solenoid Resistance — expected: 5.3 ± 0.3 Ohms. Failure: A reading that is significantly higher (open circuit) or lower (short circuit) than the specified range.

Scan Tool Commands That Help

• Hyundai GDS (Global Diagnostic System): Resetting Auto T/A values (Reset PCM/TCM Adaptive Values) — This function must be used after replacing the transmission, valve body, or solenoids to erase old learned shift parameters.
• Hyundai GDS (Global Diagnostic System): Adaptive Learning Procedure (Drive Cycle) — Immediately after resetting the adaptive values. The technician must perform a specific drive cycle, accelerating and decelerating through the gears multiple times, to allow the TCM to relearn proper shift points.
• Advanced OBD-II Scanner / GDS: TCC Solenoid Bidirectional Control — During diagnosis to manually command the TCC solenoid on and off while monitoring live data (like TCC slip RPM) to verify if the solenoid is responding to commands from the TCM.

Wiring & Ground Locations

• TCC Solenoid Circuit Test Pins — At the main transmission case connector.. To test the TCC solenoid's resistance without removing the transmission pan, you can measure between Pin 14 and Pin 1 of the main connector. This quickly isolates whether the fault is in the internal wiring/solenoid or external to the transmission.
• Transmission Ground Cable — Typically located on the top of the transmission case, under the battery tray.. A poor ground connection for the transmission can cause a variety of electrical faults and erratic behavior from sensors and solenoids. Ensuring this ground is clean and tight is a crucial step in diagnosing any transmission electrical code.

Model Year Variations Within This Range

• 2020-2025: The Palisade received a significant facelift for the 2023 model year, but these changes were primarily cosmetic and technological. The 3.8L V6 engine and A8LF2 8-speed automatic transmission were carried over without major changes, so the diagnosis and repair for code P0740 remain consistent across the entire 2020-2025 generation.

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• Tow Hitch Wiring Harness Fire Risk 🔴 High — Affects a large number of 2020-2022 models equipped with an accessory tow hitch. The recall was widespread to cover all potentially affected vehicles. (Ref: NHTSA Recall (multiple, including one noted in Aug 2022). Owners are advised to park outdoors until the repair is complete.)
• Windshield Wiper Motor Failure 🔴 High — Common on 2020-2023 models, especially when wipers are obstructed by snow or ice, causing the motor's internal circuit breaker to trip or fail entirely. (Ref: NHTSA Campaign Number 22V630000; Hyundai Recall 228. The recall was later expanded.)
• Foul Interior Odor From Headrests 🟡 Low — Reported in early model years (primarily 2020-2021) on Limited and Calligraphy trims with Nappa leather. Described as a chemical, garlic, or old socks smell. (Ref: Not a formal recall, but Hyundai issued a service procedure for dealers to clean or replace the headrests to resolve the odor.)
• Transmission Shudder/Vibration 🟠 Medium → Shop Transmission Assembly — Some owners report a shudder or vibration, particularly during low-speed acceleration or when shifting into 2nd gear, even without a Check Engine Light. This can be a precursor to the P0740/P0741 fault. (Ref: Related to TSB 22-AT-005H if a code is present.)
• Idle Stop & Go Oil Pump Fire Risk 🔴 High — A recall was issued for 2023-2024 models where the electric oil pump controller for the Idle Stop & Go system could overheat due to damaged components. (Ref: NHTSA recall 23V526.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this specific repair, using used parts is strongly discouraged. The only exception might be for an external component like the main transmission wiring connector if a new pigtail is unavailable and the original is physically damaged.

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

• Valve Body Wiring Harness (46307-4G100)
• Torque Converter Clutch (TCC) Solenoid

Brands owners have reported issues with on this vehicle:

• Any non-OEM brand for internal transmission electrical components like the harness or solenoids. The high labor cost of accessing these parts makes the risk of using unverified aftermarket parts financially unwise. The issue is linked to a specific Hyundai TSB, making the OEM-revised part the most reliable choice.

Real Owner Stories

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

Related OBD-II Codes

• P0741 — Often appears with P0740; specifically indicates Torque Converter Clutch (TCC) System Performance or Stuck Off, frequently cited in TSB 22-AT-005H.
• P0743 — A companion code indicating an electrical circuit issue with the Torque Converter Clutch system, also covered under the same TSB for solenoid and harness replacement.
• P074100 — The specific extended diagnostic code format used in Hyundai TSB 22-AT-005H to identify TCC performance failures in the Palisade's A8LF2 transmission.
• P074300 — The extended diagnostic code for TCC electrical failure mentioned alongside P074100 in Hyundai technical service bulletins for the Palisade.

Frequently Asked Questions