P0740 Code: Toyota Tacoma (2016-2023) - Causes, Symptoms & Fixes

Here is a comprehensive diagnostic guide for P0740 (Torque Converter Clutch Circuit Malfunction) as it applies to the 2016-2023 Toyota Tacoma. Note on data: In the provided NHTSA data, there are no owner complaints for this issue on this model/year, and there are no recalls listed. Therefore, this guide uses general automotive knowledge for the technical content and acknowledges the data limitations.

CODE MEANING AND SEVERITY

• What P0740 means

  • P0740 = Torque Converter Clutch Circuit Malfunction. The torque converter clutch (TCC) is not signaling or engaging properly, or the control circuit for the TCC is out of specification. When the TCC cannot lock up correctly, you may feel slipping, higher engine rpm, or inconsistent shifting.

• How it affects the Tacoma

  • Driveability can be affected: you may experience transmission slipping, lack of fuel economy benefit from lockup, harsh or delayed shifts, or the MIL (Check Engine Light) being on.
  • If left unresolved, repeated overheating or clutch wear can occur, potentially shortening transmission life. In some cases the vehicle may enter a fail-safe or limp mode to protect the transmission.

• Severity rating (practical)

  • Moderate: Not usually an immediate safety risk, but the problem can worsen, affect reliability and fuel economy, and may lead to more expensive repairs if ignored.

COMMON CAUSES ON TOYOTA TACOMA

• Faulty TCC solenoid or its circuit

  • A failing solenoid, poor electrical connection, or damaged wiring harness can prevent the TCC from engaging or disengaging correctly.

• Wiring harness, connectors, or grounds

  • Corroded connectors, loose pins, or damaged insulation around the valve body area or TCC wiring can cause intermittent or persistent failure.

• Transmission fluid quality or level

  • Low fluid level, dirty/contaminated ATF, or incorrect ATF specification can hinder TCC operation and valve body performance.

• Valve body or clutch-related wear

  • Worn clutch packs, varnished valve body passages, or debris in the valve body can cause improper TCC operation.

• Torque converter issues

  • A worn or damaged torque converter itself can contribute to lockup problems even if the solenoid is functioning.

• Transmission control module (TCM) or powertrain control software

  • Software calibration or a need for an update can affect TCC command and performance.

• Miscellaneous contributing factors

  • Excessive heat in the transmission or towing beyond spec can accelerate wear and affect TCC operation.

SYMPTOMS

• MIL illuminated with P0740 or multiple related codes
• Inconsistent or no TCC lockup, especially at highway cruising speeds
• Slipping or shuddering during steady cruising
• Harsh or delayed shifts
• Higher than normal RPM at a steady speed (loss of lockup)
• Increased fuel consumption
• Transmission may overheat or enter a limp/limited operation mode if the issue is persistent

DIAGNOSTIC STEPS

Note: These steps are designed to be practical for DIYers with a capable scanner, but some steps (especially pressure testing and valve-body service) are best done by a professional.

Step 0: Prepare

• Retrieve DTCs with a capable OBD-II scanner. Confirm P0740 as the primary code and note any related codes (P0741, P0742, P077x, P0700, etc.).
• Note vehicle mileage, recent transmission service history, and driving patterns (towing, heavy loads, short trips).

Step 1: Basic checks

• Check transmission fluid level and condition (color, odor, amount). Look for contamination (metallic bits, burnt smell). Transmission fluid that is low or degraded can trigger TCC-related issues.
• Confirm ATF type matches Toyota’s specification for the Tacoma (do not mix fluids). If the fluid is dirty or smells burned, plan a replacement.

Step 2: Visual and electrical inspection

• Inspect electrical connectors to the transmission, especially the TCC solenoid and valve body harnesses. Look for bent pins, corrosion, or damaged wires.
• Check for any obvious leaks around the transmission pan, cooler lines, or valve body area.

Step 3: Live data and basic electrical tests (with a capable scan tool)

• Monitor live data related to the TCC: TCC lockup status, duty cycle, commanded gear, engine RPM, vehicle speed, and transmission fluid temperature.
• Check whether the TCC lockup is being commanded and whether it actually locks at appropriate speeds. If commanded but never locks, suspect the solenoid or circuit.
• If your tool supports it, monitor the TCC solenoid current/solenoid duty cycle and any fault codes stored in the TCM.

Step 4: Electrical resistance and circuit checks (DC tests)

• With the ignition off, inspect and test the TCC solenoid circuit for continuity between the TCM/solenoid connector and the solenoid itself.
• Check supply voltage at the solenoid connector (kilovolt? typically 12V with ignition on) and ground integrity.
• Look for shorts to ground or power, damaged insulation, or corrosion. Compare readings against the service manual specifications.

Step 5: Fluid-related considerations

• If the ATF is degraded, discolored, or has metal shavings, plan a full transmission service and consider further diagnosis of the valve body or internal wear.
• If a transmission service is performed, ensure the correct fluid spec is used and that the service includes proper fill/level after warm-up and relearn if required.

Step 6: Targeted component testing and repair options

• TCC solenoid replacement (simple solenoid fault suspected)

  • If electrical checks and live data indicate the solenoid is not actuating, replacing the TCC solenoid is a common first repair.
  • After replacement, clear codes and perform a road test to confirm lockup behavior.

• Valve body service or cleaning

  • If fluid is good but the problem persists, and live data shows abnormal TCC behavior or stuck passages, valve body cleaning or rebuild may be necessary.

• Torque converter assessment

  • If the TCC circuit and valve body appear fine but the problem continues, the torque converter itself could be the root cause.

• Transmission service or rebuild/replacement

  • If there are signs of clutch wear, internal damage, or persistent overheating, a full transmission service or more extensive repair may be required.

Step 7: Road test and recheck

• After any repair, take a controlled road test to verify that the TCC lockup engages and remains stable across appropriate speeds. Re-check for codes and monitor live data to confirm proper operation.

Step 8: Documentation and reset

• Clear the codes after repair and monitor for reoccurrence. If the codes return, re-evaluate the diagnosis or consider more extensive transmission service.

RELATED CODES

• P0741 Torque Converter Clutch Circuit Performance or Stuck Slip

  • Often appears with P0740 as part of the TCC fault family. Check both the electrical circuit and the mechanical condition of the torque converter.

• P0742 Torque Converter Clutch Circuit Stuck Off (less common depending on model/year)

  • Indicates potential loss of TCC engagement.

• P0700 Generic Transmission Control System Malfunction

  • A general code that may accompany P0740 in some cases when the transmission control system detects an issue.

• Note: Exact related codes can vary by year, software, and configuration. Use the scan tool to identify all codes and address them in context.

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices vary by region, shop, and vehicle condition. The ranges below are general estimates for Toyota Tacoma (2016-2023) with typical labor rates.

• Quick/low-cost fixes

  • Transmission fluid change (ATF WS or specified fluid, plus filter if applicable): Parts $20–$60; Labor $100–$250; Total $120–$310.
  • TCC solenoid replacement (solenoid only): Parts $30–$120; Labor 1–2 hours; Total $200–$600.
  • Fluid flush with temperature/pressure appropriate equipment: Parts $0–$60; Labor $150–$250; Total $150–$310.

• Moderate repairs

  • Valve body service (cleaning or rebuild with warranted parts): Parts $50–$400; Labor 3–6 hours; Total $700–$1,800.
  • Transmission fluid/filter service with potential pan work: Parts $50–$120; Labor 2–4 hours; Total $250–$900.

• More extensive repairs

  • Torque converter replacement (if determined necessary): Parts $150–$500; Labor 3–6 hours; Total $700–$2,500.
  • Valve body replacement or major repair: Parts $200–$800; Labor 4–8 hours; Total $900–$3,000.

• Transmission rebuild/replacement options

  • Remanufactured/rebuilt transmission (installed): Parts $1,500–$3,500 (core, unit, etc.); Labor 8–12 hours; Total $3,000–$6,000.
  • Used/remanufactured replacement transmission: Parts $2,000–$4,500 (varies by source); Labor 6–12 hours; Total $3,500–$7,500.
  • New/GM-equivalent price ranges for Toyota-approved reman units can exceed these ranges in some regions.

• Warranty considerations

  • Many shops offer 12–36 month warranties on transmission work. Warranties vary by shop and the exact repair performed.

• Important note

  • The actual repair cost depends on the underlying cause. If the issue is resolved with a TCC solenoid replacement, you may stay on the lower end of the range. If the fault is due to valve body wear or torque converter failure, costs will be higher.

DIY vs PROFESSIONAL

• DIY-friendly tasks (potentially within reach for a skilled enthusiast)

  • Checking and replacing the TCC solenoid
  • Replacing ATF and changing a filter where applicable
  • Basic electrical checks (continuity tests, voltage checks) with a suitable multimeter and service manual
  • Resetting adaptive/transmission learn routines in some vehicles after a component change

• Tasks better left to a professional

  • Inspecting or rebuilding the valve body (requires specialty tools and precise procedures)
  • Replacing or rebuilding the torque converter
  • Internal transmission pressure testing or a full teardown
  • Diagnosing PCM/TCM software calibration or specifications
  • Any repair that involves removing the transmission or significant disassembly

• Practical tips

  • Start with the least invasive repair (solenoid or fluid service) if the fault seems electrical or fluid-related.
  • If you’re not equipped to perform high-level electrical tests or transmission disassembly, seek a qualified shop early to avoid unnecessary parts replacement.

PREVENTION

• Regular transmission service

  • Use the manufacturer-specified ATF type and follow the recommended service interval (or use a severe-service interval if you drive in extreme conditions). Avoid mixing fluids.

• Maintain cooling and temperature

  • Ensure the transmission cooler lines and radiator cooling for the transmission are clean and functioning. Overheating accelerates wear on clutches and the torque converter.

• Address leaks promptly

  • Any ATF leaks should be repaired quickly to avoid fluid loss and contamination.

• Drive smart

  • Avoid aggressive towing beyond the Tacoma’s towing specifications, fast starts with heavy loads, and excessive idling. Allow the transmission to warm up before towing or heavy use.

• Software updates

  • If your dealership has issued an TCM/PCM software update addressing TCC behavior, consider having it applied.

• Regular inspections

  • Periodic visual inspection of harnesses around the valve body area, pan, and connections can catch problems before they turn into a code.

Final notes and data transparency

• Data limitation

  • The provided NHTSA data shows no recalls and no owner complaints for P0740 on the 2016-2023 Toyota Tacoma in the dataset. This means the guide cannot rely on NHTSA complaint trends for this specific model/year. Actual field experience may differ, and service bulletins (TSBs) or manufacturer updates not captured in this dataset could exist.

• Practical approach

  • Use this guide as a structured diagnostic framework focusing on P0740. Always verify with a hands-on inspection, and consider the underlying transmission condition before choosing a repair path. If in doubt, consult a qualified transmission technician who has access to Toyota service information and up-to-date diagnostic tools.

If you’d like, I can tailor the diagnostic steps to your exact Tacoma trim (e.g., 2WD vs 4x4, with or without tow package) or provide a condensed repair cost estimate based on your region.