P0743 on 2011-2014 Kia Forte Koup: TCC Solenoid Circuit Fault Guide

What's Unique About the 2011-2014 Kia FORTE KOUP

For this generation of Kia Forte Koup with the 6-speed automatic transmission (A6MF1), Kia has issued a Technical Service Bulletin (TSB) that directly addresses P0743, among other codes. The TSB, #TSBTRA051R1, explicitly advises technicians to replace the individual solenoids rather than the entire transaxle, which is a common misdiagnosis. This indicates that solenoid failure is a recognized, widespread issue on this platform and its platform-mates (like the Hyundai Elantra and Kia Optima), and the fix is more affordable than a full transmission replacement.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: The 2011-2014 range covers the end of the first generation (2010-2013) and the start of the second generation (2014-2016) of the Forte Koup. Both generations used a 6-speed automatic transmission (model A6MF1), and the known solenoid issues and the related TSB TSBTRA051R1 apply to vehicles in this entire year range equipped with this transmission.

Symptoms You May Notice

• Check Engine Light is on
• Transmission fails to shift into the highest gear
• Higher than normal engine RPM at highway speeds
• Reduced fuel economy
• Transmission may get stuck in one gear (limp mode)
• Harsh or erratic shifting
• Engine may stall when coming to a stop
• Shuddering or vibration when stopping or at low speeds

Most Likely Causes

1. Failed Torque Converter Clutch (TCC) Solenoid 🔴 High Probability → Shop Automatic Transmission Torque Converter This is a known issue acknowledged by Kia via Technical Service Bulletin TSBTRA051R1, which specifically lists P0743 and recommends solenoid replacement. These solenoids are a high-failure item across many Hyundai/Kia models with the A6MF1 transmission.
   How to confirm: A technician can test the solenoid's internal resistance with a multimeter after accessing the valve body. For the A6MF1, the TCC solenoid is a Variable Force Solenoid (VFS) and should have a resistance of approximately 5.1-5.3 ohms. It can also be tested by applying a controlled current source, but resistance is the primary check.
   Typical fix: Replace the faulty TCC solenoid. The solenoids are located on the transmission valve body, accessible after removing the transmission pan.
   Est. part cost: $60-$120
2. Damaged Internal Transmission Wiring Harness 🟡 Medium Probability → Shop Transmission Assembly The wiring harness inside the transmission is subjected to constant heat and immersion in fluid, which can cause it to become brittle and fail over time, leading to an open or short in the TCC solenoid circuit. This is also a very common failure point on these transmissions, sometimes causing multiple solenoid codes at once.
   How to confirm: Visually inspect the wiring harness for signs of damage, brittleness, or corrosion after removing the transmission pan. Check for continuity between the main transmission connector and the TCC solenoid connector. A video from a technician working on a 2014 Sorento with the same issue showed a corroded pin on the main external connector was the root cause.
   Typical fix: Replace the internal transmission wiring harness. The typical OEM part number for this harness is 46307-3B650.
   Est. part cost: $70-$150
3. Low or Dirty Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly While not a direct cause of an electrical code, extremely low or contaminated fluid can cause solenoids to operate erratically or overheat, potentially leading to electrical failure. Many owners are not aware that this 'sealed' transmission requires fluid changes.
   How to confirm: Check the transmission fluid level and condition. On these sealed transmissions, this must be done by a technician via the fill and level check plugs with the fluid at a specific temperature (typically 122-140°F). The fluid should be bright red and not smell burnt.
   Typical fix: Perform a transmission fluid drain and fill using fluid that meets Kia's SP-IV specification.
   Est. part cost: $80-$160
4. Faulty Powertrain/Transmission Control Module (PCM/TCM) ⚪ Low Probability → Shop Transmission Assembly While possible, module failure is the least likely cause. All other possibilities should be exhausted first. TSB TSBTRA051R1 lists PCM replacement as the final step after verifying the solenoid and harness are good.
   How to confirm: This is a process of elimination. If the solenoid, wiring, and fluid are all confirmed to be good, the TCM becomes the primary suspect. A technician can use advanced scan tools to monitor the TCM's commands to the solenoid.
   Typical fix: Replace and reprogram the Powertrain or Transmission Control Module. This can be costly, with parts alone potentially exceeding $1,500.
   Est. part cost: $500-$1600

Rare But Worth Checking

• Corroded External Harness Connector:

Diagnosis Steps

1. Scan the vehicle for all stored trouble codes. Note any other transmission-related codes.
2. Check the transmission fluid level and condition. This requires the vehicle to be level and at operating temperature (122-140°F) and is best done by a professional on these sealed units.
3. Inspect the main transmission wiring harness connector for damage, corrosion, or loose pins.
4. If the external wiring is okay, the next step is to drop the transmission pan to access the internal components.
5. Visually inspect the internal wiring harness for any signs of damage.
6. Locate the TCC solenoid. Using a multimeter, test the resistance of the solenoid. Compare the reading to the manufacturer's specification. For the A6MF1 VFS solenoids, the resistance should be approximately 5.1 to 5.3 ohms at 68°F.
7. If the solenoid resistance is out of spec, it is faulty and needs to be replaced.
8. If the solenoid tests good, check for continuity and shorts in the internal and external wiring harness between the TCM and the solenoid connector.
9. If all wiring and the solenoid test good, the issue may be a faulty Transmission Control Module (TCM), though this is rare.

Parts You'll Likely Need

• Automatic Transmission Control Solenoid (TCC) (OEM #46313-3B600) — This is the most common failure part for a P0743 code on this vehicle, as confirmed by Kia's own Technical Service Bulletin. This part number is for the VFS solenoid used for multiple functions, including TCC.
  Trusted brands: Kia (OEM), Rostra
  OEM price range: $75-$115
  Aftermarket price range: $50-$80
• Automatic Transmission Internal Wire Harness (OEM #46307-3B650) — The second most likely culprit. Often replaced as a preventative measure when replacing the solenoids due to its high failure rate from heat and fluid exposure.
  Trusted brands: Kia (OEM)
  OEM price range: $100-$180
  Aftermarket price range: $60-$120
• Transmission Pan Gasket — The gasket must be replaced anytime the transmission pan is removed to prevent leaks.
  Trusted brands: Fel-Pro, Mahle
  OEM price range: $20-$40
  Aftermarket price range: $15-$25
• Kia SP-IV Automatic Transmission Fluid — The transmission fluid must be replaced after dropping the pan. Using the correct OEM-spec fluid is critical for transmission health. Approximately 4-5 quarts are needed for a pan drop.
  Trusted brands: Kia (OEM), Idemitsu
  OEM price range: $18-$25 per quart
  Aftermarket price range: $12-$18 per quart

Related Codes That Often Appear With This One

• P0741 — This code indicates 'Torque Converter Clutch Circuit Performance or Stuck Off.' It often appears with P0743 because an electrical fault (P0743) can lead to a performance problem (P0741). Both are addressed by the same TSB.
• P0748, P0753, P0758, P0763, P0768, P0773 — These are all electrical fault codes for other transmission solenoids. If the internal wiring harness is failing, it can cause multiple solenoid circuit codes to appear simultaneously. All are mentioned in TSB TSBTRA051R1.

Technical Service Bulletins (TSBs) & Recalls

• TSBTRA051R1: This bulletin provides information relating to the replacement of various shift solenoids on 6-speed automatic transaxles for multiple DTCs including P0743. It explicitly states to replace the solenoids if codes are present and NOT to replace the entire transaxle.

Platform-Specific Known Issues

• A known high failure rate of the transmission solenoids in the 6-speed automatic transmission prompted Kia to issue TSB TSBTRA051R1, which covers this specific code and vehicle range.
• The internal wiring harness is also a very common point of failure, becoming brittle from heat cycles and causing intermittent open circuits.

Mechanic-Grade Diagnostic Values

• TCC (VFS) Solenoid Resistance — expected: 5.1 - 5.3 ohms. Failure: A reading significantly higher or lower than this range, or an open (infinite) or short (zero) reading.
• TCC (VFS) Solenoid Resistance (Alternate Spec) — expected: 3.5 ± 0.2 ohms at 20°C (68°F). Failure: A reading outside of this range.
• On/Off Solenoid Resistance (e.g., SSA, SSB) — expected: 10 - 11 ohms. Failure: A reading outside of this range.
• Transmission Fluid Temperature Sensor Voltage — expected: Approx. 3.2V at 104°F (40°C) or 0.29V at 302°F (150°C). Failure: Voltage readings that do not correlate with the actual fluid temperature.
• TCC Solenoid Circuit Continuity at Main Connector — expected: Continuity between pins 10 (Solenoid Power) and 2 (TCC Solenoid).. Failure: No continuity (open circuit) indicates a break in the wiring.

Scan Tool Commands That Help

• Kia GDS (or compatible advanced scanner): Actuation Test for TCC Solenoid — To command the TCC solenoid on and off while monitoring circuit voltage or listening for a physical 'click' to determine if the solenoid is responding to TCM commands. This helps isolate a faulty solenoid from a wiring or TCM issue.
• Kia GDS (or compatible advanced scanner): Resetting Auto T/A Values (Adaptive Learn Reset) — This function should be performed after replacing solenoids or the valve body to clear the transmission's learned shift patterns and allow it to adapt to the new components, ensuring smooth shifting.

Wiring & Ground Locations

• Main Transmission Connector — Located on the top of the transaxle case, typically found under the battery and battery tray.. This is the primary interface between the external vehicle harness and the internal transmission harness. Corrosion or damage to pins here (specifically pins for solenoid power and the TCC solenoid) can cause a P0743 code, mimicking an internal failure.
• Transmission Ground Strap (2011-2013) — A dedicated ground cable that connects the transmission case to the vehicle's chassis.. A poor ground connection can cause erratic voltage in electrical circuits, potentially leading to false solenoid fault codes. Ensuring this strap is clean and tight is a crucial electrical check. The OEM part number is 918601M140.
• Transmission Ground Strap (2014) — A dedicated ground cable connecting the transmission case to the chassis for the second-generation Forte Koup.. A poor ground connection can cause electrical issues for the transmission. The OEM part number for the 2014+ auto trans model is 91860-A7220.
• TCM TCC Solenoid Control Pin — Pin 25 on the Transmission Control Module (TCM) connector is often designated for TCC Solenoid Valve Control.. This is the specific pin where a technician can back-probe to test the voltage signal being sent from the TCM to the solenoid, confirming if the module is commanding the solenoid correctly.

Real Owner Repair Stories

• Go-Parts.com summary of a repair video (2014 Kia Sorento (with same A6MF transmission family)) — P0743 code present.
  ❌ Tried (didn't work) Initial diagnosis pointed towards a common internal solenoid or harness failure.
  ✅ What actually fixed it The actual cause was corrosion found on pins 5 and 10 of the main external transmission connector. The fix was to thoroughly clean the connector pins with electrical contact cleaner, which restored continuity and resolved the code without replacing any internal parts.

When the Usual Fixes Don't Work

• While the TSB and high failure rates point directly to the TCC solenoid, it should not be replaced without proper diagnosis. A documented repair on a similar Kia with the same transmission family found the root cause to be corrosion on the main external transmission connector. A full diagnostic procedure, starting with external checks of wiring and connectors, should always be performed before removing the transmission pan. This can prevent the unnecessary cost and labor of replacing a perfectly good solenoid.

OEM Part Supersession History

• 46307-3B610, 46307-3B620 → 46307-3B650 — Updated design or manufacturer change for the internal transmission wiring harness.
  Heads up: The older part numbers have been replaced by 46307-3B650. Using the newest part number is recommended for reliability.
• 46313-23000 → 46313-23010 (Verify by VIN) — Part for a different transmission family.
  Heads up: Part number 46313-23000 is for older 4/5-speed transmissions and is physically different. It will not work in the 6-speed A6MF1 transmission. Ensure the correct part is ordered for the 6-speed.

Model Year Variations Within This Range

• 2011-2013 vs 2014: The OEM part number for the transmission ground strap cable is different. For 2011-2013 models, it is 918601M140. For the 2014 model with an automatic transmission, it is 91860-A7220.