P0715 on 2015-2016 Ford Flex: Input/Turbine Speed Sensor 'A' Circuit Failure Causes and Fixes

What's Unique About the 2015-2016 Ford Flex

The Ford Flex from this era uses the 6F50/6F55 automatic transmission, shared with platform mates like the Ford Explorer, Edge, and Lincoln MKT. While generally reliable, issues with transmission speed sensors are a known issue across various Ford models using this family of transmissions. For the 2015-2016 models, the cause is most often an isolated failure of the sensor itself or its wiring, rather than a widespread design flaw covered by a specific recall for this component.

Symptoms You May Notice

• Harsh, erratic, or delayed gear shifts
• Vehicle entering 'limp mode' or 'fail-safe' mode with limited speed
• Check Engine Light is on
• Flashing Overdrive light or transmission warning message on the dash
• Decreased fuel economy
• Inability to shift into higher gears
• Engine stalling when coming to a stop
• Erratic or non-functional speedometer (less common, usually associated with the output speed sensor, but can occur)

Most Likely Causes

1. Defective Input/Turbine Speed Sensor (TSS) 🔴 High Probability → Shop Automatic Transmission Input Shaft Speed Sensor The sensor is an electronic component that operates in a high-temperature environment. Over time, heat cycles and vibration can cause the internal circuitry to fail.
   How to confirm: A diagnostic scan tool can monitor the live data from the TSS. If the reading is erratic, zero, or doesn't change with engine RPM while in gear, the sensor is likely faulty. A technician can also test the sensor's resistance with a multimeter after removing it from the transmission.
   Typical fix: Replace the Turbine Speed Sensor. This involves draining the transmission fluid and removing the side cover of the transmission to access the sensor.
   Est. part cost: $50-$200
2. Damaged Wiring or Connectors 🟡 Medium Probability The wiring harness leading to the transmission is exposed to the elements, road debris, and heat from the engine/exhaust. This can lead to chafed or broken wires, or corrosion in the connector pins.
   How to confirm: Visually inspect the wiring harness going to the transmission for any signs of chafing, breaks, or corrosion at the connectors. Perform a continuity test on the wires from the sensor connector to the TCM connector.
   Typical fix: Repair the damaged section of the wiring harness or replace the connector. Ensure the repaired section is properly insulated and secured away from heat sources.
   Est. part cost: $20-$100
3. Low or Dirty Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly While not a direct cause of a circuit malfunction code, very low or contaminated fluid can cause erratic transmission behavior and overheating, which can contribute to sensor failure. Metal shavings from internal wear suspended in the fluid can also stick to the magnetic tip of the sensor, disrupting its signal.
   How to confirm: Check the transmission fluid level and condition using the dipstick. The fluid should be at the correct level and reddish-pink, not brown, black, or smelling burnt.
   Typical fix: Perform a transmission fluid drain and fill, or a full fluid exchange if the fluid is heavily contaminated. This is often done as part of the sensor replacement.
   Est. part cost: $100-$250 (for fluid and filter)

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM): → Shop Transmission Assembly This is very rare. The PCM/TCM should only be considered after all other possibilities, including the sensor, wiring, and even internal mechanical components, have been thoroughly tested and ruled out.
• Internal Transmission Mechanical Failure: → Shop Transmission Assembly A severe internal issue, like a failing torque converter or a damaged reluctor wheel (the toothed ring the sensor reads), can cause erratic speed readings. This would typically be accompanied by other symptoms like loud grinding noises, severe slipping, or significant metal debris in the transmission pan.

Diagnosis Steps

1. Connect a diagnostic scan tool and confirm that P0715 is the primary code. Note any other transmission-related codes.
2. Use the scan tool to monitor the live data stream for the Input/Turbine Speed Sensor (TSS).
3. Observe the TSS reading while the vehicle is in gear and the engine RPM is raised. The TSS RPM should increase smoothly with the engine RPM.
4. If the TSS reading is erratic, intermittent, or stuck at zero, the problem is likely the sensor or its circuit.
5. Perform a thorough visual inspection of the transmission wiring harness and connectors for any visible damage, corrosion, or loose connections.
6. If wiring appears okay, access the sensor. This requires partial disassembly as it's located inside the transmission side cover.
7. Once the sensor is removed, inspect its magnetic tip for any metal shavings or debris. An accumulation of metal indicates potential internal transmission wear.
8. Check the sensor's internal resistance with a multimeter and compare it to the manufacturer's specifications. Also, test for proper voltage and ground at the sensor's connector.
9. If the sensor and wiring test good, the issue may be with the reluctor wheel inside the transmission or, in rare cases, the TCM itself.

Parts You'll Likely Need

• Automatic Transmission Input/Turbine Speed Sensor (OEM #8A8Z-7M101-A (Note: This part may be superseded by AA5Z-7M101-B)) — This sensor is the most common failure point for the P0715 code.
  Trusted brands: Motorcraft, Dorman, Standard Motor Products (SMP)
  OEM price range: $150-$200
  Aftermarket price range: $50-$120

Related Codes That Often Appear With This One

• P0717 — P0717 indicates 'Input/Turbine Speed Sensor A Circuit No Signal', which is a more specific version of the P0715 fault. They often appear together if the sensor has completely failed or the wiring is severed.
• P0720 — This code relates to the Output Speed Sensor (OSS). If both input and output speed sensor codes appear, it could point to a larger wiring harness issue affecting both sensors, a bad ground, or a problem with the TCM.
• P0722 — Similar to P0717, this code indicates 'Output Speed Sensor Circuit No Signal'. Seeing P0715 and P0722 together strongly suggests a shared wiring or power issue.

Platform-Specific Known Issues

• Accessing the Sensor is Labor Intensive: On the Ford Flex with the 6F50/6F55 transmission, the input and output speed sensors are located behind the transmission side cover. This requires removing the driver's side wheel, axle shaft, and various suspension components to gain access, making it a more involved repair than on transmissions where the sensors are externally mounted.
🎬 Watch: Ford Flex turbine speed sensor replacement walkthrough
• Forum User Experience: A user on the Reddit r/FordFlex subreddit described classic P0715 symptoms including abnormal shifting. Another user correctly identified the code as relating to the Input/Turbine Speed Sensor circuit and listed the common causes, corroborating that a faulty sensor, wiring, or internal transmission issue are the primary culprits.

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• Internal Water Pump Failure (3.5L V6) 🔴 High — Can occur anytime after 60,000 miles, becoming more common at higher mileage. Failure can be catastrophic if coolant leaks into the engine oil. (Ref: While no specific recall for the 2015-16 Flex, the design is a known industry-wide issue and subject of class-action lawsuits. A coolant leak from a 'weep hole' on the passenger side of the engine block, near the alternator, is the primary warning sign.)
• Power Transfer Unit (PTU) Failure (AWD Models) 🔴 High — Common at mileages over 80,000, especially if the fluid has never been changed. The 'lifetime' fluid gets cooked by the nearby exhaust, leading to breakdown and gear failure. (Ref: TSB 19-2017 addresses fluid leaks from the PTU seals. Symptoms include a burning gear oil/propane smell, whining or grinding noises, and fluid leaks on the passenger side.)
• MyFord Touch / SYNC 2 Infotainment System Failure 🟠 Medium — Common across the entire lifespan of the vehicle. Issues include frozen/unresponsive touchscreens, system reboots, and loss of features like Bluetooth or navigation. (Ref: Ford issued a warranty extension (12M02) for the APIM module, extending coverage to 5 years from the original purchase date. The root cause is often a failed touchscreen digitizer or a faulty APIM module.)
• Fractured Rear Toe Links 🔴 High — Affects 2013-2018 models. Can lead to a sudden loss of steering control. (Ref: Ford issued safety recall 19S17 to replace the rear toe links on affected vehicles free of charge.)
• Faulty Fuel Pump Control Module 🔴 High — Affects 2013-2015 models. Can cause the engine to stall without warning or fail to start. (Ref: Ford issued safety recall 16S31 for this issue.)

Real Owner Stories

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

Related OBD-II Codes

• P0720 — This code refers to the Output Speed Sensor (OSS); while P0715 is for the input sensor, both are located behind the transmission side cover on the Flex and often fail due to similar heat and vibration cycles.
• P0700 — A general transmission control system malfunction code that often accompanies specific sensor codes like P0715 to trigger the Check Engine Light.
• P0219 — Engine overspeed condition; can be triggered if the TSS provides erratic or zero readings, causing the TCM to lose track of input speeds and fail to shift correctly.
• P0731 — Incorrect gear ratio codes can occur alongside P0715 when the TCM cannot reconcile the engine RPM with the input speed sensor data during gear engagement.

Frequently Asked Questions