P0706 on 2014-2021 Mazda 6 SkyActiv-G: Transmission Range Sensor Causes and Fixes

What's Unique About the 2014-2021 Mazda 6

On the 2014-2021 Mazda 6 with the SkyActiv-Drive automatic transmission (model FW6A-EL), the transmission range sensor is not a simple, external bolt-on switch like on many older vehicles. Instead, it is located inside the transmission and integrated with the control valve body and TCM. This makes diagnosis and replacement more complex. Additionally, a separate but extremely common issue is a faulty microswitch within the shifter assembly in the center console. This switch can produce identical symptoms, such as a no-start-in-park condition, and is addressed by a specific Mazda Technical Service Bulletin (TSB). Distinguishing between the internal sensor and the shifter switch is the primary diagnostic challenge for this code on this vehicle.

Symptoms You May Notice

• Check Engine Light and/or AT (Automatic Transaxle) warning light is on
• Vehicle will not start when the shifter is in Park, but may start in Neutral.
• Ignition stays on in accessory mode after the engine is shut off and the shifter is in Park.
• Incorrect gear position displayed on the instrument cluster, or the indicator light (e.g., 'D' or 'P') may turn off.
• Harsh or delayed gear engagement.
• Transmission gets stuck in one gear (limp mode) or shifts erratically.
• Reverse lights do not work.
• Cruise control is inoperative.

Most Likely Causes

1. Faulty Shifter Assembly Switch Unit 🔴 High Probability Mazda issued a Technical Service Bulletin (TSB 05-004/16, which supersedes 05-007/15) for a known issue with a worn microswitch inside the shifter assembly for 2014-2016 models. The material of the switch was improved to prevent wear. This issue is widely reported in owner forums and can affect later model years as well.
   How to confirm: A primary symptom is the ignition not turning off completely (staying in accessory mode) when the shifter is in Park. A technician can test the switch's output signals as the shifter is moved. A DIY-friendly test involves pushing the shift lever fully to the left while in Park; if the ignition then turns off correctly, the switch is failing.
   Typical fix: Replace the switch unit inside the center console shifter assembly. The part is relatively inexpensive, but labor involves disassembling the center console. There are numerous video guides available showing this process.
   Est. part cost: $40-$80
2. Internal Transmission Range Sensor Failure 🟡 Medium Probability The range sensor is integrated into the transmission's internal control valve body/TCM assembly, where it is exposed to heat and transmission fluid, leading to eventual electronic failure. On SkyActiv transmissions, this component is not serviced separately; it requires replacement of the entire valve body or TCM assembly.
   How to confirm: This requires a diagnostic scan tool that can read live transmission data. A technician will monitor the sensor's output voltage/signal for each gear position. A signal that is erratic, absent, or incorrect, while the shifter switch is confirmed to be working, points to an internal failure.
   Typical fix: The transmission valve body must be removed to replace the faulty sensor or the entire valve body/TCM assembly. This is a complex job that requires draining the transmission fluid and should be performed by a qualified transmission specialist.
   Est. part cost: $300-$800 for the valve body assembly
3. Damaged Wiring or Corroded Connector ⚪ Low Probability While the sensor is internal, the wiring harness leading to the main transmission connector can still be damaged by road debris, heat, or moisture. This is less common than component failure but should not be overlooked.
   How to confirm: Visually inspect the main transmission wiring harness and connector for any signs of damage, corrosion, or loose pins. Perform a continuity and resistance test on the relevant wires between the TCM and the transmission connector.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the corroded connector.
   Est. part cost: $10-$50

Rare But Worth Checking

• Faulty Transmission Control Module (TCM): While the range sensor is often part of the TCM/valve body assembly, the logic portion of the module can fail independently, misinterpreting a valid signal. This is uncommon and should be considered only after other causes are ruled out.
• Low or Contaminated Transmission Fluid: Dirty or low transmission fluid can cause a variety of shifting problems and, in some cases, may contribute to erratic sensor readings or valve body issues that could trigger a P0706 code.

Diagnosis Steps

1. Scan the TCM for any other transmission-related codes to get a full picture of the fault.
2. Verify the symptoms. Confirm if the car starts in Neutral but not in Park, and check if the ignition stays on after shutdown.
3. Perform the shifter switch test: With the engine off and shifter in Park, press the start/stop button to turn the ignition off. If it stays in accessory mode, push the shift lever to the left. If the car now turns off completely, the shifter switch unit is faulty.
4. If the shifter switch test is inconclusive, use a scan tool to monitor the live data from the transmission range sensor while moving the shifter through all gears (P, R, N, D, M). Note any positions where the reading is irrational or doesn't match the shifter position.
5. Inspect the main transmission electrical connector for corrosion, moisture, or damaged pins.
6. Following the procedure in TSB 05-004/16 (supersedes 05-007/15), access and test the shifter assembly switch unit located in the center console. This is the most common point of failure.
7. If the shifter switch is confirmed to be good but the signal from the transmission is still faulty, the problem is the internal range sensor. This requires professional service to access the transmission's valve body.

Parts You'll Likely Need

• Shifter Assembly Switch Unit (OEM #KDY0-46-040) — This switch inside the console is a known failure point documented by Mazda TSB 05-004/16 and is the most frequent cause of starting and gear selection signal issues. The replacement part is an improved design.
  Trusted brands: Mazda (OEM)
  OEM price range: $40-$80
  Aftermarket price range: $20-$40
• Transmission Valve Body / Control Module — On the SkyActiv-Drive transmission, the range sensor is integrated into the valve body assembly. If the sensor itself fails, the entire unit often needs to be serviced or replaced.
  Trusted brands: Mazda (OEM)
  OEM price range: $300-$800
  Aftermarket price range: N/A

Related Codes That Often Appear With This One

• P0705 — This code indicates a malfunction in the Transmission Range Sensor circuit, which is a closely related fault.
• P0707 — This code points to a 'Circuit Low Input' for the range sensor, which can be triggered by the same root causes as P0706.
• P0708 — This code points to a 'Circuit High Input' for the range sensor, also related to the same component failure.
• P0842, P0847, P0872, P0877, P0780, P1738 — These are other transmission-related DTCs concerning oil pressure switches and shift errors. Mazda has a TSB (05-005/16) for these codes on the Mazda 6, caused by contamination in the control valve body. Their presence alongside P0706 strongly suggests a broader internal transmission issue rather than just the shifter switch.

Technical Service Bulletins (TSBs) & Recalls

• 05-004/16 - Supersedes 05-007/15. Addresses a worn switch unit in the shifter assembly that causes the ignition to stay on in accessory mode when in Park. Applies to 2014 Mazda 6 and 2013-2014 CX-5. The fix is to replace the switch with an improved part (KDY0-46-040).
• 05-007/15 - The original TSB for the faulty shifter switch, now superseded by 05-004/16.

Platform-Specific Known Issues

• A known issue, documented in TSB 05-004/16 (superseding 05-007/15), involves the failure of a microswitch within the center console's shifter assembly. This commonly causes the ignition to remain in accessory mode after shutdown and can prevent the car from starting in Park, directly mimicking a P0706 fault.
• Forum discussions frequently highlight the 'shifter wiggle test' as a definitive home diagnostic: if pushing the shifter to the left while in Park allows the car to turn off fully, the shifter switch (KDY0-46-040) is the culprit.

Mechanic-Grade Diagnostic Values

• FW6A-EL On/Off Solenoid Resistance — expected: 11-14 ohms. Failure: A reading outside this range indicates a faulty solenoid within the valve body.
• FW6A-EL Pressure Control Solenoid Resistance — expected: 5-7 ohms. Failure: A reading outside this range indicates a faulty solenoid within the valve body.
• Generic Range Sensor Voltage (Key On, Engine Off) — expected: Approximate values: Park ≈ 0V, Reverse ≈ 5V, Neutral ≈ 2.5V, Drive ≈ 4V.. Failure: Deviations greater than ±0.5V suggest a sensor or wiring issue. Note: These are generic values, not specific to Mazda, but provide a diagnostic baseline.

Real Owner Repair Stories

• YouTube channel 'Darius Green' (2013 Mazda CX-5 with 227,000 miles (uses the same shifter switch as the Mazda 6)) — When putting the car in Park and pressing the stop button, the engine turns off but the accessories stay on. To fully turn off the car, the owner had to hold the shift lever to the left while pressing the stop button.
  ✅ What actually fixed it The problem was resolved by replacing the shifter assembly switch unit, part number KDY0-46-040, located inside the center console. The video provides a step-by-step guide for the replacement.

OEM Part Supersession History

• Unknown (original worn-out switch) → KDY0-46-040 — The original switch unit was prone to wear. The superseding part KDY0-46-040 is made of an improved material to increase wear resistance.

Model Year Variations Within This Range

• 2014-2016: These earlier model years are explicitly called out in TSB 05-004/16 for the shifter switch failure. While the issue is known to occur on later models, the TSB officially covers these years, making warranty claims or dealer awareness higher for this range.

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• Infotainment 'Ghost Touch' and CMU Failure 🟠 Medium — Very common on 2016+ models. The screen may register phantom touches or the entire unit may reboot. Mazda has a warranty extension program (CSP13) for this issue, not a formal recall. (Ref: Customer Service Program (CSP13))
• SkyActiv-G Intake Valve Carbon Buildup 🟠 Medium — A known characteristic of all Gasoline Direct Injection (GDI) engines. Buildup can occur over 80,000-100,000 miles, potentially causing misfires or reduced fuel economy. Mazda's design aims to minimize this, but it is not immune.
• Water Pump Seepage/Failure 🟡 Low — Minor coolant seepage or staining near the water pump's bleed hole is considered normal by Mazda per TSB SA-035/24. However, actual leaks or failures can occur and should be properly diagnosed to avoid unnecessary replacement. (Ref: SA-035/24)
• Cracked Cylinder Head (2.5T Engine Only) 🔴 High — Affects the turbocharged 2.5T engine, not the base SkyActiv-G. Coolant can leak from cracks near the exhaust manifold. This was the subject of a class-action lawsuit and is addressed by TSB 01-002/23a. (Ref: 01-002/23a)
• Prematurely Warped Brake Rotors 🟡 Low — A common complaint among owners is that the OEM brake rotors tend to warp easily, causing vibration during braking.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For the common shifter switch failure, a used center console shifter assembly from a low-mileage donor vehicle (ideally 2017 or newer to potentially have the updated part from the factory) can be a cost-effective option. The entire assembly is often easier to find and swap than the small internal switch.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Verify the donor vehicle's model year; newer is better.
• If possible, test the 'shifter wiggle' on the donor car before removal to see if it has the same fault.
• Inspect the shifter assembly for any signs of liquid spills or physical damage.
• Ensure all connectors and wiring pigtails are intact.

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

• Transmission Valve Body / Control Module: Due to the complexity, need for programming, and risk of contamination, this part should only be sourced new from Mazda to ensure compatibility and function.
• Shifter Assembly Switch Unit (KDY0-46-040): Since the new OEM part is an improved design and relatively inexpensive ($40-$80), buying it new is highly recommended over harvesting a used one.

Brands owners have reported issues with on this vehicle:

• Unbranded shifter switches from online marketplaces. While cheap, reviews are mixed, and failure of this part can leave you stranded or with a dead battery. Given the low cost of the OEM revised part, the risk is not worth the small savings.

Real Owner Stories

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

Related OBD-II Codes

• P0780 — A shift malfunction code that often appears alongside P0706 when the TCM receives irrational signals regarding gear position or shift timing.
• P0705 — Transmission Range Sensor Circuit malfunction; closely related to P0706 as both involve the TCM's inability to confirm the correct shifter position.

Frequently Asked Questions