OBD-II Code P1710: Transmission Component Malfunction

What Does P1710 Mean?

P1710 is a manufacturer-specific code, meaning its definition changes by vehicle make. For Subaru, it points to a failed Turbine Speed Sensor 2. For Nissan and Infiniti, it indicates a Transmission Fluid Temperature Sensor fault. For Honda, it flags a faulty gear selection switch. In all cases, the transmission control module (TCM) detects improper voltage from a critical sensor, severely affecting drivability.

Technical definition: As a P1xxx code, P1710 is not standardized by SAE/ISO. Common definitions include: 'Torque Converter Turbine 2 Speed Signal Circuit Malfunction' (Subaru), 'Transmission Fluid Temperature Sensor Circuit Malfunction' (Nissan/Infiniti), and 'First Hold Switch Circuit Fault' (Honda/Acura).

Can I Drive With P1710?

Yes, But With Caution. You can physically drive, but you will experience harsh, violent shifting or the transmission will enter 'limp mode,' limiting gears. Continued driving is highly discouraged. Forceful shifting puts extreme stress on internal gears, clutches, and mounts. Driving more than 50 miles turns a simple sensor fix into a catastrophic transmission failure, adding $1,800-$3,400+ for a rebuild or replacement.

Common Causes

• Faulty Turbine Speed or Fluid Temperature Sensor (Very Common) — The turbine speed sensor (Subaru) or fluid temperature sensor (Nissan) fails internally due to heat and age, sending incorrect signals to the computer.
• Internal Valve Body Harness Failure (Common) — On Subarus with the 5EAT transmission, the internal wiring harness insulation becomes brittle and breaks, causing an open or short circuit even if the sensor itself is functional.
• Damaged or Corroded External Wiring/Connectors (Common) — The external wiring harness leading to the transmission frays, shorts, or corrodes from road debris and moisture, disrupting the signal to the TCM.
• Contaminated or Low Transmission Fluid (Less Common) — Dirty, sludgy, or low fluid causes erratic sensor readings. Metal shavings accumulate on magnetic speed sensors, disrupting their function.
• Failing Transmission Control Module (TCM) or Software Glitch (Rare) — The computer controlling the transmission fails or requires a software update, causing it to misinterpret sensor signals and trigger the P1710 code.

Symptoms

• Harsh or Erratic Shifting — A sudden, violent bang or lurch when the transmission shifts gears, feeling like being rear-ended. Prevalent between 2nd and 3rd gear on affected Subarus.
• Check Engine Light and/or AT Temp Light On — The check engine light illuminates. On Subarus, the 'AT OIL TEMP' light flashes to indicate a transmission-specific fault.
• Vehicle Enters 'Limp Mode' — The transmission gets stuck in a single gear (often 3rd) to prevent further damage, severely limiting vehicle speed.
• Hesitation or Lag on Acceleration — The vehicle feels sluggish when accelerating from a stop as the TCM struggles with incorrect sensor data.
• Reduced Fuel Economy — Inefficient shifting and improper torque converter lock-up decrease gas mileage.

Diagnostic Flowchart

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

Common Fixes & Costs

• Replace Turbine Speed Sensor / Transmission Fluid Temperature Sensor — Parts: $20-$120, Labor: $200-$500, ~2.5 hr book time (Intermediate)
  : OEM
  : OEM
• Replace Transmission Valve Body — Parts: $400-$2,800, Labor: $300-$1,000, ~3.5 hr book time (Professional)
  : OEM
  : OEM
• Repair or Replace Damaged Wiring — Parts: $10-$50, Labor: $100-$400, ~2 hr book time (Intermediate)
• Transmission Fluid and Filter Change — Parts: $50-$150, Labor: $100-$250, ~1 hr book time (DIY)
• Reprogram or Replace Transmission Control Module (TCM) — Parts: $50-$1,200, Labor: $100-$300, ~1.5 hr book time (Professional)
  : OEM

Used vs. New Parts: Buying Guide

When a used part is worth it: For a Subaru P1710, buying a used valve body is not recommended because the speed sensor is a known failure point; buy a new aftermarket sensor instead. For a Nissan, a professionally remanufactured and programmed valve body is a cost-effective alternative to a new OEM unit.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• For remanufactured valve bodies, verify the seller offers a warranty and programs the unit to your VIN.
• Ensure the part number exactly matches or is a confirmed supersession for your specific model and year.

Decision logic:

• If Fix is replacing the sensor on a Subaru valve body → Always buy a new aftermarket sensor; a used one has no remaining life expectancy.
• If Fix is replacing the entire valve body assembly (Nissan or Subaru) → A warrantied, remanufactured unit from a reputable supplier is the best balance of cost and reliability.

Warranty tradeoff: New aftermarket sensors typically have a 1-year warranty. Remanufactured valve bodies often come with a 1-year to limited lifetime warranty. Used parts from salvage yards have 30-90 day warranties at best.

Worst-case if a used part fails: 800-1500 if a used/reman valve body fails, including repeat labor and a replacement unit.

What Happens If You Wait — Timeline

1. 0-1 month: Intermittent fault. The Check Engine Light / AT Temp light illuminates but shifting feels normal most of the time. Harsh shifts occur only when hot or under heavy load. (MPG impact: 0-5%% · Added cost: $0)
2. 1-3 months: Consistent fault. Harsh, banging shifts become frequent. The transmission enters 'limp mode' more often. Stress on transmission and engine mounts increases. (MPG impact: 5-10%% · Added cost: $50-200 in wasted fuel and initial mount stress.)
3. 3-6 months: Mechanical damage begins. Constant violent shifting causes premature wear on friction surfaces of internal clutch packs and cracks gear teeth. Fluid overheats and forms sludge. (MPG impact: 10-15%% · Added cost: $500-$1,500 (Repair now requires a partial rebuild to replace worn clutches).)
4. 6+ months: Catastrophic failure. A major internal hard part, like a clutch drum or gear set, fails completely. The vehicle loses the ability to move. (MPG impact: 15-25%% · Added cost: $2,500-$5,000+ (Cost of a rebuilt or new transmission).)

Cost of Not Fixing It

• 0-1 Month (0-500 miles): Severe, harsh shifting continues. Fuel economy drops by 5-10%. Stress on transmission mounts begins. (Added cost: 0)
• 1-6 Months (500-3,000 miles): Violent shifting causes premature wear on internal clutch packs and gear sets. Fluid overheats, accelerating internal damage. (Added cost: 500-1500)
• 6+ Months (3,000+ miles): Catastrophic internal transmission failure occurs. The repair escalates to a full transmission rebuild or replacement. (Added cost: 2500-5000+)

Diagnosis Steps

1. Scan for Codes
   Confirm the P1710 code. Look for P0700 (general transmission fault), which often appears alongside P1710 to request the check engine light.
   Tools: OBD-II Scanner (Beginner)
2. Monitor Live Data (Speed/Temp)
   Use an advanced scan tool. For Subaru, monitor 'Turbine Speed Sensor 2' (should increase smoothly with RPM). For Nissan, monitor 'Transmission Fluid Temperature' (should rise steadily to 158-212°F). Stuck or erratic values confirm a sensor/circuit failure.
   Tools: Advanced OBD-II Scanner with manufacturer-specific PIDs (Intermediate)
3. Check Transmission Fluid
   Verify fluid level and condition. Fluid should be bright red. Dark, burnt-smelling, or low fluid contributes to the problem.
   Tools: Rag, Dipstick (if equipped) (Beginner)
4. Inspect External Wiring and Connectors
   Visually inspect the external wiring harness going to the transmission for chafing, melting, or corrosion on the connector pins.
   Tools: Flashlight (Beginner)
5. Pro-Level: Test Sensor Resistance
   Disconnect the sensor and measure resistance. A Subaru turbine sensor reads 1.0–1.3 kΩ. A Nissan temp sensor reads ~4kΩ at 68°F. Infinity (open) or zero (short) confirms a failed sensor.
   Tools: Multimeter, Vehicle-specific repair manual (Advanced)
6. Pro-Level: Check for Reference Voltage
   Back-probe the TCM connector to verify circuit integrity. For Subaru, check voltage between specified pins for Turbine Speed Sensor 2. You should see a reference voltage (VCC) of 4-6 V with ignition on.
   Tools: Multimeter, Back-probe kit, Vehicle-specific wiring diagram (Advanced)
7. Inspect Internal Components
   Drain fluid and remove the transmission oil pan to inspect the sensor and internal wiring harness on the valve body.
   Tools: Socket set, Drain pan, Gasket scraper, Torque wrench (Advanced)
8. Pro-Level: Use an Oscilloscope
   For intermittent issues, connect an oscilloscope to the sensor's signal wire. A healthy turbine speed sensor produces a clean square or sine wave. A missing or distorted waveform points definitively to a sensor/circuit problem.
   Tools: Oscilloscope, Back-probe kit (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Vehicle Speed: 35-55 mph (During or just after a 2-3 gear shift at steady cruise or light acceleration.)
• Engine RPM: 1500-2500 RPM (The moment the TCM commands a gear change and the expected change in turbine speed does not occur.)
• Transmission Fluid Temp: 160-220°F (71-104°C) (After at least 15-20 minutes of driving, when the fluid is hot and thin.)

Related Codes

• P0700 — A general transmission fault code indicating the TCM has stored a specific code (like P1710) and requested the check engine light. You will almost always see P0700 alongside P1710.
• P0715 — Refers to an 'Input/Turbine Speed Sensor 'A' Circuit Malfunction.' If your P1710 relates to a speed sensor (Subaru), you may see this generic code as well.
• P0710 — The generic OBD-II code for 'Transmission Fluid Temperature Sensor 'A' Circuit Malfunction'. On Nissan vehicles, P1710 is the manufacturer-specific equivalent.
• P0720 — Indicates a fault with the 'Output Speed Sensor Circuit.' If you have both P1710 and P0720, it points to a wiring issue common to both sensors or a significant internal problem.

Climate & Environmental Factors

• Extreme Heat: High ambient temperatures increase transmission operating temperature, accelerating fluid breakdown and stressing electronic components like sensors.
• High Humidity / Moisture: Moisture accelerates corrosion on external connectors and wiring harnesses, increasing electrical resistance and disrupting the sensor signal.
• Extreme Cold: Thicker transmission fluid in cold weather causes slower shifts initially, adding strain that exposes pre-existing intermittent sensor issues.

How to Talk to a Mechanic About This Code

Say this: "I have a P1710 code on my [Make, Model] and am experiencing [symptom, e.g., 'harsh 2-3 shifts']. My research indicates this is commonly a failure of the [Turbine Speed Sensor 2 for Subaru / Transmission Fluid Temperature Sensor for Nissan]. I want to book a diagnostic appointment to confirm if the sensor or its wiring circuit is the fault before replacing the entire valve body."

This signals you are an informed customer. It focuses the technician on the most likely and affordable fix first, preventing them from defaulting to an expensive component replacement. For a Subaru, it specifically opens the door to the cheaper sensor-only repair.

Avoid saying:

• 'Just fix whatever's wrong'
• 'My check engine light is on, can you look at it?'
• 'Whatever you recommend is fine'

Questions to ask before authorizing the repair:

• For a Subaru: Did you test the resistance of the Turbine Speed Sensor 2, and what was the reading? Do you solder in replacement sensors, or do you only replace the full valve body?
• For a Nissan: Did you inspect the transmission fluid for coolant contamination? Can you show me the live data from the Transmission Fluid Temperature sensor?
• What is the warranty on the parts and labor for this specific repair?
• Will I get a detailed invoice showing the specific part numbers and labor breakdown?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Use for warranty claims or complex Nissan TCM replacements. Avoid for an out-of-warranty Subaru to prevent overcharging.
  Best for: Vehicles still under a powertrain warranty, Complex repairs on Nissan/Infiniti models requiring a new programmed valve body/TCM assembly
  Downsides: Significantly higher labor rates., For Subarus, dealers almost always quote a full valve body replacement ($1800+) instead of the cheaper sensor-only repair ($500-$800). (Typical cost: +50% vs. baseline)
• Independent Shop: The best choice for this code. An experienced independent transmission shop is far more likely to perform the sensor-level repair, saving you thousands.
  Best for: Out-of-warranty vehicles, especially Subarus with the 5EAT transmission., Owners seeking the cost-effective sensor-only solder repair.
  Downsides: Quality varies; ensure they have specific experience with internal transmission work. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID for P1710. This job requires diagnostic and mechanical skill not typically found at a chain shop.
  Best for: Simple maintenance like oil changes or brake jobs.
  Downsides: Technician skill is highly variable and rarely specialized enough for internal transmission work., High risk of misdiagnosis or recommending an unnecessary transmission replacement. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 40-50% of the car's current private-party value, sell the car as-is or for scrap.

• Car worth $5000, fix is $3300: Walk away. A dealer quote for a valve body on an older Subaru often exceeds the threshold. Get a second opinion from an independent shop before deciding.
• Car worth $12000, fix is $800: Fix it. An independent shop repair for the sensor is well below the threshold and restores the vehicle's value.
• Car worth $4000, fix is $4500: Walk away. If a Nissan has coolant contamination requiring a full transmission rebuild, the cost exceeds the vehicle's value.

What Scan Tool You Need for This Code

Minimum: A scanner that reads manufacturer-specific live data for the transmission module.

A basic $20 code reader only shows the P1710 code. It cannot display essential live data, such as 'Turbine Speed Sensor 2' (Subaru) or 'Transmission Fluid Temperature' (Nissan), required to confirm the sensor is failing.

Budget: Autel AP200 or similar Bluetooth dongle (~$60) — Connects to a smartphone app and accesses manufacturer-specific systems like the TCM to read live data, sufficient to diagnose a failing speed or temperature sensor.

Mid-range: Foxwell NT510 Elite (~$180) — A powerful handheld tool offering OE-level diagnostics. It graphs live data, accesses the transmission module, and performs service adaptations needed after repair.

Professional: Autel MaxiCOM MK808 / MK906BT (~$500-1200) — Professional-grade tools with full bidirectional control, extensive live data graphing, and all OEM-level functions, including programming or relearn procedures after a valve body replacement.

Rent vs buy: Auto parts stores offer loan-a-tool programs, but their scanners are often too basic to read manufacturer-specific live data for P1710. Buying a budget or midrange scanner is a worthwhile investment.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear the P1710 and related codes.
2. For Subaru, perform a transmission relearn procedure using an advanced scan tool.
3. For Nissan, perform a transmission adaptation/relearn if the valve body/TCM was replaced.
4. Perform a complete drive cycle to allow the TCM to verify the repair.

Drive cycle (~20 minutes): Cold start and idle for 2-3 minutes. Accelerate to 45-55 mph and hold for 5-7 minutes. Perform 5-10 slow stops from 25 mph to 0 mph. Drive in stop-and-go traffic for 5-7 minutes. Let the vehicle cool down completely.

Readiness monitors affected: Comprehensive Component Monitor, Transmission

Before emissions retest: drive at least 50 miles to fully set monitors.

Watch out for:

• Disconnecting the battery will not clear the code from the TCM's permanent memory or perform the relearn procedure.
• Failing to perform the manufacturer-specific transmission relearn procedure results in continued poor shifting.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An illuminated Check Engine Light results in an automatic failure. All OBD-II readiness monitors must be 'Ready' to pass.
• New York: The NYS DMV emissions inspection includes an OBD-II scan. A P1710 code causes an automatic failure.
• Texas: In counties requiring emissions testing, an active P1710 code and illuminated Check Engine Light is an automatic failure.

Most Commonly Affected Vehicles

• Subaru Legacy, Outback (2008-2014) — Extremely common on models with the 5EAT automatic transmission. The failure is almost always the Turbine Speed Sensor 2. Aftermarket sensors are available (e.g., part numbers 31705AA620, 31705AA662).
• Subaru Tribeca (2008-2014) — Equipped with the 5EAT transmission, making it prone to the same P1710 turbine speed sensor failure.
• Subaru Exiga (2008-2014) — Shares transmission technology with the Legacy and Outback, leading to the same common P1710 code.
• Nissan Pathfinder, Titan, Frontier (2005-2012) — P1710 typically points to a failure in the A/T Fluid Temperature Sensor circuit. The sensor is integrated into the valve body/TCM assembly, which must be replaced as a unit.
• Acura TL, MDX (2003-2006) — On some Acuras, P1710 indicates a fault with the 'First Hold Switch Circuit' or its associated wiring, requiring a different diagnostic path than Subaru or Nissan.

Manufacturer-Specific Notes

• Subaru: P1710 almost always means the Turbine Speed Sensor 2 failed. Subaru does not sell this sensor separately and recommends replacing the entire valve body for over $1,800. However, aftermarket sensors can be soldered into the valve body harness for a fraction of the cost.
• Nissan / Infiniti: P1710 indicates a 'Transmission Fluid Temperature Sensor Circuit' malfunction. The sensor is integrated into the control valve with the TCM and is not sold separately, requiring the entire assembly to be replaced.
• Acura / Honda: Unlike other makes, P1710 on Honda/Acura vehicles indicates a 'First Hold Switch Circuit Fault'. Diagnosis must focus on the specific gear position switch and its circuit, not speed or temperature sensors.

Real Owner Stories

2008 Subaru Legacy GT with 5EAT

Owner experienced intermittent but violent hard shifts, especially under acceleration. The AT Temp, ABS, and traction control lights flashed. The car occasionally went into limp mode. A P1710 code was present.

What they tried:

1. Initial research pointed to the Turbine Speed Sensor 2.
2. The official Subaru fix was a new valve body quoted at $3,300.

Outcome: The owner opted for a DIY fix by removing the valve body and soldering in a new aftermarket Hall effect sensor (Part: SENSPD500). The total cost was a fraction of the dealer quote, resolving all shifting issues.

Lesson: For Subaru 5EAT transmissions, P1710 is almost always the Turbine Speed Sensor 2. Do not replace the entire valve body; solder in a new aftermarket sensor.

2005 Nissan Pathfinder with RE5R05A

Vehicle experienced transmission failure due to engine coolant leaking into the transmission fluid from a failed internal radiator cooler, destroying the TCM and solenoids.

What they tried:

1. A shop diagnosed coolant contamination causing short circuits in the TCM.

Outcome: The fix required a full transmission rebuild. The technician noted the solenoids were visibly damaged and required replacement. The radiator was bypassed to prevent repeat failure.

Lesson: On Nissans with the RE5R05A transmission, P1710 can be a symptom of coolant contamination. Bypassing the radiator's internal transmission cooler with an external one early can save the transmission.

2007 Acura TL with P1710

Owner experienced transmission issues and pulled a P1710 code. Unlike Subaru or Nissan, this code pointed to a 'First Hold Switch Circuit Fault'.

What they tried:

1. Researched the code and found it was unrelated to common speed/temp sensor failures.

Outcome: The diagnostic path required testing the specific gear position switch and its wiring for continuity.

Lesson: P1710 is manufacturer-specific. On Honda/Acura vehicles, it relates to a gear position switch, requiring a completely different diagnostic approach.

How to Prevent This Code From Triggering

• Perform regular transmission fluid changes (Every 30,000-60,000 miles) — Clean fluid lubricates components and dissipates heat. Old fluid leads to overheating, the primary killer of transmission electronics like sensors.
• Install an external transmission cooler (especially for Nissan RE5R05A) (Once, as a preventative upgrade) — Bypassing the radiator with an external cooler completely eliminates the catastrophic failure mode of coolant leaking into the transmission fluid.
• Check transmission fluid level and condition (Monthly) — Low fluid causes overheating. Checking color and smell provides an early warning of internal issues or contamination before major failure.
• Avoid aggressive driving and improper shifting (Daily habit) — Sudden stops, hard accelerations, and shifting from drive to reverse while moving put immense stress on internal components, accelerating wear.

Frequently Asked Questions

Can I just replace the sensor on my Subaru instead of the whole valve body?

Yes. While dealerships quote $1,800+ to replace the entire valve body, independent shops and DIYers successfully fix P1710 by soldering a $50 aftermarket sensor onto the existing wiring harness. This targeted repair saves over $1,000.

Is fixing P1710 a DIY job?

Only for advanced DIYers. The Subaru repair requires draining fluid, dropping the transmission pan, removing the valve body, and precisely soldering a new sensor. Nissan repairs often require replacing the entire valve body and programming the new TCM with an advanced scan tool.

I replaced the sensor but the P1710 code came back. What now?

Meticulously inspect the internal wiring harness, as wires frequently break inside the insulation. Check the main transmission connector for loose pins or corrosion. If using an aftermarket Subaru sensor, verify the wire colors match the OEM schematic, as incorrect soldering causes immediate failure.

What is the most common misdiagnosis for P1710?

The most common misdiagnosis is replacing the entire transmission or valve body without testing the specific sensor circuit first. Dealerships often default to a full $1,800+ valve body replacement for Subarus when only a $50 sensor has failed. Always demand a sensor resistance test before authorizing major component replacement.

What happens if I keep driving with a P1710 code?

Continuing to drive causes severe mechanical damage. The harsh, slamming shifts put extreme stress on internal transmission clutches, gears, and engine mounts. Driving more than 50 miles can escalate a $400 sensor repair into a $3,500 transmission rebuild.

Will changing the transmission fluid fix a P1710 code?

No, fresh fluid will not fix a hard electrical fault like a dead sensor or broken wire. While changing dirty fluid is good maintenance, it cannot repair the physical circuit failure triggering the P1710 code.

Why did the 'AT OIL TEMP' light start flashing?

The transmission computer flashes this light to warn you of a critical system fault that compromises safe shifting. It indicates the computer has lost vital sensor data (like turbine speed or fluid temperature) and is operating in a fail-safe mode to prevent overheating.

Key Takeaways

• Diagnose a P1710 code by testing the Turbine Speed Sensor on Subarus or the Transmission Fluid Temperature Sensor on Nissans, as these two components account for over 80% of failures.
• Stop driving immediately if you experience violent, banging gear shifts accompanied by a flashing 'AT OIL TEMP' light, as this indicates the transmission is in a damaging fail-safe mode.
• Save up to $1,300 on Subaru P1710 repairs by soldering a $50 aftermarket speed sensor into the existing valve body harness instead of paying a dealership for a complete valve body replacement.
• Limit driving to less than 50 miles after a P1710 code appears to prevent a $400 sensor repair from escalating into a $3,500 complete transmission rebuild due to shattered internal clutches.