OBD-II Code P0718: Input/Turbine Speed Sensor 'A' Circuit Intermittent

What Does P0718 Mean?

Code P0718 means your Powertrain Control Module (PCM) or Transmission Control Module (TCM) is receiving an erratic, unstable signal from the transmission's Input Speed Sensor 'A'. This sensor measures how fast the transmission's input shaft spins. The computer requires this exact data to dictate gear shifts, control hydraulic line pressure, and manage the torque converter lock-up clutch.

Technical definition: The SAE/OBD-II definition is "Input/Turbine Speed Sensor 'A' Circuit Intermittent". The PCM/TCM detects the voltage signal from the input speed sensor dropping in and out, deviating from its expected stable pattern.

Can I Drive With P0718?

Yes, But With Caution. You can drive short distances to a repair shop, but doing so risks severe damage. The transmission often shifts harshly, locks into one gear ('limp mode'), or stalls the engine, making driving unsafe. Continuing to drive causes accelerated internal transmission wear due to high fluid temperatures and erratic pressures, turning a simple sensor fix into a 🎬 Watch: How to repair a turbine input sensor on 4L60E transmissions. $3,000+ transmission replacement.

Common Causes

• Faulty Input/Turbine Speed Sensor (Very Common) — The sensor fails internally from heat cycles, or its magnetic tip collects metallic particles from normal transmission wear, disrupting the signal.
• Damaged Wiring or Connectors (Common) — The wiring harness suffers damage from engine heat, chafing, or moisture. Connectors loosen or corrode, causing the exact intermittent connection that defines this code.
• Low or Contaminated Transmission Fluid (Common) — Dirty or degraded fluid accelerates internal wear, generating metallic debris that blinds the sensor's magnetic tip. Fluid also leaks past a faulty O-ring into the connector, shorting the circuit.
• Faulty Powertrain/Transmission Control Module (PCM/TCM) (Less Common) — The computer module reading the signal fails. Internal circuit problems, like cracked solder joints, prevent it from interpreting sensor data.
• TCM Software or Calibration Glitch (Uncommon) — The TCM's firmware contains a bug causing it to falsely set P0718. A manufacturer software update (reflash) resolves this.
• Internal Transmission Mechanical Issues (Rare) — Severe internal problems, like a damaged reluctor wheel or worn clutches, cause incorrect speed readings and generate excessive debris.
• Interference from Other Faulty Components (Rare) — A failing Crankshaft Position Sensor or a bad alternator creating electrical 'noise' (AC ripple) tricks the TCM into registering an input speed sensor fault.

Symptoms

• Erratic, Harsh, or Delayed Shifting — The transmission slams into gear, hesitates, shifts at incorrect times, or slips between gears.
• Transmission is Stuck in 'Limp Mode' — The transmission defaults to a single gear (usually 2nd or 3rd) to prevent internal damage, severely limiting speed and acceleration.
• Check Engine Light is On — The computer illuminates the Malfunction Indicator Lamp (MIL). Some vehicles also flash a dedicated transmission warning light.
• Engine Stalling — When stopping, the confused TCM fails to unlock the torque converter, stalling the engine like a manual transmission left in gear.
• Erratic or Inoperative Speedometer — If the vehicle uses input speed data for the speedometer, the needle jumps erratically or drops to zero.
• Decreased Fuel Economy — Inefficient shifting forces the engine outside its optimal RPM range, increasing fuel consumption.

Diagnostic Flowchart

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

Common Fixes & Costs

• Replacing the Input/Turbine Speed Sensor — Parts: $25-$110, Labor: $120-$300, ~1.5 hr book time (DIY)
• Repairing Damaged Wiring or Connectors — Parts: $10-$50, Labor: $100-$250, ~1.5 hr book time (Intermediate)
• Transmission Fluid and Filter Service — Parts: $50-$150, Labor: $100-$250, ~1 hr book time (Intermediate)
• TCM Software Update — Parts: $0, Labor: $100-$200, ~0.5 hr book time (Professional)
• Replacing the Transmission Control Module (TCM) — Parts: $800-$1500, Labor: $200-$400, ~2 hr book time (Professional)

DIY vs Professional

• Replacing the Input/Turbine Speed Sensor — Beginner:
• Repairing Damaged Wiring or Connectors — Beginner:
• Transmission Fluid and Filter Service — Beginner:
• TCM Software Update — Beginner:
• Replacing the Transmission Control Module (TCM) — Beginner:

Used vs. New Parts: Buying Guide

When a used part is worth it: For a simple electronic part like an input speed sensor, buying used rarely makes sense. The low cost of a new part combined with the labor cost for installation means the risk of a premature failure on a used sensor is not worth the minimal savings.

Donor-vehicle mileage cap: roughly under 40000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Source from a low-mileage vehicle totaled due to collision, not scrapped for powertrain issues.
• Ensure the part number matches exactly.
• Visually inspect the connector pins for any corrosion or damage.

Decision logic:

• If The new part costs less than $150 → Always buy new. The warranty and peace of mind are worth more than the small potential savings.
• If The vehicle is very old (>20 years) and the part is no longer available new → A used part is your only option. Test it for correct resistance before installation.
• If The part is electronic with no moving parts (like a sensor) → Strongly favor new, as heat cycles and age degrade electronics internally in ways that are not visible.

Warranty tradeoff: Used parts typically offer a 30-90 day warranty, which does not cover labor costs. New aftermarket parts come with a 1-year to limited lifetime warranty.

Worst-case if a used part fails: 200-400, representing the cost of repeat labor to replace a faulty used sensor, plus the cost of another part.

What Happens If You Wait — Timeline

1. 0-1 month: Check Engine Light is on. Occasional, barely noticeable hesitation or slightly firm shift. No other major symptoms. (MPG impact: 0-2%% · Added cost: $0-20 in wasted fuel.)
2. 1-4 months: Shifting becomes noticeably erratic, with intermittent harsh engagements or delays. Fuel economy drops. The transmission occasionally enters 'limp mode' but resets after restarting the car. (MPG impact: 5-10%% · Added cost: $50-150 in wasted fuel and minor accelerated clutch wear.)
3. 4-8 months: Harsh shifting is common. The vehicle gets stuck in 'limp mode' frequently, becoming unreliable. Erratic line pressure causes significant wear on clutch packs and internal seals. (MPG impact: 10-15%% · Added cost: $800-$1,500 as internal damage (worn clutches, seals) becomes likely.)
4. 8+ months: Catastrophic internal failure is imminent. Constant harsh shifting and high fluid temperatures destroy clutches, damage the valve body, or harm the torque converter. (MPG impact: 15-25%% · Added cost: $2,500-$6,000+ as the transmission requires a complete rebuild or replacement.)

Cost of Not Fixing It

• 0-1 month: Noticeable harsh shifting, potential stalling, and a 5-10% drop in fuel economy. Driving is annoying but major damage is not yet likely. (Added cost: 25-50)
• 1-6 months: Accelerated wear on transmission clutches and internal seals due to erratic hydraulic pressures and harsh engagement. Increased risk of being stranded in 'limp mode'. (Added cost: Potential for hundreds in related component wear.)
• 6+ months: Catastrophic internal transmission failure. The added stress destroys clutches, the torque converter, or the valve body, requiring a complete transmission rebuild. (Added cost: 2500-6000+)

Diagnosis Steps

1. Check for Technical Service Bulletins (TSBs)
   Check for manufacturer TSBs related to P0718 for your specific vehicle. A known software glitch or common wiring issue saves hours of diagnostic time.
   Tools: Online Repair Database or Dealer Access (Beginner)
2. Read Codes and Analyze Freeze Frame Data
   Use an OBD-II scanner to confirm P0718 and check for related codes (e.g., P0717, P0720). Analyze freeze-frame data to see vehicle speed and engine RPM when the fault occurred, providing critical clues about the intermittent fault.
   Tools: OBD-II Scanner (Beginner)
3. Check Transmission Fluid
   Check the transmission fluid level and condition. Dark, burnt-smelling, or glittery fluid indicates internal wear generating the debris that causes sensor issues.
   Tools: Rag, Dipstick (if equipped) (Beginner)
4. [PRO TIP] Perform a 'Wiggle Test'
   With the scanner graphing Input Speed Sensor data, start the engine and let it idle. Manually wiggle the wiring harness at the sensor connector and along its path. If the RPM reading drops to zero or spikes, you found the intermittent open or short in the wiring.
   Tools: Advanced OBD-II Scanner with Live Data Graphing (Advanced)
5. Visually Inspect Wiring and Connectors
   Inspect the wiring harness from the input speed sensor to the TCM. Look for melting, chafing against the engine, corrosion in the connector, or fluid contamination.
   Tools: Flashlight, Inspection Mirror (Intermediate)
6. Clean and Inspect the Sensor
   Remove the input speed sensor. Wipe the metallic 'fuzz' off its magnetic tip and inspect the housing for cracks. Look through the sensor hole to check the reluctor wheel for broken teeth.
   Tools: Wrenches/Sockets, Rag (Intermediate)
7. Test Sensor Circuit Voltage and Resistance
   Disconnect the sensor and check for the correct reference voltage (typically 5V) and ground with the key on. Next, measure the internal resistance across the sensor's pins (often 650-1,300 Ohms). An infinite (open) or near-zero (short) reading confirms a failed sensor.
   Tools: Digital Multimeter (DVOM), Vehicle-Specific Service Manual (Advanced)
8. [ADVANCED] Live Data PID Analysis
   Monitor live data PIDs for 'Input Shaft Speed' and 'Output Shaft Speed' while driving at a steady speed. If the Input Shaft Speed drops to zero or freezes while the Output Shaft Speed remains steady, the fault is isolated to the input sensor's circuit.
   Tools: Advanced OBD-II Scanner with Live Data (Advanced)
9. [PRO TIP] Analyze the Waveform with an Oscilloscope
   Back-probe the sensor's signal wire with an oscilloscope. A healthy sensor produces a clean digital square wave or AC sine wave that increases in frequency with RPM. Any 'noise' or dropouts in the waveform confirms an intermittent fault.
   Tools: Oscilloscope (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 180-200°F (The fault typically occurs when the vehicle is fully warmed up.)
• Engine RPM: 1500-2500 RPM (Often triggered during steady-state cruising, not necessarily during hard acceleration.)
• Engine Load: 30-60% (Happens under moderate engine load, consistent with city or highway driving.)
• Vehicle Speed: 35-55 mph (The intermittent signal dropout is often caught at constant highway or arterial road speeds.)

Related Codes

• P0717 — This code means 'Input/Turbine Speed Sensor 'A' Circuit No Signal'. P0718 is for an intermittent signal, while P0717 means the signal is completely gone. A fault that starts as P0718 eventually becomes a hard failure and sets P0717.
• P0716 — This code means 'Input/Turbine Speed Sensor 'A' Circuit Range/Performance'. This sets when the sensor produces a signal, but it is irrational or doesn't logically match engine RPM. P0718 is about the signal cutting out entirely.
• P0720 — This is the 'Output Speed Sensor Circuit' code. The computer compares input speed to output speed to verify gear ratios. Graphing both sensor signals on a scanner isolates whether the input or output sensor is dropping out.
• P0700 — This is a generic 'Transmission Control System Malfunction' code. It is an informational code set by the PCM to tell you the TCM stored a fault. You always see P0700 alongside a specific transmission code like P0718.

Climate & Environmental Factors

• Cold Weather: Extreme cold thickens transmission fluid, causing delayed shifts. It also causes wiring insulation and connector seals to contract and harden, worsening existing intermittent electrical connections.
• High Humidity/Moisture: Moisture accelerates corrosion on connector pins and grounds. This corrosion creates unwanted resistance, disrupting the sensitive voltage signal from the speed sensor.

How to Talk to a Mechanic About This Code

Say this: "I have a P0718 code for an intermittent input speed sensor. I'd like to schedule a diagnosis. Please make sure the technician tests the sensor circuit, including a 'wiggle test' of the harness, before recommending a sensor replacement."

This signals that you understand the common failure points for an intermittent code are often wiring-related. It directs the mechanic to perform a thorough electrical diagnosis instead of just replacing the most likely part.

Avoid saying:

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

Questions to ask before authorizing the repair:

• Did you find the problem with the sensor itself or in the wiring/connector?
• Were you able to replicate the signal drop-out while monitoring live data?
• Did you check for reference voltage and ground at the sensor connector?
• Are there any Technical Service Bulletins (TSBs) for this code on my car?
• What is the warranty on this specific repair, including parts and labor?

Where to Take It: Dealer vs Independent vs Chain

• Dealer:
  Best for: Vehicles under warranty (especially Ford PowerShift or Subaru CVT), Known manufacturer-specific issues requiring software updates, Complex repairs where the sensor is internal to the transmission (e.g., Mercedes conductor plate)
  Downsides: Higher labor rates, May replace a larger assembly (like a valve body) when an independent shop might attempt a smaller repair (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit for most cases. An experienced independent technician effectively diagnoses the sensor, wiring, and fluid at a significantly lower cost than a dealer.
  Best for: Out-of-warranty vehicles where cost is a major factor, Diagnosing and repairing common external sensors and wiring issues
  Downsides: Quality and expertise vary widely; look for shops specializing in transmissions or with ASE-certified technicians. (Typical cost: +0% vs. baseline)
• Chain Shop: Use with caution. Acceptable if you are certain the external sensor is faulty and just need it replaced. AVOID for initial diagnosis of an intermittent problem like P0718.
  Best for: Simple, clear-cut part replacements if you have already diagnosed the problem yourself.
  Downsides: Technician skill varies greatly; lacks the diagnostic experience for an intermittent electrical fault, leading to part-swapping. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 40-50% of the car's private-party value, it is time to seriously consider selling or trading it in.

• Car worth $8000, fix is $400: Fix it. This is a minor repair well below the threshold.
• Car worth $4000, fix is $2200: Walk away. The repair is over 50% of the car's value and indicates a major transmission issue.
• Car worth $2500, fix is $1500: Walk away. The repair cost is 60% of the vehicle's value. It is not a sound financial decision.

What Scan Tool You Need for This Code

Minimum: A scanner that displays and graphs live data, specifically the 'Input Shaft Speed' PID.

A basic code reader only tells you the P0718 code exists. It cannot show you the live RPM signal from the sensor, which is essential for seeing intermittent dropouts and performing a 'wiggle test'.

Budget: BlueDriver Pro / Ancel BD310 (~$90) — Connects to your smartphone and provides live data graphing for the input speed sensor. This is sufficient for a skilled DIYer to watch the signal and perform a wiggle test.

Mid-range: Foxwell NT510 Elite / Innova 5610 (~$150) — These handheld units offer dedicated full-system diagnostics, including transmission data. They provide faster and more stable live data streaming to catch quick, intermittent signal drops.

Professional: Autel MaxiCOM MK808 / Launch CRP919E (~$500) — Provides professional-level, fast live data graphing and recording. Their speed and ability to access manufacturer-specific transmission data are invaluable for complex cases.

Rent vs buy: If this is a one-time diagnosis, many auto parts stores offer a tool loaner program. Buy a scanner only if you plan to perform your own diagnostics regularly.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to erase the P0718 code.
2. Perform a complete OBD-II drive cycle to allow readiness monitors to run.
3. Rescan the vehicle to confirm no codes have returned.

Drive cycle (~30 minutes): Start the engine from cold and let it idle for 2-3 minutes. Drive in stop-and-go city traffic for 10-15 minutes. Drive at a steady highway speed (55-60 mph) for 10-15 minutes. Allow the vehicle to cool down completely (8 hours) and repeat if monitors are not set.

Readiness monitors affected: Comprehensive Component Monitor, Misfire Monitor, Catalyst Monitor, Evaporative System Monitor

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Clearing the code does not fix the underlying mechanical or electrical problem; the code returns if the repair was not successful.
• Taking the car for an emissions test immediately after clearing the code results in a 'Not Ready' failure because the drive cycle has not been completed.

Will This Fail Emissions / State Inspection?

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

• California: An illuminated Check Engine Light is an automatic failure. After repair, a full drive cycle must be completed to set readiness monitors before a retest is possible.
• New York: The NYS DMV inspection includes an OBD-II scan. A P0718 code causes an automatic failure of the emissions portion of the test.
• Texas: In counties requiring emissions testing, an active P0718 code results in an inspection failure.

Most Commonly Affected Vehicles

• Ford Focus, Fiesta (2012-2018) — Vehicles with the DSP6 PowerShift transmission are notorious for TCM failures and sensor issues. For 2012-2016 models, TSB 16-0129 addresses many of these concerns, which manifest as P0718. Often the TCM itself is the root cause.
• Chevrolet Cruze, Sonic, Aveo (2011-2016) — These models with 6T30/6T40/6T45 transmissions suffer from failed internal wiring harnesses or a faulty sensor. Technicians inspect the internal harness for brittleness whenever the pan is off.
• Subaru Outback, Forester, Impreza, Crosstrek (with CVT) (2010-2019) — On many Subaru CVT models, the input and output speed sensors are integrated into the valve body assembly. A P0718 code points to a failing valve body, a highly expensive repair. Subaru extended the CVT warranty on many of these models to 10 years/100,000 miles.
• Honda Accord, Civic, Fit (2012-2017) — These models are known for intermittent failures of the mainshaft (input) speed sensor. Honda issued TSB 17-043 for some models to address harsh shifting and torque converter judder related to fluid degradation.
• Jeep Grand Cherokee (WJ) (1999-2004) — Input and output speed sensor failures are a very common fault on this generation. On the 4.7L V8 with the 45RFE/545RFE transmission, the two sensors look identical and are often replaced as a pair.
• Hyundai/Kia Various (Elantra, Sonata, Forte, Optima) (2010-2018) — Many models from this era are prone to P0718 due to a faulty sensor or issues with the internal transmission wiring harness. On some models, the sensors are internal and require removing the valve body.
• Chrysler/Dodge Various with 42RLE/6F24 Transmissions (2000-2012) — Vehicles from this era experience issues with sensor packs. On the 42RLE, the input and output sensors are part of a single assembly. On the 6F24, the sensors are internal and require valve body removal.
• Nissan Altima, Maxima, Rogue (with CVT) (2007-2015) — Nissan CVTs are highly sensitive to fluid condition. A P0718 code is triggered by fluid breakdown, but is also commonly associated with a failing valve body assembly containing the speed sensors.

Manufacturer-Specific Notes

• Honda/Acura: On models like the Accord and TSX, an intermittent P0718 is triggered by deteriorated transmission fluid causing torque converter judder, which the system misinterprets as a sensor failure. A fluid flush and software update (TSB 17-043) resolves this.
• Chrysler/Jeep/Dodge: A failing Crankshaft Position Sensor (CKP) sends erratic signals that the TCM misinterprets, setting a P0718 code even if the transmission sensor is perfectly fine.
• Ford: For vehicles with the DPS6 PowerShift transmission, P0718 is a primary symptom of a failing Transmission Control Module (TCM). Ford initiated Customer Satisfaction Program 14M02, extending the TCM warranty to 10 years or 150,000 miles.
• Mercedes-Benz: On models with the 722.9 7G-Tronic transmission, the speed sensors are integrated into the conductor plate. A P0718 code requires replacing the entire conductor plate and specific dealer programming.
• Subaru: Subaru extended the CVT warranty for many 2010-2019 models to 10 years/100,000 miles. This covers failures of the valve body, which contains the speed sensors (reference service bulletin 16-115-18).

Real Owner Stories

2013 Ford Focus at 85,000 miles

Check engine light came on, transmission shuddered and shifted very harshly, sometimes losing power completely.

Outcome: The TCM was replaced under Ford's Customer Satisfaction Program 14M02, extending the warranty to 10 years or 150,000 miles. The repair was free, and shifting returned to normal.

Lesson: If you own a 2011-2016 Fiesta or 2012-2016 Focus with shifting problems, check if your vehicle is covered by Ford's extended TCM warranty (14M02) before paying for repairs.

2012 Honda Fit at 118,000 miles

Transmission started to shudder, and the check engine light came on, revealing code P0718.

Outcome: Forum members advised doing multiple drain-and-fills with the correct Honda ATF-DW1 fluid. Honda transmissions are highly sensitive to fluid type.

Lesson: Never underestimate the importance of manufacturer-specified transmission fluid. Using a 'universal' fluid causes shifting problems that mimic sensor failures.

2008 Mercedes GL550 with Limp Mode

The vehicle went into limp mode, and the scanner showed code P0718, pointing to a defective turbine speed sensor on the 722.9 transmission's conductor plate.

Outcome: On these Mercedes models, a fluid change is a common first attempt before undertaking the expensive replacement of the conductor plate.

Lesson: When a sensor is internal and hard to access, a fluid and filter service is a cost-effective first step. Old fluid causes issues that a simple service resolves.

Honda Accord with P0717 & P0718

After driving half a mile, the check engine light came on, the 'D' light blinked, and the transmission would not shift into higher gears. Codes P0717 and P0718 were present.

Outcome: A mechanic advised the issue was in the wiring. Testing revealed a lack of 5V reference on the Yellow/Blue wire, pointing to a wiring or PCM ground issue, not the sensor.

Lesson: Replacing the part is not always the fix. An intermittent code combined with a 'no signal' code points to a wiring issue. Test the circuit's voltage and ground before buying parts.

How to Prevent This Code From Triggering

• Change transmission fluid and filter at recommended intervals (Every 30,000 to 60,000 miles for most vehicles.) — Removes metallic debris that sticks to the magnetic tip of the speed sensor, disrupting its signal. It prevents fluid breakdown and wear that create debris.
• Use only the manufacturer-specified transmission fluid (OEM) (Every fluid change.) — Modern transmissions are highly sensitive to fluid viscosity. Using the wrong fluid causes shuddering or slipping that the TCM misinterprets as a sensor fault.
• Inspect and secure wiring harnesses near heat sources (During every oil change.) — The sensor's wiring harness becomes brittle from constant exposure to engine heat. Ensuring harnesses are secured prevents chafing and melting that cause intermittent shorts.
• Install protective heat shielding on vulnerable wiring (Once, as a proactive upgrade.) — Adding a high-temperature heat shield sleeve to wiring near the exhaust manifold provides a robust barrier against heat degradation, extending the life of the wiring insulation.
• Avoid aggressive driving and excessive towing (Daily habit.) — Hard acceleration increases transmission temperature and internal wear, leading to faster fluid breakdown and the creation of metallic debris.

Frequently Asked Questions

What does the Input/Turbine Speed Sensor do?

It is a magnetic or Hall-effect sensor that measures the rotational speed of the transmission's input shaft. The car's computer uses this data to control gear shifts, manage the torque converter clutch, and monitor for internal transmission slippage.

What is a common misdiagnosis for P0718?

A common mistake is replacing the input speed sensor without inspecting the wiring harness. Because the code means an intermittent fault, a chafed wire or corroded connector perfectly mimics a faulty sensor. Performing a live-data 'wiggle test' prevents this costly error.

Can a bad battery cause a P0718 code?

Yes. A failing battery or bad alternator causes low or unstable system voltage. This makes electronic modules behave erratically and sets false diagnostic codes like P0718.

Can I fix a P0718 code myself?

If the cause is a dirty or faulty sensor externally mounted on the transmission, it is a manageable DIY repair. If the sensor is internal to the transmission (requiring pan/valve body removal) or the problem is with the wiring or computer, take the vehicle to a transmission specialist.

Will clearing the P0718 code fix the problem?

No. Clearing the code only turns off the check engine light temporarily. The fault still exists, and the code returns as soon as the computer detects the signal drop-out again.

Where is the Input Speed Sensor located?

It is typically mounted on the outside of the transmission housing near the bell housing. However, on certain Hyundai, Kia, and Chrysler models, the sensor is located inside the transmission and requires removing the oil pan to access.

What is the difference between an input speed sensor and an output speed sensor?

The Input Speed Sensor measures the speed of the shaft coming from the engine, while the Output Speed Sensor measures the speed of the shaft going out to the wheels. The computer compares these two speeds to determine the gear ratio and detect slippage.

Key Takeaways

• Code P0718 indicates the transmission's input speed sensor is sending an intermittent, on-and-off signal to the powertrain control module.
• Expect harsh shifting, engine stalling, and the transmission locking into 'limp mode' (usually 2nd or 3rd gear) to prevent internal damage.
• The top 3 causes are a failed sensor ($150-$400 repair), chafed wiring harnesses, or dirty transmission fluid coating the sensor's magnetic tip.
• Perform a live-data 'wiggle test' on the sensor's wiring harness before buying parts; intermittent codes are frequently caused by a $20 wiring short rather than a bad sensor.
• Driving with an active P0718 code for more than a few days risks catastrophic clutch and valve body failure, turning a minor fix into a $3,000+ transmission rebuild.