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DTC codes / P27xx · Transmission / P2765

P2765Input/Turbine Speed Sensor 'B' Circuit

P2765 indicates that the transmission control module has detected an abnormal signal on the 'B' input/turbine speed sensor circuit, which monitors the rotational speed of the transmission input shaft. The computer compares this signal to other speed sensors and sets the code when the expected voltage or signal pattern is missing, erratic, or out of range.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light, often with no other noticeable symptoms
  • Harsh or delayed shifting as the transmission loses the ability to accurately judge input speed
  • The transmission may enter limp mode, sticking in a single gear or refusing to downshift
  • Erratic speedometer readings or a jumpy tachometer if the sensor shares data with the instrument cluster
  • Poor fuel economy and increased engine RPM during cruising due to incorrect shift scheduling
  • In some cases, the vehicle may stall or hesitate when coming to a stop because the torque converter clutch strategy is affected

Common causes, most likely first

  1. A faulty input/turbine speed sensor 'B' that has failed internally or is contaminated with metallic debris
  2. Damaged, chafed, or corroded wiring in the sensor circuit, especially near the transmission connector or along the harness
  3. A loose or corroded electrical connector at the sensor or at the transmission control module
  4. Metal debris buildup on the sensor tip, often from a failing transmission component, which disrupts the magnetic pickup
  5. An internally failing transmission control module that cannot process the sensor signal correctly
  6. A mechanical issue inside the transmission, such as a damaged reluctor wheel or input shaft, that prevents the sensor from reading properly
  7. Low or contaminated transmission fluid that causes poor sensor performance or intermittent signal loss

How to diagnose and fix it

  1. Use an OBD-II scan tool to retrieve all stored and pending codes, then record freeze-frame data to see the conditions when P2765 set
  2. Visually inspect the input speed sensor, its connector, and the wiring harness for damage, corrosion, or loose pins, repairing as needed
  3. Check the sensor resistance and signal output with a multimeter or oscilloscope according to the manufacturer's specifications
  4. Remove the sensor and inspect the tip for metallic debris or physical damage, cleaning or replacing it if necessary
  5. Check transmission fluid level and condition, topping off or changing the fluid if it is low or contaminated
  6. Perform a voltage drop test on the sensor circuit and verify the reference voltage and ground at the sensor connector
  7. If all external checks pass, test the transmission control module and internal wiring, consulting a professional transmission specialist if internal damage is suspected

What the input speed sensor code hides

  • A common misdiagnosis is replacing the input speed sensor when the real problem is a chafed wire hidden inside the harness loom, so always perform a wiggle test on the wiring while watching live data.
  • Metallic debris on the sensor tip often points to a failing transmission component rather than the sensor itself, so cleaning the sensor without investigating the source of the debris will lead to a repeat failure.
  • Some vehicles use the input speed sensor signal for the speedometer and cruise control, so a fault can cause apparent instrument cluster issues that are actually transmission-related.
  • A low or contaminated transmission fluid level can cause intermittent input speed sensor codes because the sensor may not get proper lubrication or cooling, so always check fluid condition before condemning electrical parts.
  • The code can set intermittently due to temperature-related connector expansion, so a sensor that tests good when cold may still be faulty when the transmission reaches operating temperature.

Can I keep driving with P2765?

You can usually drive the vehicle with P2765 set, but avoid aggressive acceleration and towing until the fault is repaired because the transmission may shift erratically or enter limp mode. If the vehicle feels unsafe or refuses to shift, stop driving and have it towed to a repair shop.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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