Input/Turbine Speed Sensor Circuit
Diagnostic trouble code P0715 indicates a malfunction in the input/turbine speed sensor circuit. The powertrain control module (PCM) or transmission control module (TCM) sets this code when it fails to receive a valid, consistent signal from the input speed sensor, which is necessary to determine the transmission's input RPM.
While the vehicle can usually still be driven, it may enter a fail-safe or 'limp' mode, restricting gears and causing harsh shifts. It should be diagnosed and repaired soon to prevent potential internal transmission damage and restore normal drivability.
Common symptoms
- Illuminated Check Engine Light
- Harsh or erratic transmission shifting
- Transmission stuck in limp mode (restricted to one gear)
- Transmission slipping or delayed engagement
- Speedometer functioning erratically or not at all (on some vehicles)
Likely causes
- Defective input/turbine speed sensor
- Damaged, corroded, or loose wiring and connectors in the sensor circuit
- Contaminated transmission fluid containing excessive metal debris
- Faulty shift solenoids or internal transmission mechanical failure
- Defective Powertrain Control Module (PCM) or Transmission Control Module (TCM) (rare)
What to check before replacing parts
Check the transmission fluid level and condition.
Look for: Fluid that is excessively dirty, burnt, or contains metal shavings can interfere with the magnetic sensor's ability to read the reluctor wheel.
Visually inspect the wiring harness and connector for the input speed sensor.
Look for: Look for frayed wires, melted insulation, corrosion in the connector pins, or a loose connection that could cause an open or short circuit.
Test the input speed sensor resistance using a digital multimeter.
Look for: Compare the measured resistance across the sensor terminals to the manufacturer's specifications. An open circuit (infinite resistance) or a short indicates a failed sensor.
Check the sensor circuit for proper voltage and ground from the PCM/TCM.
Look for: With the key on, engine off, verify that the reference voltage and ground are present at the sensor connector according to the wiring diagram.
Monitor the input speed sensor signal using a scan tool with live data capabilities.
Look for: While driving or with the engine running in gear, look for a steady RPM reading that matches engine speed (when the torque converter is locked). An erratic, dropping, or zero reading confirms a signal issue.
This page explains the generic P0715 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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