Input/Turbine Speed Sensor "A" Circuit Malfunction
The transmission input speed (turbine) sensor signal is missing or implausible. Without this signal, the TCM cannot detect torque converter slip or calculate gear ratio in real time, and shifts become harsh.
Affected components
- Transmission input speed sensor
- Transmission input speed sensor wiring
Common causes
- High likelihood: Input speed sensor failed
- Medium likelihood: Wiring or connector fault
Possible symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Diagnostic notes
- The malfunction indicator lamp may illuminate
- Reduced-power or limp mode may occur
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.