Summary
P0715 means the transmission control module (TCM) can't read the input shaft (turbine) speed sensor signal. This sensor tells the TCM how fast the torque converter's turbine is spinning — critical data for calculating gear ratios and shift timing. Without it, the TCM can't verify shifts are happening correctly and will often trigger limp mode. The most common cause is a failed speed sensor (45%), followed by wiring issues (25%) and sensor contamination (15%).
Severity: Moderate to High — shifts become unpredictable without this data
Safe to drive: Drive with caution — limp mode likely, avoid highway driving
Repair cost: $30–$800+ depending on cause
DIY difficulty: Moderate
What does P0715 mean?
The input speed sensor (also called the turbine speed sensor) sits on or inside the transmission and reads the rotational speed of the input shaft — the shaft connected to the torque converter turbine. The TCM uses this reading along with the output speed sensor to calculate the actual gear ratio and compare it to the commanded gear.
When the TCM gets no signal, an erratic signal, or a signal outside its expected range from the input speed sensor circuit, it sets P0715. Without reliable input speed data, the TCM can't confirm gear changes are happening properly, can't calculate torque converter slip, and often defaults to limp mode (locked in one gear) as a protective measure.
You'll typically notice harsh or delayed shifts, the transmission stuck in one gear, or the speedometer acting erratically on some vehicles where the input speed sensor feeds that data.