P0720: Output Speed Sensor Circuit Malfunction

P0720 means the transmission control module is not receiving a proper signal from the output speed sensor. This sensor measures how fast the transmission output shaft rotates, which determines vehicle speed and helps the TCM calculate gear ratios and shift points.

P0720 is a transmission-related diagnostic trouble code classified as high severity. When your vehicle's ECU detects this condition, it stores P0720 and illuminates the check engine light.

If your vehicle has triggered P0720, you may notice one or more of these symptoms:

• Check engine light and transmission warning light on
• Speedometer not working or reading incorrectly
• Harsh or delayed gear shifts
• Transmission stuck in limp mode
• ABS or traction control warning lights on
• Cruise control disabled

Here are the most common causes of P0720, ranked by how likely they are to be the culprit:

No - address this immediately. Without a valid output speed signal, the transmission cannot manage shift timing and the speedometer may read incorrectly. This affects ABS and stability control systems as well. Drive only to a garage.

Follow these steps to pinpoint the root cause of P0720:

1. Check if the speedometer is working. A dead speedometer alongside P0720 strongly points to the output speed sensor, since both the transmission and instrument cluster rely on this signal.
2. Locate the output speed sensor on the transmission housing (typically near the tail shaft or differential housing). Inspect the connector for corrosion, loose pins, or damage.
3. Measure sensor resistance with a multimeter and compare to manufacturer specifications (typically 300-1200 ohms). Also check for signal voltage while spinning the sensor manually if accessible.
4. Use a scanner to monitor live data and compare input speed versus output speed readings. The output speed should correlate with vehicle speed and the current gear ratio.
5. If the sensor and wiring test normal, inspect the transmission fluid for metal contamination. Debris on the magnetic sensor tip can cause signal distortion.

Repair costs for P0720 vary depending on the root cause and your vehicle. Here are typical estimates:

P0720 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0720 or indicate related issues: