How much does it cost to fix P0720?

DIY repair typically costs $40–$150 for parts. Professional repair runs $150–$450 including parts and labor.

P0720

Powertrain

Moderate

Output Speed Sensor Circuit Malfunction

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OBD2 code P0720, "Output Speed Sensor Circuit Malfunction," indicates that your vehicle's powertrain control module (PCM) has detected an abnormal signal from the transmission output speed sensor. This sensor monitors the rotational speed of the transmission's output shaft and sends this critical data to the PCM, which uses it to control transmission shift points, speedometer readings, and cruise control operation. When the PCM receives an erratic, missing, or out-of-range signal from this sensor, it triggers the P0720 code and illuminates your Check Engine Light.

This code matters because your transmission relies on accurate speed data to shift smoothly and efficiently. Without proper output speed sensor function, your transmission may shift harshly, stay stuck in one gear (often second or third gear in "limp mode"), or experience delayed engagement. You may also notice your speedometer behaving erratically or not working at all, and your cruise control may refuse to engage. Continuing to drive with this issue can lead to increased transmission wear and potentially more expensive repairs down the line, as the transmission control system cannot properly adapt shift timing to driving conditions.

If you've received a P0720 code, you should address it within a few days to prevent further transmission problems. In most cases, the fix involves replacing the output speed sensor itself, which typically costs between $40-$150 for DIY repairs or $150-$450 at a professional shop. Before replacing the sensor, it's wise to inspect the wiring and connectors for damage or corrosion, and check your transmission fluid level and condition. Many moderately skilled home mechanics can tackle this repair, as the sensor is often accessible from underneath the vehicle, though the exact location varies by make and model. Always verify the diagnosis with a proper scan tool and visual inspection before ordering parts.

Severity

Moderate — Address SoonWithin a few days

Symptoms

•Erratic or inaccurate speedometer readings
•Transmission shifting harshly or slipping between gears
•Check Engine Light illuminated on dashboard
•Transmission stuck in one gear (limp mode)
•Poor fuel economy due to improper shift timing
•Cruise control not functioning or disengaging unexpectedly

Likely Causes

Faulty output speed sensor (OSS)45%

The output speed sensor itself has failed due to wear, heat exposure, or internal electrical failure, preventing it from sending accurate signals to the transmission control module.

Damaged or corroded wiring and connectors30%

The electrical connections or wiring harness leading to the output speed sensor may be damaged, corroded, or loose, interrupting the signal transmission to the PCM.

Low transmission fluid level or contaminated fluid15%

Insufficient or dirty transmission fluid can affect sensor operation and cause erratic readings, as the sensor relies on fluid flow and proper lubrication to function correctly.

Transmission control module (TCM) failure7%

The transmission control module itself may be malfunctioning and unable to properly receive or process signals from the output speed sensor.

Mechanical transmission issues or worn gears3%

Internal transmission damage or worn components can affect the sensor's ability to accurately detect output shaft speed, though this is less common as a direct cause of P0720.