OBD-II Code P0720 — What It Means & How to Fix It

What Does This Error Mean?

P0720 means the output speed sensor circuit has a malfunction. The output speed sensor measures how fast the transmission output shaft is spinning. This tells the TCM how fast the car is actually moving — and is used for shift control, speedometer input, and ABS on some vehicles. When this sensor fails, the transmission may shift harshly, at the wrong times, or not at all. Your speedometer may also stop working depending on how your vehicle uses this sensor.

Affected Models

All vehicles 1996+ with automatic transmission
Common in Chrysler, Dodge, and Jeep vehicles
Common in Ford and Lincoln vehicles
Common in GM vehicles
Common in Nissan and Infiniti vehicles

Common Causes

Faulty output speed sensor that has failed electrically
Damaged tone ring (reluctor wheel) on the output shaft that the sensor reads
Corroded or damaged wiring to the sensor
Corroded sensor connector at the transmission
Metal debris on the sensor tip interfering with the signal

How to Fix It

Use a scan tool to check the output speed sensor reading. With the car moving at a known speed, the output speed should show a matching value. A zero reading while moving confirms sensor failure.

Compare output speed to vehicle speed on the scan tool — they should closely match.
Locate the output speed sensor on the transmission. It is typically on the rear of the transmission or transfer case on 4WD vehicles. Check its connector for corrosion.

On 4WD vehicles there may be additional speed sensors for the transfer case.
Inspect the wiring from the sensor to the TCM. Look for any damaged areas, especially near the exhaust and any flexible sections of the harness.

Output shaft sensor wiring can be damaged by road debris since it is often located on the underside of the transmission.
Remove the sensor and inspect the tip for metal shavings or debris. Clean with a rag if dirty. Also visually inspect the tone ring on the output shaft for broken or missing teeth.

A damaged tone ring requires internal transmission repair — not something you can fix from the outside.
Replace the sensor if faulty. Reinstall with a new O-ring if included. Clear the code and test drive to verify smooth shifting and correct speedometer operation.

After clearing the code, take the car on a highway drive to let the TCM complete its full shift adaptation learning.

When to Call a Professional

Output speed sensor replacement is often a DIY-accessible repair. Sensors cost $20 to $80 for the part. On many vehicles the sensor threads into the transmission case and can be swapped without major disassembly. Labor at a shop is $100 to $200. If the tone ring is damaged, transmission internal repair may be required.

Frequently Asked Questions

Will P0720 affect my speedometer?

It depends on the vehicle. On older vehicles, the output speed sensor directly drives the speedometer. On newer vehicles, the speedometer may use separate wheel speed sensors from the ABS system. Check whether your speedometer stops working with P0720 active — if yes, the output sensor feeds your speedometer.

Can P0720 cause transmission damage?

Not directly, but indirectly yes. With no output speed signal, the TCM cannot calculate the correct gear ratio. This causes improper shifting that can stress the transmission over time. Get it repaired promptly to avoid accelerating wear.

Is the output speed sensor inside or outside the transmission?

On most vehicles, it is external — it threads into the transmission case from the outside. You can often see it without getting under the car, depending on the vehicle. On some older transmissions, it is inside the pan. Check your repair manual to confirm.