P0720 Code: Output Speed Sensor — Meaning & Fix

Sun West Transmissions — Glendale, AZ. Free estimates, honest diagnosis and a 3-year / 40,000-mile warranty on qualifying rebuilds and replacements.

The P0720 code stands for “Output Speed Sensor Circuit Malfunction.” The output speed sensor measures how fast the transmission output shaft is turning, which is directly tied to how fast the vehicle is moving. On many vehicles, that same signal feeds the speedometer, cruise control and other systems. So when it fails, drivers often notice more than just shifting problems.

Sun West Transmissions in Glendale diagnoses P0720 on trucks, SUVs and cars. Here is what the code means and what to expect.

What the Output Speed Sensor Does

The output speed sensor reads a toothed wheel or ring on the output shaft or a rotating component near the rear of the transmission. On rear-wheel-drive trucks it is often in the tail housing or case extension; on front-wheel-drive transaxles it is typically on the case near the differential or final drive.

The transmission computer uses output speed to decide when to shift, to calculate gear ratio along with input speed, and to manage torque converter clutch apply. Some vehicles use wheel speed sensors as a backup or primary reference, while others rely heavily on the output sensor.

Common Symptoms of P0720

• Check engine light, often with P0700
• Speedometer that reads zero, jumps around or drops out
• Erratic, late or harsh shifts, or no upshifts
• Transmission stuck in one gear or in limp mode
• Cruise control not working
• Harsh downshifts when coming to a stop
• On some vehicles, ABS or traction control lights

Common Causes of P0720

Failed Sensor

The sensor can fail from heat, age or internal shorting. External sensors are exposed to road debris and heat from nearby exhaust components.

Metal Debris

Magnetic sensors attract fine metal particles from normal wear. Heavy buildup can weaken or distort the signal. It is also a sign the transmission should be inspected for wear.

Wiring and Connectors

Harnesses near the tail housing can rub on brackets or get damaged by heat. Connectors can corrode or loosen. Fluid leaking into connectors can cause intermittent faults. See transmission leak repair if a leak is involved.

Damaged Reluctor Ring

If the ring the sensor reads is cracked, loose or damaged, the signal will be erratic even with a new sensor. Some designs use a reluctor pressed onto the output shaft or part of the parking gear.

Internal Electronics or Module

Some transmissions route output speed through internal harnesses or modules. A fault there can set P0720 without an external problem.

What You Can Safely Check

1. Watch the speedometer. If it drops out at the same time shifting goes wrong, the output speed signal is a strong suspect.
2. Check transmission fluid level and condition if your vehicle allows.
3. Look for obvious damage to the sensor wiring near the transmission, only if you can do so safely.
4. Note whether problems come and go with bumps or heat.

If your speedometer is not working, be extra careful about your speed, and avoid using cruise control until repaired.

How We Diagnose and Fix P0720

At our Glendale shop, we read all modules, review freeze-frame data and compare output speed with wheel speed and input speed on a scan tool during a road test. A signal that drops to zero or jumps while the vehicle speed is steady shows where the problem lies. We test the sensor and circuit, inspect connectors, and check the sensor tip for debris. If needed, we inspect the reluctor. See computer transmission diagnostics.

Many P0720 repairs involve an external sensor and wiring and do not require removing the transmission. When debris levels suggest internal wear, we explain whether a transmission service or a rebuild makes sense.

Is It Safe to Drive With P0720?

A vehicle with P0720 may shift unpredictably and may not show your true speed. Short, careful trips to the shop are usually possible if the vehicle is in limp mode and drives predictably. Avoid freeways, towing and long drives. If harsh downshifts are jolting the vehicle or the transmission slips, stop driving.

Related Codes

P0720 is often paired with input speed codes like P0715 when a shared wiring issue or internal module is involved, and can lead to ratio codes like P0730 because the computer cannot calculate gear ratio correctly.

P0720 Code FAQ

Why does my speedometer stop working with P0720?

On many vehicles, the speedometer uses the output speed sensor signal. When it fails, the speedometer often drops out.

Is the output speed sensor the same as the vehicle speed sensor?

On many vehicles, yes. Some designs use wheel speed sensors for vehicle speed instead, so it varies.

How much does it cost to fix P0720?

It depends on the vehicle and the cause. Call (623) 473-9800 for a free estimate.