Faulty output shaft speed sensor (both sources). Damaged, loose or dirty wiring or connectors in the sensor circuit (both sources). Worn or missing teeth on the plastic drive gear that some OSS sensors use (OBD-Codes.com diagnostic notes). Faulty transmission fluid temperature sensor on vehicles where it shares the circuit with the OSS sensor (OBD-Codes.com). Defective shift solenoids, valve body, or engine coolant temperature sensor (RepairPal). Dirty transmission fluid restricting hydraulic passages (RepairPal). The sources differ on causes: OBD-Codes.com lists only the sensor, wiring and the TFT sensor, while RepairPal also lists shift solenoids, the valve body, the coolant temperature sensor and dirty fluid, and says the code often implies a slipping transmission.

Repair damaged wiring or connectors in the output speed sensor circuit. Replace a worn sensor drive gear, or replace the output speed sensor if it tests out of spec (OBD-Codes.com). Replace the transmission fluid temperature sensor if it shares the circuit and tests bad (OBD-Codes.com). Repair shift solenoids, the valve body or fluid problems if diagnosis points there (RepairPal).

P0720🔧 Transmission / Speed sensingStop and fix promptly

P0720: Output Speed Sensor Circuit Malfunction (Meaning, Causes, Fixes)

Q: What does P0720 mean?

P0720 means the engine or transmission computer has found a problem with the transmission's output shaft speed sensor signal. The computer uses that signal for shift timing and often for the speedometer. Common causes are a failed output speed sensor or damaged wiring or connectors, though RepairPal says it can also point to a slipping transmission. The output shaft speed (OSS) sensor sits at the end of the transmission, before the drive axles or driveshaft, and reads how fast the output shaft is spinning. OBD-Codes.com says the computer uses it to decide shift scheduling, torque converter engagement and electronic pressure control (EPC), and that it is commonly used for the speedometer too. OBD-Codes.com describes P0720 as the powertrain or engine control module (PCM/ECM) detecting a malfunction with the OSS sensor; the computer may substitute values from other sensors when the OSS signal is unavailable. RepairPal defines it a bit more broadly: the PCM is not seeing a rational speed signal from the output sensor, or there is a greater than specified RPM difference between the input and output speed sensors, during shifts or at steady speed. RepairPal says this often implies the transmission is slipping, while OBD-Codes.com treats it mainly as a sensor or circuit fault. OBD-Codes.com also notes that on some vehicles the OSS sensor is wired in line with the transmission fluid temperature (TFT) sensor, so a TFT fault can make the OSS signal fail too. It is a generic OBD-II code, though repair steps vary by make and model. Related codes are P0721 (range/performance), P0722 (no signal) and P0723 (intermittent).

Q: Can I keep driving with P0720?

Stop and fix promptly. Get it diagnosed soon and drive gently until you do. RepairPal rates P0720 Urgent, meaning it can cause severe damage or be unsafe, and says it often implies the transmission is slipping. Both sources list shifting problems: OBD-Codes.com mentions delayed shifts and a dead speedometer, and RepairPal says the car may not shift properly and some cars stall when coming to a stop after freeway driving. If the transmission slips, shifts harshly, or the car stalls, avoid highway driving and have it checked.

Reviewed 2026-10-22 · Based on 2 cited source(s)

What P0720 means

The output shaft speed (OSS) sensor sits at the end of the transmission, before the drive axles or driveshaft, and reads how fast the output shaft is spinning. OBD-Codes.com says the computer uses it to decide shift scheduling, torque converter engagement and electronic pressure control (EPC), and that it is commonly used for the speedometer too. OBD-Codes.com describes P0720 as the powertrain or engine control module (PCM/ECM) detecting a malfunction with the OSS sensor; the computer may substitute values from other sensors when the OSS signal is unavailable. RepairPal defines it a bit more broadly: the PCM is not seeing a rational speed signal from the output sensor, or there is a greater than specified RPM difference between the input and output speed sensors, during shifts or at steady speed. RepairPal says this often implies the transmission is slipping, while OBD-Codes.com treats it mainly as a sensor or circuit fault. OBD-Codes.com also notes that on some vehicles the OSS sensor is wired in line with the transmission fluid temperature (TFT) sensor, so a TFT fault can make the OSS signal fail too. It is a generic OBD-II code, though repair steps vary by make and model. Related codes are P0721 (range/performance), P0722 (no signal) and P0723 (intermittent).

Severity: can I keep driving?

Stop and fix promptly

Get it diagnosed soon and drive gently until you do. RepairPal rates P0720 Urgent, meaning it can cause severe damage or be unsafe, and says it often implies the transmission is slipping. Both sources list shifting problems: OBD-Codes.com mentions delayed shifts and a dead speedometer, and RepairPal says the car may not shift properly and some cars stall when coming to a stop after freeway driving. If the transmission slips, shifts harshly, or the car stalls, avoid highway driving and have it checked.

Common symptoms

Check engine light on (both sources)
Delayed shifts (OBD-Codes.com) or the transmission not shifting properly (RepairPal)
Speedometer not working (OBD-Codes.com)
Lower fuel economy (RepairPal)
Stalling when coming to a stop after freeway driving, or misfire-like symptoms in some cases (RepairPal)
Occasionally no noticeable symptoms (RepairPal)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Faulty output shaft speed sensor (both sources)
Damaged, loose or dirty wiring or connectors in the sensor circuit (both sources)
Worn or missing teeth on the plastic drive gear that some OSS sensors use (OBD-Codes.com diagnostic notes)
Faulty transmission fluid temperature sensor on vehicles where it shares the circuit with the OSS sensor (OBD-Codes.com)
Defective shift solenoids, valve body, or engine coolant temperature sensor (RepairPal)
Dirty transmission fluid restricting hydraulic passages (RepairPal)
The sources differ on causes: OBD-Codes.com lists only the sensor, wiring and the TFT sensor, while RepairPal also lists shift solenoids, the valve body, the coolant temperature sensor and dirty fluid, and says the code often implies a slipping transmission

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes and write down the freeze frame data. If there is also a transmission fluid temperature sensor code, OBD-Codes.com says to suspect either sensor or the wiring between them.
Check for technical service bulletins (TSBs) for your vehicle; there may be a known fix.
Inspect the output speed sensor's wiring harness and connector for damage, loose connections or dirty terminals.
Check the transmission fluid level and condition; RepairPal lists dirty fluid as a possible cause.
If your sensor uses a plastic drive gear, OBD-Codes.com suggests removing the sensor and checking the gear for worn or missing teeth. Be careful of hot transmission fluid.

Typical fixes

Repair damaged wiring or connectors in the output speed sensor circuit
Replace a worn sensor drive gear, or replace the output speed sensor if it tests out of spec (OBD-Codes.com)
Replace the transmission fluid temperature sensor if it shares the circuit and tests bad (OBD-Codes.com)
Repair shift solenoids, the valve body or fluid problems if diagnosis points there (RepairPal)

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

The transmission is slipping, shifting harshly, or the car stalls when coming to a stop
Testing needs the factory shop manual's resistance specs, a digital multimeter, and a graphing meter or oscilloscope to check the signal while the vehicle is moving (OBD-Codes.com)
RepairPal says P0720 can be hard to catch and recommends a test drive watching output speed against engine load, throttle position, RPM and road speed
The wiring and sensor check out and the code comes back, which points to a problem inside the transmission

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P0720 serious?

Treat it as serious. RepairPal rates it Urgent and says it often implies the transmission is slipping. Drive gently and get it diagnosed soon.

Can P0720 make my speedometer stop working?

Yes. OBD-Codes.com says the output speed sensor is commonly used for the speedometer and lists a speedometer that doesn't work as a symptom.

Is P0720 always a bad sensor?

No. Both sources list the sensor and its wiring, but RepairPal also lists shift solenoids, the valve body, dirty fluid and a slipping transmission, and OBD-Codes.com notes a shared transmission fluid temperature sensor can cause it. Test before replacing parts.

How much does it cost to fix P0720?

Neither source gives a repair cost. The price depends on whether it's wiring, the sensor, or a deeper transmission problem, so get a diagnosis or a written estimate before replacing parts.

Sources

Last reviewed 2026-10-22. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.