P0720 — Output Speed Sensor Circuit #

Note: The code’s description may vary depending on the vehicle manufacturer.

• Ford: Output Shaft Speed Sensor Circuit Malfunction
• Chrysler: Output Speed Sensor Circuit
• Honda: Transmission Countershaft Speed Sensor Circuit Malfunction
• Toyota: Output Speed Sensor Signal

Summary of DTC P0720 #

DTC P0720 is a generic OBD-II trouble code that signals an issue with the output speed sensor circuit in your vehicle’s automatic transmission. This sensor, sometimes called the output shaft speed (OSS) sensor, monitors the rotation speed of the transmission’s output shaft and relays that data to the engine control module (ECM) or transmission control module (TCM). If the ECM/TCM detects an abnormal or missing signal from this sensor, it logs the P0720 code. The output speed sensor is crucial for proper shifting, accurate speedometer readings, and overall transmission operation. Addressing this code promptly can prevent further drivability concerns.

Common Symptoms for Code P0720 #

When P0720 is set, your vehicle may display a range of drivability issues, though some symptoms can be subtle. Because the output speed sensor feeds vital data to the transmission and engine computers, problems often affect shifting and speedometer accuracy. Typical symptoms include:

• Erratic or harsh shifting between gears
• Speedometer not working or displaying incorrect speed
• Transmission stuck in a single gear (often “limp” mode)
• Check Engine Light illuminated
• Poor fuel economy
• Possible ABS or traction control warning lights (in some vehicles)

Probable Causes for Code P0720 #

P0720 can be triggered by several different issues, ranging from electrical faults to mechanical failures. The most common causes, listed in order of likelihood, are:

1. Faulty output speed sensor (sensor failure or internal short)
2. Damaged or corroded sensor wiring/connectors (open circuit, frayed wires, loose pins)
3. Transmission fluid contamination (debris interfering with sensor operation)
4. Failed or faulty ECM/TCM (rare, but possible)
5. Internal transmission problem (worn shafts/gears affecting sensor readings)

Step-by-Step Diagnosis for Code P0720 #

Accurately diagnosing P0720 requires a structured approach and basic diagnostic tools. Here’s how a technician or a well-equipped DIYer can proceed:

1. Connect a scan tool to verify the P0720 code and check for related transmission or sensor codes.
2. Visually inspect the output speed sensor and harness for obvious damage, loose connections, or corrosion.
3. Check the sensor’s electrical connector for bent pins or moisture intrusion.
4. Measure sensor resistance using a digital multimeter; compare readings to OEM specifications.
5. Backprobe the sensor harness to verify power supply and ground (as per OEM wiring diagram).
6. If available, monitor live data on the scan tool to view the output speed sensor signal while driving or turning the output shaft by hand (vehicle safely supported).
7. If all wiring and sensor tests pass, consider inspecting the transmission for internal issues or performing further testing on the ECM/TCM (as advised by OEM procedures).

Possible Repairs for Code P0720 #

Once you’ve identified the root cause, the following repairs are commonly performed to resolve P0720:

• Replace the faulty output speed sensor.
• Repair or replace damaged, corroded, or loose wiring/connectors at the sensor.
• Change contaminated transmission fluid and inspect for debris in the transmission pan.
• Repair or replace the ECM/TCM if it fails to process the sensor signal (rare, confirm with advanced diagnostics).
• Address internal transmission issues such as worn output shafts or gears, if confirmed during inspection.

Is It Safe to Drive with Code P0720? #

Driving with code P0720 is not recommended for extended periods. While the car may seem drivable, unresolved output speed sensor issues can cause improper shifting, loss of speedometer function, and can trigger limp mode, severely limiting vehicle speed and performance. In some cases, continued driving may lead to further transmission damage. If you experience harsh shifts or your vehicle is stuck in a single gear, have it inspected and repaired as soon as possible.

Vehicles Most Commonly Affected by Code P0720 #

P0720 is a generic OBD-II code and can affect many vehicles with automatic transmissions, but it is most commonly reported in:

• Ford (F-150, Explorer, Escape, Focus, Taurus)
• Chrysler/Dodge/Jeep (Grand Cherokee, Ram, Caravan, Charger)
• Honda (Accord, Odyssey, CR-V)
• Toyota (Camry, Corolla, Highlander, Tacoma)
• Nissan (Altima, Maxima, Pathfinder)

Common Mistakes & Best Practices for Code P0720 #

Even seasoned technicians can make errors when tackling P0720. Here’s what to watch for, and how to get it right:

• Replacing the output speed sensor without checking for wiring or connector problems.
• Ignoring signs of transmission fluid contamination (metal shavings or debris).
• Overlooking live data analysis; always confirm sensor operation in real time.
• Not following OEM testing procedures – always consult the service manual for precise specs and steps.
• Clearing the code before confirming a successful repair, which may mask intermittent problems.

Quick FAQ for Code P0720 #

Q: Will replacing the output speed sensor always fix code P0720?
A: Not always. While a failed sensor is common, wiring issues or internal transmission faults can also trigger P0720. Always perform a thorough diagnosis.

Q: Can a bad output speed sensor cause transmission slipping?
A: It can cause improper shifting or limp mode, but it won’t directly cause clutch or band slippage. If you experience slipping, there may be additional transmission issues.