In this blog, we’ll explore the causes, symptoms, and fixes for the P0720 code, and explain how the iCarsoft CR MAX Vehicle Diagnostic Tool from www.icarsoft-us.com can help you diagnose and resolve this issue effectively.

1. What Does P0720 Mean?

The P0720 code is a diagnostic trouble code (DTC) indicating "Output Speed Sensor Circuit Malfunction." This means there’s an issue with the output speed sensor (OSS), which monitors the rotational speed of the transmission output shaft. The Transmission Control Module (TCM) or Engine Control Unit (ECU) uses this data to control gear shifting and ensure proper transmission operation. When the TCM/ECU detects an incorrect signal or no signal from the OSS circuit, it triggers P0720, potentially affecting shifting performance.

2. Causes Behind P0720

Faulty Output Speed Sensor
A defective OSS may fail to send accurate speed data due to wear, damage, or internal failure.

Wiring or Connector Issues
Damaged, shorted, or corroded wiring or connectors in the OSS circuit can disrupt signal transmission.

Transmission Problems
Issues with the transmission, such as internal wear or fluid contamination, can affect the sensor’s readings.

TCM or ECU Malfunction
In rare cases, a fault in the TCM or ECU may misinterpret the OSS signals.

3. Reasons for P0720 Occurrence

Sensor Wear
High mileage or exposure to transmission heat and fluid can degrade the OSS over time, causing circuit issues.

Physical Damage
Impact damage or improper handling during repairs can harm the sensor or its wiring.

Fluid Contamination
Dirty or low transmission fluid can interfere with the sensor’s operation and lead to malfunctions.

4. Vehicles Prone to P0720

The P0720 code can affect any OBD-II vehicle with an automatic transmission, including brands like Chevrolet, Ford, Toyota, Honda, and Nissan. European models such as BMW, Audi, and Volkswagen are also susceptible, particularly those with high mileage or heavy-duty transmission use.

5. Severity of P0720

The P0720 code is of moderate to high severity. It can cause erratic shifting, transmission slipping, or even a failure to shift gears, which may lead to unsafe driving conditions or further transmission damage if not addressed.

6. Driving with P0720 Active

Driving with P0720 is not recommended. The issue can result in unpredictable transmission behavior, such as harsh shifting, delayed shifts, or the transmission entering limp mode, posing a safety risk. It’s best to resolve the problem promptly.

7. DIY Solutions for P0720

Sensor Replacement
Replace the faulty OSS with a compatible unit, following your vehicle’s repair manual.

Wiring Repair
Inspect and fix any damaged, shorted, or corroded wiring and connectors in the sensor circuit.

Transmission Fluid Check
Inspect and replace dirty or low transmission fluid to ensure proper sensor operation.

8. How to Diagnose P0720

Scan Tool
Use the iCarsoft CR MAX to read the P0720 code and monitor live data from the OSS to check for signal irregularities.

Multimeter Testing
Measure the sensor’s voltage and resistance, comparing them to manufacturer specifications.

Visual Inspection
Check the sensor, wiring, and transmission for visible damage or fluid leaks.

9. Cost of Fixing P0720

Repair costs vary. An OSS replacement costs $30-$150, with labor adding $50-$150 (1-2 hours at $75/hour), totaling $80-$300. Wiring repairs range from $50-$200, while transmission fluid changes or more extensive repairs may cost $100-$500.

10. Clearing P0720 from Your System

Using a Scan Tool
Connect the iCarsoft CR MAX to clear the code and verify the repair.

Battery Disconnection
Disconnect the battery for 5-10 minutes to reset the TCM/ECU, though this may not address the root cause.

11. Preventing P0720 Recurrence

Regular Maintenance
Inspect the transmission system and fluid levels during routine service to catch issues early.

Quality Parts
Use high-quality OSS units to ensure reliable performance.

Fluid Maintenance
Regularly change transmission fluid to prevent contamination and wear on sensors.

12. Notes on P0720

Related Codes
P0720 may appear with P0715 (input speed sensor circuit) or P0730 (incorrect gear ratio). Diagnose together.

Transmission Impact
Since P0720 affects shift timing, it directly influences transmission performance and vehicle safety.

13. Diagnostic Tools for P0720

The iCarsoft CR MAX from www.icarsoft-us.com is perfect for tackling P0720. It reads the code, provides live sensor data, and helps identify circuit or transmission issues. After repairs, it clears the code and confirms the fix.

Want to resolve P0720 quickly? The iCarsoft CR MAX simplifies diagnostics and ensures smooth transmission performance.