P0720 Code: Here's How to Solve It Fast

The P0720 trouble code is a diagnostic trouble code (DTC) that indicates a malfunction in the output speed sensor circuit. Specifically, it signals that the Powertrain Control Module (PCM) has detected an issue with the output shaft speed sensor (OSS), which plays a critical role in the vehicle's transmission system. This code is commonly associated with transmission performance problems, as the OSS provides essential data about the rotational speed of the transmission output shaft. When this data is inaccurate or erratic, it can lead to various driving issues, including improper gear shifts and malfunctioning speedometers.

P0720 Code Meaning	P0720 Code Common Causes
Output Speed Sensor Circuit Malfunction	Faulty output shaft speed sensor
Transmission performance issues	Open or short in the electrical wiring
Erratic or insufficient input from OSS	Malfunctioning Powertrain Control Module (PCM)
Inaccurate vehicle speed readings	Contaminated or old transmission fluid
Delayed or harsh gear shifts	Damaged transmission internals

Symptoms of P0720 Code

When the P0720 code is triggered, vehicle owners may experience several symptoms that can affect drivability and safety. Recognizing these symptoms early can help in diagnosing and addressing the underlying issues.

Symptoms

• Delayed or No Gear Shifting: The vehicle may exhibit delays in shifting gears or may not shift at all, leading to poor acceleration.
• Malfunctioning Speedometer: The speedometer may provide inaccurate readings or fail to function entirely, complicating speed regulation.
• Cruise Control Malfunction: The cruise control system may not engage or may disengage unexpectedly, impacting driving comfort.
• Check Engine Light Illuminated: The vehicle's dashboard will typically display the check engine light when this code is active.
• Stalling: The vehicle may stall when coming to a stop, especially if there are severe transmission issues.

Detailed Diagnosis of P0720 Code

Diagnosing the P0720 code involves a systematic approach to identify the root cause of the malfunction. Here’s a step-by-step guide to help you through the diagnosis process.

Step-by-Step Diagnosis

1. Use an OBD-II Scanner: Start by connecting an OBD-II scanner to your vehicle's diagnostic port to confirm that the P0720 code is present. Note any additional codes that may accompany it.
2. Visual Inspection: Perform a visual inspection of the wiring harness and connectors associated with the OSS. Look for signs of damage, corrosion, or loose connections.
3. Check Output Speed Sensor: Test the output speed sensor for proper operation using a multimeter. Check for resistance and ensure it falls within manufacturer specifications.
4. Inspect Wiring: Check for continuity in the wiring between the OSS and PCM. Look for open circuits or shorts that could disrupt signal transmission.
5. Transmission Fluid Condition: Inspect the transmission fluid for contamination or degradation. Old or contaminated fluid can affect sensor performance.
6. PCM Functionality: If all other components test fine, consider testing or replacing the PCM, as it may not be processing information correctly.

Solution Methods for P0720 Code

Once you have diagnosed the issue causing the P0720 code, you can proceed with appropriate solutions based on your findings.

Solution Methods

• Replace Faulty Output Speed Sensor: If testing reveals that the OSS is defective, replacing it is often necessary. Ensure you use a quality replacement part.
• Repair Electrical Wiring: If you find damaged wiring or connectors, repair or replace them as needed to restore proper electrical function.
• Change Transmission Fluid: If old or contaminated fluid is identified as an issue, perform a transmission fluid change to ensure optimal performance.
• Reprogram or Replace PCM: If all else fails and you suspect PCM malfunction, consult with a professional mechanic about reprogramming or replacing it.

Cost Estimates

The cost of repairs related to the P0720 code can vary significantly based on labor rates and parts prices:

• Output Speed Sensor Replacement: $100 - $300 (parts and labor)
• Electrical Repairs: $50 - $200 (depends on extent of damage)
• Transmission Fluid Change: $100 - $200
• PCM Replacement/Reprogramming: $300 - $1,500 (depending on vehicle make/model)

Warnings and Recommendations

Important Warnings:

• Always disconnect the battery before working on electrical components to prevent shorts.
• If you are not confident in your ability to diagnose or repair issues related to this code, seek professional assistance to avoid further damage to your vehicle.

Closing Thoughts

The P0720 trouble code indicates significant issues related to your vehicle's output speed sensor circuit. Understanding its implications and symptoms can empower vehicle owners and DIY mechanics alike to tackle these problems effectively. By following a systematic diagnostic approach and addressing any identified issues promptly, you can restore your vehicle's performance and ensure safe driving conditions.

Frequently Asked Questions About P0720

• What does the P0720 code mean?
  The P0720 code indicates a malfunction in the output speed sensor circuit, affecting transmission performance.
• What are common symptoms of a P0720 code?
  Common symptoms include delayed gear shifting, malfunctioning speedometer, and illuminated check engine light.
• Can I fix the P0720 code myself?
  If you have basic mechanical skills and tools, you can diagnose and potentially fix some issues related to this code.
• What should I do if my check engine light is on?
  You should scan your vehicle for codes using an OBD-II scanner and investigate any active codes.
• How much does it cost to fix a P0720 code?
  The cost can range from $100 for minor repairs to over $1,500 for PCM replacement.
• Is it safe to drive with a P0720 code?
  It’s advisable not to drive until you address this issue as it can lead to further transmission problems.
• What causes a P0720 code?
  A faulty output speed sensor, damaged wiring, or malfunctioning PCM are common causes.
• When should I seek professional help?
  If you're unable to diagnose or fix the issue after following steps outlined above, consult a professional mechanic.