OBD-II Code P0790 – Normal/Performance Switch Circuit: Understanding and Repairing the Issue
When the check engine light comes on, it can be a cause for concern for many car owners. The OBD-II system is a diagnostic tool that monitors the vehicle’s emission system and communicates the issue with the car’s computer. One of the many codes generated by the system is the P0790 code, which indicates a problem with the normal/performance switch circuit. In this article, we will take a closer look at what the P0790 code is, its potential causes, and how to repair the issue.
Understanding the P0790 Code
The P0790 code is a generic trouble code that signifies a problem with the normal/performance switch circuit. This code is often associated with Automatic Transmission Control Module (TCM) issues, and it is typically displayed in vehicles that have an automatic transmission. Vehicles with a manual transmission do not have a normal/performance switch, which means that this code will not be applicable to them.
When the P0790 code appears, it indicates that there is a circuit malfunction associated with the switch that differentiates the normal mode from the performance mode of the transmission. In many cases, the transmission will not shift correctly, which can lead to decreased fuel economy, a reduction in performance, and additional wear on the transmission.
Potential Causes of the P0790 Code
The P0790 code is relatively rare, and it is usually caused by a fault in the transmission’s normal/performance switch circuitry. Here are some of the most common causes of the P0790 code:
1. Malfunctioning Switch: The normal/performance switch can fail, which will cause the transmission to remain in one gear.
2. Short in the Wiring: Any short in the wiring leading to the switch can cause this code to appear.
3. Faulty TCM: The TCM is responsible for monitoring the transmission’s performance and controlling the switch circuit, and if it is defective, it can cause the P0790 code to appear.
4. Loose or Corroded Connections: Loose or corroded connections within the switch circuit can cause the code to appear.
Diagnosing and Repairing the P0790 Code
The P0790 code can be challenging to diagnose and repair, and a professional mechanic should handle the task to avoid making the problem worse. Here are the steps that a mechanic may take:
1. Retrieve the Code: The first step is to retrieve the P0790 code using an OBD-II scanner. This scanner will provide further information regarding the problem and enable the mechanic to begin troubleshooting the issue.
2. Examine the Wiring: The mechanic will inspect the wiring in the switch circuit for any issues (e.g., short circuits or loose connections). They will repair or replace any damaged wires, connectors, or terminals as necessary.
3. Inspect the Normal/Performance Switch: The mechanic will test the switch to verify that it is functioning correctly. They may replace the switch if it is malfunctioning or damaged.
4. Check the TCM: If the switch and wiring are working correctly, the mechanic will inspect the TCM. They will confirm that the module receives appropriate power and ground, examines the data stream to check for missing inputs, and test switches and solenoids as applicable.
5. Clear the Code and Test Drive: After repairing the underlying issue, the mechanic will clear the code and test drive the vehicle to ensure that the issue has been resolved.
FAQs
1. What are some symptoms of a faulty normal/performance switch?
A: The most common symptom associated with a faulty switch is an inability to switch between normal and performance modes.
2. What is the typical cost to fix the P0790 code?
A: The cost of fixing this issue can vary depending on the underlying cause of the problem. In most cases, the cost will typically run between $200 and $500.
3. Can I drive my car when the P0790 code is displayed?
A: If you are still able to shift gears and the vehicle is not displaying any additional symptoms, it is usually safe to drive your vehicle for a short distance. However, it is always best to take your car to a mechanic as soon as possible to avoid potential issues down the road.
4. Can I fix the P0790 code by myself?
A: Unless you have a mechanical background, it is generally not recommended to try to fix the P0790 code yourself. This issue requires specialized knowledge, and any attempt to repair the problem can cause additional harm to your vehicle.
5. How can I prevent the P0790 code from appearing in the future?
A: There is no surefire way to prevent the P0790 code from appearing; however, you can prevent transmission issues by having regular maintenance check-up on your vehicle.
Conclusion
The P0790 code signifies that there is an issue with the normal/performance switch circuit. It is a relatively rare issue caused by a failure in the switch, short circuit in the wiring, or a defective TCM. Although this code may seem complex, a professional mechanic can diagnose and repair the issue using an OBD-II scanner, inspecting the wiring, testing the switch, checking the TCM, and clearing the code after fixing the problem. If you experience any symptoms or issues associated with the P0790 code, it is recommended that you take your vehicle to a mechanic to avoid potential damage.