How to Fix P0700 Code: Understanding the Transmission Control System (MIL Request)

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September 19, 2023
How to Fix P0700 Code: Understanding the Transmission Control System (MIL Request)

In the world of automotive diagnostics, the check engine light can often be a source of concern for drivers. One common culprit behind this warning is the P0700 code, signifying a "Transmission Control System (MIL Request)." In this blog post, we'll delve into the P0700 code, decipher its meaning, and explore its significance in various car makes, including Chevy, Subaru, and Dodge.

Decoding the P0700 Code

The P0700 code is part of the OBD-II (On-Board Diagnostics) system, serving as a generic diagnostic trouble code (DTC) shared by multiple car manufacturers. It's essentially a request from the Transmission Control Module (TCM) to the Engine Control Module (ECM) or Powertrain Control Module (PCM) to illuminate the check engine light (MIL) due to detected issues within the transmission system.

Common Causes of the P0700 Code

The P0700 code can be triggered by a range of factors, including:

  • Faulty Transmission Control Module (TCM): A malfunctioning TCM can send erroneous signals or fail to communicate properly with the ECM or PCM.
  • Transmission Sensor Issues: Problems with transmission speed sensors, range sensors, or other sensors within the transmission system can lead to this code.
  • Wiring or Connector Problems: Damaged or corroded wiring, connectors, or harnesses between the TCM and ECM/PCM can disrupt communication.
  • Transmission Solenoid Malfunctions: Issues with transmission solenoids, responsible for controlling fluid flow, can trigger the code.
  • Low Transmission Fluid Level: A low transmission fluid level or dirty fluid can lead to transmission issues, causing the P0700 code to appear.

P0700 Code in Different Car Makes

Let's explore how the P0700 code can affect various car makes:


Chevrolet vehicles may experience the P0700 code due to problems with the TCM, transmission sensors, or wiring issues. Regular maintenance and timely diagnosis are essential for addressing this code in Chevy vehicles.


Subaru cars can also encounter the P0700 code, often caused by TCM malfunctions, sensor issues, or wiring problems. Subaru owners should consult a professional mechanic to diagnose and resolve this code effectively.


Dodge vehicles might trigger the P0700 code due to a range of factors, including TCM problems, transmission sensor issues, or solenoid malfunctions. Timely inspection and repairs are critical for Dodge owners.

Responding to the P0700 Code

If your check engine light comes on with a P0700 code, consider the following steps:

  • Diagnostic Scan: Have your vehicle scanned by a professional mechanic to confirm the P0700 code.
  • Inspect TCM and Sensors: Check the TCM, transmission speed sensors, and other transmission sensors for faults. Replace as needed.
  • Check Wiring and Connectors: Examine wiring, connectors, and harnesses for damage or corrosion. Repair or replace as necessary.
  • Transmission Fluid Inspection: Ensure the transmission fluid level is adequate and clean. Top up or perform a fluid change if required.
  • Clear the Code: After making necessary repairs, clear the code from the vehicle's computer using an OBD-II scanner.

Wrap Up

In conclusion, the P0700 code indicating a "Transmission Control System (MIL Request)" is a common concern among drivers of various car makes, including Chevy, Subaru, and Dodge. Regardless of your vehicle's brand, understanding the potential causes and taking prompt action can help maintain your transmission's performance and prevent further damage. Regular maintenance and addressing issues within the transmission system are essential for resolving the P0700 code and ensuring your vehicle's smooth operation.

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