Understand and Fix P0734: Gear 3 Incorrect Ratio

Is your car displaying the error code P0734, indicating a “Gear 3 Incorrect Ratio” issue? If so, don’t panic. In this article, we’ll help you understand what this error code means, explore the potential causes behind it, and guide you through the steps to fix it.

Whether you’re a car enthusiast or a DIY enthusiast, we’ll provide you with detailed instructions, step-by-step guides, and useful tips to address the issue at hand.

Introduction to P0734 Error Code

The P0734 error code is specific to vehicles with automatic transmissions. It indicates that the transmission is not shifting correctly into the third gear. This can result in issues such as poor acceleration, reduced fuel efficiency, and increased transmission wear. It’s important to address this error code promptly to avoid further damage to your vehicle’s transmission system.

Understanding Gear Ratios in Automatic Transmissions

Before we dive into the causes and fixes for the P0734 error code, let’s take a moment to understand gear ratios in automatic transmissions. Gear ratios determine the relationship between the rotational speed of the engine and the rotational speed of the wheels. Each gear has a specific ratio, which allows the engine to operate efficiently at different speeds. When the transmission shifts gears incorrectly, it can lead to problems like the P0734 error code.

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Causes of P0734 Error Code

Worn or Damaged Transmission Components:

  1. One of the common causes of the P0734 error code is worn or damaged transmission components. Over time, the gears, clutches, or bands within the transmission can wear out or become damaged, leading to incorrect gear ratios.

Faulty Transmission Control Module (TCM):

  1. The TCM is responsible for controlling the shifting of gears in an automatic transmission. If the TCM malfunctions or develops a fault, it can result in incorrect gear ratios and trigger the P0734 error code.

Low Transmission Fluid Level:

  1. Insufficient transmission fluid can also cause the P0734 error code. Low fluid levels can lead to inadequate lubrication and hydraulic pressure, affecting the transmission’s ability to shift gears accurately.

Diagnosing the P0734 Error Code

To effectively fix the P0734 error code, it’s crucial to diagnose the root cause accurately. Here are some diagnostic steps you can take:

Using a Diagnostic Scanner:

  1. Connect a diagnostic scanner to your vehicle’s onboard computer system to retrieve the error codes. The scanner will provide specific information about the error code P0734 and any other related codes, helping you pinpoint the issue.

Checking Transmission Fluid Level and Condition:

  1. Ensure that your vehicle has enough transmission fluid and that it’s in good condition. Low fluid levels or dirty fluid can contribute to gear ratio problems. Refer to your vehicle’s manual for the correct procedure to check the fluid level and condition.

Inspecting Transmission Components:

  1. If the transmission fluid level and condition are satisfactory, you may need to inspect the transmission components. This step requires mechanical expertise and may involve removing the transmission pan to inspect the gears, clutches, and bands for signs of wear or damage.

Fixing the P0734 Error Code

Once you have identified the cause of the P0734 error code, you can proceed with the appropriate fix. Here are some potential solutions:

Replacing Worn or Damaged Transmission Components:

  1. If worn or damaged transmission components are causing the error code, you’ll need to replace them. This task requires technical knowledge and expertise, so it’s recommended to consult a professional mechanic or a specialized transmission shop.

Repairing or Replacing the Transmission Control Module:

  1. If the TCM is at fault, it may need to be repaired or replaced. The TCM is a complex electronic component, and it’s advisable to seek the assistance of a qualified mechanic or an auto repair shop for this task.

Adding or Replacing Transmission Fluid:

  1. In cases where the error code is triggered by low transmission fluid levels, adding or replacing the fluid may resolve the issue. Refer to your vehicle’s manual for the correct type and quantity of transmission fluid to use.

Tips for Preventing P0734 Error Code

Prevention is always better than cure. To minimize the chances of encountering the P0734 error code or any other transmission issues, consider the following tips:

Regular Transmission Maintenance:

  1. Schedule regular maintenance for your vehicle’s transmission. This includes fluid changes, filter replacements, and inspections as recommended by the manufacturer.

Checking Fluid Levels and Condition:

  1. Regularly check the transmission fluid level and condition. If you notice any signs of leakage or discoloration, have it inspected and addressed promptly.

Promptly Addressing Any Transmission Issues:

  1. If you experience any unusual symptoms, such as rough shifting, slipping gears, or strange noises coming from the transmission, address them promptly. Ignoring such symptoms can lead to more significant problems down the road.


The P0734 error code indicating a “Gear 3 Incorrect Ratio” issue can be a cause for concern, but with the right knowledge and steps, it can be resolved effectively. By understanding the causes, diagnosing the problem accurately, and implementing the appropriate fixes, you can restore your vehicle’s transmission to optimal performance. Remember to prioritize regular maintenance and address any transmission issues promptly to avoid future problems.


1. Can I fix the P0734 error code myself?

Fixing the P0734 error code requires technical knowledge and expertise, especially when dealing with transmission components or the transmission control module. It’s recommended to consult a professional mechanic or a specialized transmission shop for accurate diagnosis and repairs.

2. How much does it cost to fix the P0734 error code?

The cost of fixing the P0734 error code can vary depending on the specific cause and the extent of the repairs needed. Replacing transmission components or the transmission control module can be costly. It’s best to obtain quotes from reputable mechanics or transmission specialists to get an accurate estimate.

3. Is the P0734 error code dangerous to drive with?

Continuing to drive with the P0734 error code can potentially cause further damage to your vehicle’s transmission. It’s advisable to address the issue promptly to avoid costly repairs or complete transmission failure.