P0730 Code: Incorrect Gear Ratio

The engine code P0730 indicates your car’s powertrain control module (or transmission control module) has detected an issue with the transmission’s performance. What causes this trouble code and how do you address it? This short guide will help you answer these questions and more.

What Does the P0730 Code Mean?

Diagnostic Trouble Code (DTC) P0730 stands for “Incorrect Gear Ratio” or “Transmission Control System Malfunction.” Note that the definition of this code will vary depending on the vehicle’s make and model.

Vehicles with an automatic transmission are equipped with a torque converter that’s located between the engine and the transmission. This mechanism multiplies the engine torque and transfers this torque to the transmission. The torque converter also acts as a clutch that prevents the vehicle from stalling, especially when the vehicle is in gear or idling.

The vehicle’s computer or the powertrain control module (PCM) controls the automatic transmission by using planetary gearsets that create multiple gear ratios. The PCM uses information like vehicle speed and throttle position to decide when to shift up or down between gears. The PCM also uses the input from various sensors to verify that the transmission and its components are working properly.

The diagnostic trouble code (DTC) P0730 is set when the automatic transmission encounters a problem with one or more gear ranges, although it does not point toward a particular gear ratio failure. When this code appears, it means that the PCM detects a greater RPM difference between the rotational speed of the input RPM and the transmission output of the RPM sensor. In other words, this code often indicates that the transmission is slipping. This can occur while the driver is shifting or going at steady speeds in the same gear.

If you want to fix P0730 yourself, you can gather more technical information that can help you solve the issue in our discussion about OBD codes and gear ratios.

What are the Possible Causes of the P0730 Code?

Like most OBD-II codes, there are a handful of possible reasons why the engine P0730 is set. Below are just some of the possible causes for this code:

• A mechanical failure inside the transmission
• Defective shift solenoids
• Dirty transmission fluid that restricts the hydraulic passages
• A low transmission fluid level
• Clogged fluid filter or worn pump
• Defective valve body
• Circuit problems, such as damaged wiring and poor connections
• An issue with the PCM or TCM, such as software in need of an update
• Defective engine sensors causing transmission performance problems (rare)

What are the Common Symptoms of the P730 Code?

Below is a list of the most common symptoms of the P730 code:

• Check engine light illuminates
• Vehicle not shifting properly
• Decreased fuel economy
• Vehicle may neutralize
• In some cases, there may be performance problems:
  – Dying when coming to a stop after driving on the freeway
  – Misfire-like symptoms

How to Diagnose the P0730 Code

Proper diagnosis for any OBD-II code is important, and the P0730 code is no different. There are a lot of possible causes per code, and so diagnosis might pose a challenge. Below are some video resources to give you additional information and some tips on how to diagnose the OBD code P0730:

How to Fix the P0730 Code

As mentioned above, proper diagnosis is important in order to fix the P0730 code. Resources like repair guides, repair databases, and video resources can help the average DIYer with P0730 repair. However, if you’re not confident in your repair knowledge and abilities, you can have your trusted mechanic do the job for you.

Other Notes About P0730

The OBD-II code P0730 is related to other codes such as P0729, P0731, P0732, P0733, P0734, P0735, and P0736.

It must be noted that if other transmission codes register in your vehicle’s memory, they should be addressed first before the P0730.

The P0730 is an OBD-II code that needs to be addressed immediately and requires specialized knowledge and skill in order to be fixed properly.

Products Mentioned in this Guide

Transmission Control Module Torque Converter Valve Body Engine Control Module