Error Code P0730 is described as Incorrect Gear Ratio. This means the automatic transmission is experiencing a problem, which is usually caused by dirty transmission fluid or problems with shift solenoids.

This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those vehicles made since 1996 up to present. Specifications on the definition, troubleshooting, and repairs of course, vary from one make and/or model to another.


Modern vehicles that come equipped with automatic transmission or tranaxles use a torque converter between the engine and transmission to improve the torque output of the engine and drive the rear wheels. The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes), controls automatic transmission by using multiple gear ratio and increase the vehicle speed to maximize the engine’s power output. Newer vehicle models are equipped with more than four gear ratios for fuel efficiency. The PCM decides when to shift up or down between gears, based on the vehicle speed vs. throttle position. It does so by using the input coming from various sensors to verify the correct operation of the transmission and all its components.

Thus, Error Code P0730 happens in automatic transmission when there is a problem on the shifting or driving to any gear. As a generic trouble code, P0730 also doesn’t pinpoint to any gear ratio failure.

Other related codes include:

Error codes P0729, P0731, P0732, P0733, P0734, P0735 and P0736.

If there are other transmission code problems, they should be fixed first before fixing the incorrect fear ratio code.

Common Symptoms

As with other error codes P0730 triggers the Check Engine light. Common symptoms of this error code may include the following:

  • Delayed shifting or vehicle not shifting into the right gear
  • Slipping transmission
  • Decrease in fuel efficiency

Possible Causes

Error Code P0730 can be caused by multiple factors, such as:

  • Insufficient or dirty transmission fluid
  • Clogged fluid filter or worn pump
  • Solenoid, torque converter clutch or internal blockage
  • Internal blockage in transmission main control
  • Mechanical failure inside transmission
  • Faulty shift wirings or solenoids
  • Faulty transmission control module
  • Defective torque converter clutch

How to Check

Before starting the diagnosis, mechanics would first check the transmission fluid’s level and quality. Old and dirty fluid must be replaced.

To diagnose this error code, technicians use their OBD-II scanner to view real-time information. To codes will then be cleared and the vehicle will be taken for a test drive. If the code comes back, then the problem is really caused by an actual failure in the transmission.

Depending on the severity of the problem, technicians may perform a torque converter stall speed test to determine whether the stall speed of the engine is within the factory specifications or not. The engine must be able to match the readings from the transmission sensor.

How to Fix

Depending on the result of the diagnosis, the repairs for this error code are as follows:

  • Check all electrical connections and wires that connects the sensors to the transmission control module
  • Repair or replace damaged or corroded wires in and around the transmission control module
  • If transmission fluid and wiring are both in good shape, transmission components must be checked for issues and repaired, or replaced if necessary
  • If there are problems with the shift solenoids, pump, or torque converter, the transmission must be removed for proper repairs of these components
  • After conducting the necessary repairs, the transmission must be replaced and checked before being tested to make sure everything works properly without the trouble codes, including P0730.

Low or dirty transmission problem is probably the most common cause of this error code. Thus, by simply replacing the dirty fluid, the issue can be resolved.

The fact that any abnormality in the transmission speed will trigger problems to the gear, the severity of the problem can vary. In severe cases, the problem could trigger major transmission issue, rendering the vehicle unable to change gear. However, it could also be accompanied by other specific trouble codes.

Because of the complexity of the transmission problem, it is always best to have this code diagnosed and repaired by a qualified technician as soon as possible.