P0730 OBD-II Trouble Code: Incorrect Gear Ratio

check engine light

P0730 code definition

The P0730 code identifies a problem within an automatic transmission. The P0730 code is often associated with the P0729, P0731, P0732, P0733, P0734, P0735, and P0736 trouble codes.

What the P0730 code means

P0730 is the OBD-II generic code for an incorrect gear ratio detected in an automatic transmission. The ratio of a combination of engine speed and throttle position and the speed of the transmission is used to determine what gear the transmission will use when driving. If there is a problem with any gear within the transmission, then the P0730 code will appear once this ratio is calculated from the sensor data in the transmission.

What causes the P0730 code?

The incorrect gear ratio code may have several causes:

  • Bad or dirty fluid in the transmission
  • Low fluid in the transmission
  • Broken mechanical components within transmission
  • Internal blockage in fluid lines
  • Bad transmission control module
  • Problem with the torque converter clutch
  • Problem with the shift solenoids

What are the symptoms of the P0730 code?

Eventually, the P0730 code will cause the Check Engine Light to illuminate on the dashboard. Along with this indicator, there may also be slipping within the transmission and poor overall transmission performance. The transmission may stay in a low gear for too long, or stay in a high gear until the engine stalls. Fuel economy may worsen as well.

How does a mechanic diagnose the P0730 code?

Prior to further diagnostic tests, the fluid in the transmission should be checked for quality, and the level of fluid should be noted. Old or dirty fluid should be replaced.

The P0730 code is diagnosed with an OBD-II scanner in the hands of a qualified technician. This will provide them with the necessary information from the engine that they can view in real-time. The code will be cleared and the mechanic will take the car for a test drive. If the code comes back, then the code was caused by an actual problem in the transmission.

Depending on the severity of the issue, the technician may perform a torque converter stall speed test to determine if the engine stall speed is within factory specifications. The engine speed must match the readings from the transmission sensor.

Common mistakes when diagnosing the P0730 code

The biggest problem that pops up when diagnosing the P0730 trouble code is that the symptoms may all be stemming from low or dirty transmission fluid. Topping off or replacing this fluid may solve all of the issues in the transmission triggering the trouble code.

How serious is the P0730 code?

The severity of P0730 code depends mostly on the application. In some cases, minor issues can trigger the code, due to the fact that any abnormality in the transmission speed will trigger it in any gear. It could also be triggered when there is a major problem with the transmission, rendering it unable to change gear, though it would likely be accompanied by other, more specific trouble codes.

When the P0730 code appears it is best to have it diagnose by a qualified technician. In many cases, the problem goes away as soon as the code is reset once, especially in cases where the Check Engine light appeared immediately upon startup.

What repairs can fix the P0730 code?

The most common repairs to address the P0730 code are as follows:

  • Inspect electrical connections and wires connecting sensors to the transmission control module.
  • Repair or replace any corroded or damaged wires in and around the transmission control module.
  • If the transmission fluid and wiring is all in working condition, then components in the transmission itself may need to be repaired or replaced.
  • If there is a problem with the pump, shift solenoids, or torque converter, then the transmission will have to be removed for the repairs to take place.
  • Once the necessary repairs are made, the transmission must be replaced and inspected before being tested to ensure that it works without any trouble codes, including the P0730 code.

Additional comments for consideration regarding the P0730 code

If the Check Engine Light comes on because of the P0730 trouble code right when the vehicle starts, then it can probably be fixed by simply resetting the code. Small problems with the wiring, common in aging vehicles, can easily trigger certain trouble codes without the presence of a serious problem. When the P0730 code appears, it often does so alongside several other error codes.

Need help with a P0730 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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