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P0730 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

DTC P0730, Incorrect Gear Ratio; This indicates a problem with the automatic transmission, generally caused by filthy transmission fluid or shift solenoids.

Meaning

P0730 is the OBD-II (onboard diagnostic-II) generic code for an improper gear ratio in an automatic gearbox. This code is general and can be found in vehicles with an automatic gearbox when there is difficulty changing into or driving into any gear.

Vehicles fitted with an automatic transmission or transaxles (a transaxle is a single mechanical device that integrates the operations of an automobile’s transmission, axle, and differential into one integrated unit. Manual and automated versions are available) have become more common in recent years. Trying to enhance torque output, a torque converter is attached between the engine and transmission to drive the back wheels. 

An automated gearbox with computer-controlled settings that incorporates several gear ratios improves vehicle speed while also maximizing the engine’s power output. Additionally, newer cars may have gear ratios ranging from four to more than eight to achieve better fuel economy. The computer automatically shifts gears based on whether the throttle is at a higher or lower position when compared to vehicle speed.

The automatic transmission module in vehicles selects the most suitable gear ratio for the vehicle speed. The auto transmission module controls the engine’s torque and power characteristics to match the driver’s intended speed. 

The P0730 error will be set if the Transmission Control Module (TCM) notices a discrepancy in the rotational speed (RPM) between the transmission output Revolution Per Minute (RPM) sensor and the input RPM sensor. Shifting between gears or driving at a constant pace in a specific gear might cause this issue.

Causes

Listed below are some possible causes of the formation of the onboard diagnostic II (OBDII) diagnostic issue number P0730;

  • Transmission fluid is contaminated 
  • Filter or pump has become clogged or worn out
  • Internal obstruction or blockage in solenoid in the torque converter
  • Internal blockage in the main transmission control 
  • Mechanical damage inside transmission
  • Faulty shift wirings or solenoids
  • Faulty transmission control module
  • Defective torque converter clutch

Symptoms

Listed below are some possible symptoms associated with the P0730 error code. However, the most frequent indications and symptoms linked with P0730 is a decrease of the RPM limiter.

  • This code will cause the Check Engine Light (CEL) on the dashboard to light.
  • The signs of a misfire may be present
  • Transmission slipping/high/low, gears are not moving in a proper manner
  • When travelling on the highway, the vehicle comes to a complete halt.
  • Vehicle shifts very slowly or does not shift into the appropriate gear at all.
  • Too long in a low gear or too long in a high ratio might cause the engine to shut down.
  • There is a reduction in fuel economy.

Diagnosis

To see real-time information and troubleshoot error code P0730, OBD-II scanners are utilized. Upon clearing the codes, a test drive will be performed. If, after a test drive, an error code is still shown, the correction communication has failed.

As per the manufacturer’s guidelines, torque converter stall speed tests can be done. Before performing the test, go through your owner’s handbook. Engine stall speed may not be within original standards if a torque converter or internal gearbox issue is present. When P0730 is shown together with other ratio error codes, this may be the problem. Fluid pressure is frequently used to regulate the torque converter clutch, internal clutches, and bands. The solenoid should also display a fault code if there is an electrical problem.

Inspect the transmission fuse, if it is found to be faulty. Verify that none of them is defective before proceeding.

As a next step, inspect the transmission wire harness and connectors for damage. 

Next, test the Torque Converter Clutch (TCC) solenoid itself and confirm that the Transmission Control Module (TCM) has been instructed to turn it on by sending a signal to the solenoid. This type of diagnostic is a bit more complicated and may require the assistance of a professional. Check the following things while checking the torque convertor clutch.

  • Inspect electrical connections and cables connecting sensors to the transmission control module.
  • Inspect the transmission speed sensor for any broken cables.
  • Check that the transmission fluid is at the correct level and the transmission sensor and solenoid wire are in good operating condition.

Diagnostic Mistakes to Avoid

Misdiagnoses include internal transmission problems and engine misfiring, which are both common errors. Transmission fluid that is filthy or low may be the cause of the symptoms you are experiencing. Replacing or topping up the transmission fluid may fix the transmission problems that are producing the fault code.

How Serious Is This Code?

There is significant variation in the severity of the P0730 code among applications. Minor problems can cause the code to activate since any slowdown in transmission speed causes it to activate in any gear. It may also occur when there is a serious transmission malfunction, such as a blown fuse, which would result in the car not being able to shift gears.

In the event that the P0730 code arises, a technician certified by the manufacturer should diagnose the problem. Most of the time, after the code is reset, the problem disappears, particularly if the Check Engine light comes on at the restart.

What repairs can fix the code?

Depending on the diagnosis, the fixes are as follows:

  • The most prevalent reason for this error code is likely to be a low or filthy transmission. Replace the filthy fluid to remedy the problem.
  • All electrical connections and cables that link the sensors to the transmission control module should be inspected and repaired as necessary.
  • In and around the transmission control module, repair or replace broken or corroded cables with new ones.
  • The transmission's wiring and fluid may still need to be fixed or replaced, even if they are in good shape.
  • If the torque converter, shift solenoids, or pump are malfunctioning, the transmission must be removed.

Related codes

  • P0729
  • P0731
  • P0732
  • P0733
  • P0734
  • P0735
  • P0736

Conclusion

DTC P0730 is a complex error and can cause a serious problem to the vehicle. An expert mechanic with his dedicated tools can fix the issue. Ideally, the code should be diagnosed and corrected by a professional who is fully certified as soon as feasible.

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