P0730 Incorrect Gear Ratio
OBD-II Trouble Code Technical Description
Incorrect Gear Ratio
This diagnostic trouble code (DTC) is a generic OBD-II powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may vary depending on the model.
What does that mean?
Modern vehicles equipped with automatic transmissions / transaxles use a torque converter between the engine and transmission to increase the engine torque output and drive the rear wheels.
This code can show up in vehicles with an automatic transmission when there is a problem shifting into or driving into any gear, this code is generic and does not specifically point to any particular gear ratio failure. The computer controlled automatic transmission uses multiple gear ratio’s to increase vehicle speed while maximizing the power output from the engine. Newer vehicles may have more than four gear ratios to improve fuel economy. The computer determines when to shift up or down between gears based on throttle position vs. vehicle speed.
The Engine Control Module (ECM), Powertrain Control Module (PCM) or Transmission Control Module (TCM) uses input from various sensors to verify the correct operation of the transmission and its components. Engine speed is often calculated against the transmission speed sensor to determine gear ratio and torque converter slip. If the calculation does not match the desired value, the Diagnostic Trouble Code is set and the Check Engine Lamp is illuminated. Incorrect ratio codes typically require an advanced mechanical ability and diagnostic tools.
Note: This code is similar to P0729, P0731, P0732, P0733, P0734, P0735 and P0736. If there are other transmission codes, repair those problems first before proceeding with an incorrect gear ratio code.
Symptoms
Symptoms of a P0730 trouble code may include:
Potential Causes
Causes of this DTC may include:
Diagnostic & Repair Steps
Always be sure to check fluid level and condition before proceeding with further diagnosis. Improper fluid level or dirty fluid can cause shifting issues that affect multiple gears.
Torque converter stall speed test can be performed in accordance with manufacturers guidelines. Consult your service manual before proceeding with the test. If the engine stall speed is not within factory specifications, there may be an issue with the torque converter, or an internal transmission problem. This may be the cause if multiple incorrect ratio codes are displayed in addition to the P0730.
The torque converter clutch, internal clutches and bands are usually controlled by a solenoid using fluid pressure. If there is an electrical issue with the solenoid, a code specific to that fault should also be displayed. Correct the electrical issue before proceeding further. Blocked fluid passage inside the transmission can also cause the P0730 to set, if there are multiple incorrect ratio codes but the transmission performs as expected, there could be a mechanical issue with the torque converter, transmission main control, or pressure problems.
It may be necessary to use an advanced diagnostics scan tool to determine which gear is being commanded by the transmission, and to determine if the engine speed matches with the calculated output speed from the transmission sensor.
Advanced knowledge of transmission operation and overhaul is often required to repair this type of malfunction. Consult the factory service manual for vehicle specific diagnostic procedures.
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"Delete Error Code Permanently, Disable DTC Error Code Function for p0730 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p0730 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0730.
