What does it mean?
Modern vehicles equipped with automatic transmissions/transaxles use a torque converter between the engine and the transmission to increase engine torque and drive the rear wheels.
This code may appear in vehicles with an automatic transmission when there is a problem shifting into or to a gear; this code is generic and does not specifically point to a particular gear ratio failure. The computer-controlled automatic transmission uses multiple gears to increase vehicle speed while maximizing engine power output. Newer vehicles may have more than four gears to improve fuel economy. The computer determines when to upshift or downshift between gears based on throttle position relative to vehicle speed.
The Engine Control Module (ECM), Powertrain Control Module (PCM), or Transmission Control Module (TCM) uses inputs from various sensors to verify the proper operation of the transmission and its components. Engine speed is often calculated relative to the transmission speed sensor to determine the gear ratio and torque converter slippage. If the calculation does not match the desired value, a diagnostic trouble code is set and the Check Engine light is illuminated. Incorrect ratio codes typically require advanced mechanical capability 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 issues before proceeding with an incorrect gear ratio code.
Symptoms
Symptoms of a P0730 trouble code may include:
- Check Engine light is on (malfunction indicator)
- Delayed shifting or not shifting into the correct gear
- Transmission slipping
- Loss of fuel economy
Potential Causes
Causes of this DTC may include:
- Low or dirty transmission fluid
- Worn pump or clogged fluid filter
- Torque converter clutch, solenoid, or internal lockup
- Mechanical failure inside the transmission
- Internal blockage inside the main transmission control
- Faulty shift solenoids or wiring
- Faulty transmission control module
Diagnostic and Repair Steps
Always ensure to check the fluid level and condition before proceeding with diagnosis. Incorrect fluid level or dirty fluid can cause shifting problems affecting multiple gears.
The torque converter stall speed test can be performed according to manufacturer guidelines. Consult your service manual before proceeding with the test. If the engine stall speed does not meet factory specifications, there may be a problem with the torque converter or an internal transmission issue. This could be the cause if multiple incorrect ratio codes are displayed in addition to P0730.
The torque converter clutch, internal clutches, and bands are typically controlled by a solenoid using fluid pressure. If there is an electrical problem with the solenoid, a specific code for that fault should also be displayed. Fix the electrical issue before proceeding. A blocked fluid passage inside the transmission can also cause the P0730 code to be set. If there are multiple incorrect ratio codes but the transmission operates as expected, there might be a mechanical problem with the torque converter, main transmission control, or pressure issues.
It may be necessary to use an advanced diagnostic scan tool to determine which gear is being commanded by the transmission and to determine if the engine speed matches the calculated output speed from the transmission sensor.
In-depth 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.