P0730: Incorrect transmission Gear Ratio

What Does Code P0730 Mean?

This circuit monitors actual transmission gear position by checking the torque converter clutch (TCC) slip ratio calculated by Transmission control module. The Engine Control Module (ECM or PCM) or TCM uses inputs from many different sensors to contol the correct operation of the transmission. Engine speed is often calculated and compared against the transmission output speed sensor to determine the correct gear ratio and torque converter slip rate.

If this value does not match the value the computer expects to see, this DTC is set and the Check engine Light is illuminated. If the actual gear position is higher than that of the position expected by the computer, the slip ratio will be more than normal. The computer determines when to upshift or downshift based on TPS and vehicle speed. Incorrect gear ratio codes usually require a mechanic with good electrical ability and diagnostic tools to diagnose properly.

Code P0730 Symptoms

• Problem shifting into or driving into any gear
• Check engine light

Common Causes of P0730

• Dirty Tansmission fluid
• Resticted filter
• Faulty shift solenoids
• Transmission slipping
• TCC solenoid circuit
• Internal torque converter problem

This code is called a generic code. That means it can relate to any make and model vehicle 1996 year or newer. Vehicle specific diagnosis may be needed.

How is the P0730 detected?

The TCM detects that the transmission is trying to shift into a lower gear than was intended.

How to Diagnose Code P0730

A torque converter stall speed test should be performed. This can be done with a good scanner. If engine stall speed is not within specs, there could be a problem with the torque converter or possible an internal transmission problem. The torque converter clutch, clutch packs and bands are controlled by a solenoids using line fluid pressure. If there is an electrical problem with a shift solenoid, a code for that problem would also be displayed in the scanner stored codes data.

You must repair any electrical issues before proceeding with further diagnosis of this code. Resticted fluid passage inside the transmission can also cause code P0730. If there are several incorrect gear ratio codes but the transmission seems to be shifting normally, there could be a mechanical fault inside the torque converter, transmission valve body, or a fluid pressure problem.

As a final note: Some GM vehicles have a service bulletin for this code. Contact your local dealer with the vehicle VIN nunber and they will be able to give you more information.