2006 dodge grand caravan 3.3 transmission won't shift out of low gear could this be caused by the transmission relay?

If you own a Chrysler, Dodge, or Plymouth vehicle and discover that the transmission will shift from first to second gear but will not shift out of second gear, your vehicle has locked itself into “limp-in” mode. That means the computer has detected a problem with the transmission and will not allow it to shift out of second gear in order to prevent further damage to the transmission. The vehicle may shift properly after a restart, only to lock back into limp-in mode again which won’t allow it to shift out of second gear. To diagnose, follow these instructions. First, check for transmission related trouble codes in the computer. You may find any of the following codes: P0700, P0715, P0720, P0731, P0732, P0733, or P0734. You can read any of these codes with an inexpensive code reader. But you’ll need a scan tool with some live data capabilities to continue the diagnosis. Quit whining, they’re not that expensive and if you want to fix your own vehicle you have to have the right tools The problem is usually caused because the Transmission Control Module (TCM) cannot determine the input or output shaft speed. To the TCM that can mean one of two things; either the sensor is bad, or there’s an internal problem with the transmission. input shaft sensor, turbine sensor, transmission won't shift out of second gearoutput shaft sensor, transmission won't shift out of second gear Connect your scan tool and start the engine, leaving the transmission in PARK. The engine RPM should closely match the Input Shaft (also called the Turbine shaft). This should be logical; the engine turns the torque converter at the same speed as the engine and the Input Shaft sensor is clocking the speed of the torque converter. If that checks out, drive the vehicle slowly and watch the speed of the Output Shaft Sensor. It should rise slowly, corresponding to your vehicle speed. If either sensor is off or completely dead, replace it with a factory sensor. You read that right, a genuine Chrysler part. Trust me on this, you’ll regret buying an aftermarket sensor. I’ve seen too many people put those in and continue to have the same problem only to find the aftermarket sensor isn’t accurate. You can also test the sensor with a digital ohm meter. It should read about 800 ohms. Also, verify that the wiring harness and connectors are in good shape.

Thank You, We have a P0750 code shift solenoid. We are going to transmission mechanic. Grandparog

Put trans in and won't start. Run before we took it out