Hey galyagornishka, sorry to hear about your car problems.
The transmission’s Input Speed Sensor (ISS) is also know as a Turbine Speed Sensor (TSS) and is located on the outside of the transmission’s case. It determines the rotational speed of the input shaft or torque converter and relays this information to the control unit. Using information from the ISS and the vehicle speed sensor (VSS), the control unit can make adjustments to enable the vehicle to shift smoothly and efficiently. Symptoms include improper shifting, slipping and a lit check engine light.
So from the description you provided, the input speed sensor could definitely be the issue. The cost of labor and parts to replace the sensor should be in the $100-$200 range.
Code P0212 – Injector Circuit Malfunction. There is a problem with the fuel injector. It could be due to an open or shorted harness, a faulty injector or a poor electrical connection.
Symptoms – Engine runs rough/hesitation. Check engine light is on. Engine will be harder to start. Poor power/acceleration.
Solution – Fuel injector cleaner, check the wiring, check/replace the injector. Cost to replace: $70-$80 each plus labor
Code P0234 – Turbocharger/Supercharger ‘A’ Over boost condition. The Turbo Charging system uses a Boost Pressure Sensor sends info to the PCM so it can determine how much boost is being provided. When the sensor data reads above specifications or the Knock Sensors pick up pinging/knocking, P0234 is set.
Symptoms – Engine light on. Engine knocks or pings on acceleration or hesitates or stalls. Engine lacks power since there is no boost from the turbo charger.
Causes – Transmission oil temperature is too high, engine over temperature, knock sensor (KS) failure, faulty boost pressure sensor, faulty boost sensor wiring, ignition misfire exceeds threshold.
My advice is to take your Accent to a reputable transmission shop in the area ASAP. They will be able to provide a more exact diagnosis and give you an estimate for the repairs. Driving around before getting the sensor fixed will be very hard on your transmission and you could do enough damage to require a rebuild/replacement. If the problem is more severe than the sensor or codes and the transmission has to be rebuilt or replaced, expect the cost to increase significantly.