Have a pontiac g5 car with engine code of P0121, bad throttle position sensor. how hard are they to fix and how much does a new sensor cost?

code p 0121 refers to throttle position (TP) sensor A/accelerator pedal position (APP) sensor A--range/ performance problem===causes ---accelerator cable adjustment--TP/APP sensor ---wiring

P0121 HYUNDAI - Throttle/Pedal Position Sensor/Switch 'A' Circuit Range/Performance

Possible causes - Faulty throttle position sensor - Throttle position sensor harness is open or shorted - Throttle position sensor circuit poor electrical connection - Faulty Engine Control Module (ECM) What does this mean? When is the code detected? Malfunction is detected when an excessively low or high voltage from the sensor is sent to ECM. Possible symptoms - Engine Light ON (or Service Engine Soon Warning Light) P0121 Hyundai Description The throttle position sensor (TPS) responds to the accelerator pedal movement. This sensor is a kind of potentiometer which transforms the throttle position into output voltage, and emits the voltage signal to the Engine Control Module (ECM). In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM. Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor. This sensor controls engine operation such as fuel cut. On the other hand, the Wide open and closed throttle position switch, which is built into the throttle position sensor unit, is not used for engine control.

P0120 Throttle/Pedal Position Sensor/Switch A -Circuit Malfunction
P0121 Throttle/Pedal Position Sensor/Switch A -Circuit Range/Performance Problem
P0122 Throttle/Pedal Position Sensor/Switch A -Circuit Low Input

,try changing the throttle pedal switch/mechanism on the floor in the cabin

P0121
Throttle Position Sensor/Switch A Circuit Range/
Performance Problem. P1120 Throttle position sensor out of range
P1121. clean throttle body out good, this may fix problem. if not replace or adjust throttle position sensor. Good-Day!

Does your 2.2 have one?

P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance Problem

The Throttle position sensor is a potentiometer that measures the amount of throttle opening. As the throttle is opened, the reading (measured in volts) goes up. The powertrain control module (PCM) supplies a 5 Volt reference signal to the throttle position sensor (TPS) and usually a ground also. A general measurement is: at idle = .5 Volts; full throttle = 4.5 Volts. If the PCM detects that the throttle angle is greater or less than it should be for a specific RPM, it will set this code.

Potential Symptoms: Symptoms of a P0121 trouble code could include:
Malfunction Indicator Lamp (MIL) illumination (Check Engine Light or Service Engine Soon light)
Intermittent stumble on acceleration or deceleration
Blows black smoke on acceleration
No start

Causes: A code P0121 may mean that one or more of the following has happened:
TPS has intermittent open or short internally
Harness is rubbing and causing an open or short in the wiring
Bad connection at the TPS
Bad PCM (less likely)
Water or corrosion in connector or sensor

Possible Solutions:
1. If you have access to a scan tool, see what the idle and WOT (wide open throttle) readings are for the TPS. Check if they're close to the specifications mentioned above. If not, then replace the TPS and re-check.
2. Check for an intermittent open or short in the TPS signal. To do that, you can't use a scan tool. You'll need an oscilliscope. The reason is because scan tools take samplings of many different readings over just one or two data lines and can miss an intermittent drop out. Hook up your oscilliscope and watch the signal. It should sweep up and down smoothly with no drop outs or spikes.
3. If no problems were noticed, perform a wiggle test. Do this by wiggling the connector and harness while watching the pattern. Does it drop out? If so, replace TPS and re-check.
4. If you have no TPS signal, check for 5 Volt reference at the connector. If it's present, check the ground circuit for open or shorts.
5. Make sure the signal circuit isn't 12V. It should never have battery voltage. If it does, trace circuit for short to voltage and repair.
6. Look for any water in the connector and replace TPS as necessary.

Other TPS sensor and circuit related DTCs: P0120, P0122, P0123, P0124

both codes refer to the throttle position sensor, the sensor is at the throttle plate, on the side of the throttle body. to test remove the connector to sensor, use a ohms meter to test. put 1 lead to top connection and the other to the bottom one. move throttle and the needles on the ohms meter should move very even, move throttle slow to get a good reading, needle should move without no hesitation, if the test is bad replace tps sensor. if the sensor gets to bad, it can have an effect on transmission shifting. after fixing sensor have the light turned of with an obd2 scanner.

I believe all the Mopar OBDC codes are the same. A list of the 2001 codes were posted on a PT Cruiser site here: 2001 Chrysler codes

Your error says the throttle position sensor and MAP sensor disagree with each other

The OBD II code for P0400 is Exhaust Gas Recirculation Flow Malfunction.
I'm sure the only thing you have left is you may have to replace the EGR valve or check for any leak from the vaccum lines going to to EGR valve.