I have a 2008 Chevy avalanche V8 automatic trouble code p 0 1 2 1 throttle position sensor circuit a faulty reading where's the sensor located and how do I check it

What is the DTC - diagnostic trouble code ? No code tells you a part is bad . Diagnostic testing procedures are given for each code the vehicle can set . Your vehicle can set numerous code's for the electronic throttle control an not one of them tell's you out right to replace the throttle body or the APP sensors . Looking at factory service repair info for the code an doing diagnostic testing befor replacing any parts should be done.

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:
• Accelerator pedal position sensing
• Throttle positioning to meet driver and engine demands
• Throttle position sensing
• Internal diagnostics
• Cruise control functions
• Manage TAC electrical power consumption
The TAC system components include the following:
• The accelerator pedal position (APP) sensors
• The throttle body assembly
• The throttle actuator control module
• The powertrain control module (PCM)

Accelerator Pedal Position (APP) Sensor
The accelerator pedal assembly contains 2 individual APP sensors within the assembly. The accelerator pedal position (APP) sensors 1 and 2 potentiometer type sensors each with 3 circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
The APP sensors are used to determine the pedal angle. The control module provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module with signal voltage proportional to pedal movement. APP sensor 1 signal voltage is low at the rest position and increases as the accelerator pedal is applied. APP sensor 2 signal voltage is high at the rest position and decreases as the accelerator is applied.

Throttle Body Assembly
The throttle body assembly consists of the throttle body, the throttle position (TP) sensors, and the throttle actuator motor. The throttle body functions similar to a similar to a conventional throttle body with the following exceptions:
• An electric motor opens and closes the throttle valve.
• The throttle blade is spring loaded in both directions and the default position is slightly open.
• There are 2 individual TP sensors within the throttle body assembly.
The TP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
The TP sensors are used to determine the throttle plate angle. The control module provides each TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensors then provide the control module with signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens.

Your best bet , take it to a qualified repair shop.

At the throttle pedal.

Throttle position sensor 1 Circuit Low Voltage
possible causes
faulty throttle position sensor
open or short in circuit
Faulty connection at sensor

- Faulty Throttle Position Sensor (TPS)
- Throttle Position Sensor (TPS) harness is open or shorted
- Throttle Position Sensor (TPS) circuit poor electrical connection
- Faulty Powertrain Control Module (PCM)
- Faulty Mass Air Flow (MAF) sensor
- Faulty Manifold Absolute Pressure (MAP) sensor

first code it's P0320 Possible causes
- Faulty Ignition/Distributor engine speed sensor
- Faulty Crankshaft Position sensor
- Ignition/Distributor engine speed sensor harness is open or shorted
- Ignition/Distributor engine speed sensor circuit poor electrical connection
- Low battery charge
- Faulty Engine Control Module (ECM)


Read more: http://engine-codes.com/p0320_ford.html#ixzz3DcwddSlp
2- P0750 Possible causes
- Low transmission fluid level
- Dirty transmission fluid
- Faulty shift solenoid 1 valve
- Shift solenoid 1 valve harness or connectors
- Shift solenoid 1 valve circuit is open or shorted


Read more: http://engine-codes.com/p0750_ford.html#ixzz3DcwoXS73
3- P0120 Possible causes
- Faulty Throttle Position Sensor
- Throttle Position Sensor circuit is open or shorted
- Throttle Position Sensor poor electrical connection


Read more: http://engine-codes.com/p0120.html#ixzz3Dcx3VCPs
4- P0220 Possible causes
- Throttle Position Sensor (TPS) harness is open or shorted
- Throttle Position Sensor (TPS) circuit poor electrical connection
- Faulty Throttle Position Sensor (TPS)
- Fault Electric Throttle Control Actuator (or Throttle Body Motor)
- Accelerator Pedal Position Sensor (APP)


Read more: http://engine-codes.com/p0220.html#ixzz3DcxGUMl4

Code p2120 is accelerator pedal position sensor APP sensor 1 circuit apparently this is known as the reduced engine power syndrome and is quite common on the avalanche. There is no mechanical linkage from gas pedal to throttle body and it is quite common for the throttle position sensor located on throttle body to mess up and throw this code and also for one of the wires to the throttle position sensor to get hot become brittle and sometimes break. I would start there

- Faulty throttle position sensor
- Throttle position sensor harness is open or shorted
- Throttle position sensor circuit poor electrical connection
- Faulty Powertrain Control Module (PCM)

The throttle position sensor is located on the throttle shaft. It would not be in the air cleaner.

Did you test the TPS ( throttle position sensor)?

The automatic transmission uses throttle position sensor to determine position and opening of throttle, and to decide when to shift into gear.
IF throttle position sensor is defective, the car may have problems shifting into one or more gears, and you may also get no error code from OBDII scanner.

The TPS is tested reading volts on the TPS contacts, while someone else from inside the car smoothly press the pedal.

If the TPS is bad, the voltage will not change smoothly, but there will be gaps and peaks in voltage.


If the TPS is ok, then the next step will be checking the transmission shift solenoid pack located in the valve body. This are tested measuring Ohms on solenoids, and cheching if they get powered. This is unlikely the problem, as you would get a P0700 code from TCM.

Finally the TCM (transaxle control module) may be faulty. This may also return no code, as the TCM will think it is doing its job. This fault is also rather uncommon, and can be tested reading voltages on TCM connectors to TPS.

At a glance, from your broad description, you have a faulty TPS.

The check engine light usually comes on when there is a faulty sensor. or circuit. Sounds like you may have a faulty throttle position sensor. It would be best to have engine codes read to pinpoint exact problem area. Many part stores do this for free.