Check engine light is on, reduced power displayed on dash, code P2122 and code P2127 comes up

DTC P2127: Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage

This is right out of factory service repair manual , don't google stuff may not be accurate.
If you look under the steering wheel at the gas pedal you will see connectors at the Accelerator Pedal . position sensors inside gas pedal .

Circuit/System Description
The throttle actuator control (TAC) system uses two accelerator pedal position (APP) sensors to monitor the accelerator pedal position. The APP sensors 1 and 2 are located within the pedal assembly. Each sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit.
Two processors are also used to monitor the TAC system data. Both processors are located within the engine control module (ECM). Each signal circuit provides both processors with a signal voltage proportional to pedal movement. The processors share and monitor data to verify that the indicated APP calculation is correct.

It's not see wide open throttle like other guy says .

P2127
The ECM detects that APP sensor 2 voltage is less than 0.16 volt for greater than 0.5 second.


Action Taken When the DTC Sets
• DTCs P2120, P2122, P2123, P2125, P2127, P2128, and P2138 are Type A DTCs.
• The ECM commands the TAC system to operate in Reduced Engine Power mode.


Anytime the vehicle goes into reduced engine power mode A/C shuts off - cruise control won't work etc..

Just change the gas pedal assembly .

Switching on the aircon will rob the engine of a handful of horses but most people most of the time won't notice. Could be the problem goes deep.

By 2007 most vehicles were digital computer controlled so it isn't easy to guess what is going on. I think you need a guy with a good scanner who knows how to use it who can gather and interpret live data.

When this light comes on it means the computer control module has detected a fault in the system, it has reduced power to avoid any damage to the engine or transmission. You must now have the computer scanned for fault codes, this is done through the diagnostic connector under the dash see photo below.

check your aps sensor,accelarator position sensor if its bad and make sure all connector and wire from this sensor to ecu is good,.

The pedal position sensor is throwing a code. could be ECM may need to updated

It is the APP sensors , Your vehicle has electronic throttle control . P2122 Throttle Pedal Position Sensor Switch Circuit Low Your best bet would be to take it to a qualified repair shop .

First of all a scan tool is need for this not a code reader, you need to view scan data after you find what code is stored in the PCM. It could have a problem with the powertrain control module, wiring, or the Accelerator Pedal Position (APP) Sensors. Here are a few codes that could set .
DTC P2120: Accelerator Pedal Position (APP) Sensor 1 Circuit

DTC P2122: Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage

DTC P2123: Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage

DTC P2125: Accelerator Pedal Position (APP) Sensor 2 Circuit

DTC P2127: Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage

DTC P2128: Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage

DTC P2138: Accelerator Pedal Position (APP) Sensor 1-2 Correlation

had the same trouble with my '10 impala it turned out to be defective electronic accelerator pedal it is actually a recall for this vehicle and should be a free repair at your dealer.

Hi Rosalee_IM,
The codes your vehicle is storing are for low voltage from your accelerator pedal position sensor and a gross evaporative emission leak. The code P2122 and P2138 are directing you to test the accelerator pedal position circuit and/ or sensor. This is the cause of the reduced power concern you are feeling.The P0455 is telling you there is a large leak in the evaporative emission system. The most common cause for this code is a loose or incorrectly installed gas cap.I hope this helps clarify the concerns you are experiencing. If you'd like more information on how to trouble shoot the problems,drop me a line. Please include the model Impala you have,(LS,LT or LTZ) and the engine size. I will do my best to get back to you as soon as possible.Thanks, Chuck

Your CODE P1276 refer to the Acelerator Pedal Position, Sensor 1 Circuit Range Performance.

Probable cause: Wiring, APP or ECM


GM - P1271 Accelerator Pedal Position Sensor 1-2 Correlation

I also found this... though its for Trailblazers... but may give you a clue:
Reduced Engine Power Message and/or Check Engine Light with any Combination of the following DTCs: P0107 P0112 P0122 P0452 P1120 P1220 P1221 P1271 P1275 P1280 P1481 P1515 P1540 P1633 P1635 P1639 P1682 #PIP3192 - (Oct 18, 2004)

Reduced Engine Power Message and/or Check Engine Light with any Combination of the Following DTCs: P0107 P0112 P0122 P0452 P1120 P1220 P1221 P1271 P1275 P1280 P1481 P1515 P1540 P1633 P1635 P1639 P1682 PCM Repeat.

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Condition/Concern:
Reduced engine power message and/or check engine light with any combination of the following DTCs: P0107 P0112 P0122 P0452 P1120 P1220 P1221 P1271 P1275 P1280 P1481 P1515 P1540 P1633 P1635 P1639 P1682

Recommendation/Instructions:
If the SI diagnostics did not isolate a concern, the following information may be helpful:
- Inspect the main engine wiring harness between the PCM and the generator assembly for a potential short to ground. There is a metal wiring harness retainer in this area that secures the main engine harness. If the harness conduit is mispositioned, some of the wiring may become exposed and chaff on the harness retainer. This may eventually cause the exposed circuit to short to ground.

- Inspect the 3 harnesses that connect to the PCM for potential shorts to ground on the metal PCM mounting bracket, just below the PCM. There are plastic harness retainers on the PCM bracket that secure the harnesses to the PCM bracket. If the harness conduit is mispositioned, some of the wiring may become exposed and chaff on the PCM bracket. This may eventually cause the exposed circuit to short to ground.

- If a chaffed circuit is found in either of the above locations, repair the circuit using the necessary SI procedures. Once the circuit is repaired, tape the area of the affected area of the harness to prevent the wires from becoming exposed in the future and secure the harness using the original harness retainer.

This applies to 04:
- 4.2L 5.3L LL8 LM4 Engine with DTC - P2120 or P2122 or P2123 or P2125 or P2127 or P2128 - kw low MIL pedal power reduced #PI01746 - (Feb 17, 2004)
- 4.2L 5.3L LL8 LM4 Engine with DTC - P2120 or P2122 or P2123 or P2125 or P2127 or P2128.

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

Condition/Concern:
MIL light on. Reduced Power message on DIC. Possibles DTCs P2120 and/or P2122, P2123, P2127, and P2128.

Recommendation/Instructions:
The APP harness is clipped to the accelerator pedal bracket. The harness may chaff on the upper portion of the accelerator pedal causing a short to ground. Verify the harness is not chaffing on the accelerator pedal. After repairing the short, reposition the harness to ensure no contact between the harness and the accelerator pedal.

Hope helpes.