2008 Silverado replaced peddle sensor and throttle position sensor still reduced engine power on

Your engine has an electronic throttle body. They don't use an idle air control valve. They control idle by cracking open the throttle plate electronically. If you have idle problems, chances are you've got carbon buildup around the throttle plate. Here's how to clean it. http://ricksfreeautorepairadvice.com/clean-an-electronic-throttle-body

How many miles does it have on the odometer ? The reduce engine power has to do with the ETC electronic throttle control . May have TPS - throttle position sensor problem or the APP sensor . 04 Silverado REDUCED ENGINE POWER Case Study Part 1

2003 Silverado 2500HD REDUCED ENGINE POWER - Discussion on Topix

www.topix.com > Top Stories
Dec 28, 2009 - 20 posts - ‎12 authors I have replaced the throttle body, had the wires re-connected and .... The gauges all went wild and reduced engine power displayed on the dash. I looked it .... The truck just went to idle for no reason and it keeps happening. 2003 Chevy Trailblazer-CHECK ENGINE LIGHT AND ...
Dec 23, 2011
Reduced Engine Power message
Jul 29, 2008
2003 Chevrolet Silverado - Reduced Engine Power
Nov 3, 2007
Trailblazer - Reducted Engine Power
Aug 3, 2006
More results from www.topix.com

Reduced Engine Power Message Displayed on GM Vehicles

www.underhoodservice.com/tech-tip-reduced-engine-power-message-dis...
Dec 10, 2012 - Tech Tip: Reduced Engine Power Message Displayed on GM Vehicles ... Model year 2008-'10 vehicles must have the engine control module (ECM) reprogrammed ... Do not drop the electronic throttle control components.

The automotive trouble code P2138 throttle/pedal position sensor/switch D/E voltage correlation refers to a problem related to the throttle's ability to open and close properly. Replace (suggest) the sensor (black object) on the throttle body.

My 2008 SRX also had this problem, at first I would turn the engine off and that would fix the problem, but then both the check engine light and the reduce engine power light would come right back on. I brought it to my local mechanic and the code that came up was for the timing chain or the crank shaft. They checked with cadillac and they had problems with timing chain so that was replaced. It was fine for a few days and is now doing the same exact thing. Can anyone help?

APP 1 and APP 2,Throttle position correllation. Whenever you get a reduced power,It will always be related to the throttle actuator, or APP (accelerated pedal position).There is a disagreement between both position sensor, or the TPS itself.

DTC P0120 P0220 P1516 P2135 these should be the problem codes.
2003-2006 Chevrolet Avalanche, Corvette, Express, Monte Carlo, Silverado, SSR, Suburban, Tahoe, Trailblazer. for reduced engine power. p0120 is throttle position sensor, ( tps ). p0220 is relates to tps, p1516 tps is out of range. p2135 is a throttle body code, the throttle body needs replaced. but before you do it replace tps first to see if it takes care of the other codes. have a good day !!

it sounds me like the app sensor is bad, i dont think tps will cause reduced engine pewer, but app sensor will . u have to replace the trottle body to fix the app sensors uder the hood.
replace the accelleator pedal to fix the app sensors n the cab.
there is a ground wire in the big wire loom behind the intake if u loose ground ull get that reduced power issue i replaced throttle body and accellerator pedle n had the same reduced power few minutes after test drive came back cleared the codes then found a hit on idenafix for ground in the big wire loom ground went to fire wall and was bearly hanging on broke when i touched it fixed it witha crimp on fitting, havent had the code set since

Your going to have to get the Sierra scanned for the DTC code to why it's setting the ECM to reduce the power. Auto Zone or Parts Source will scan free of charge so you can address the issue. There are a few things that will set the reduce engine power like a faulty throttle peddle position ECT. Keep me posted, be glad to help you get your Sierra running 100% again soon.

The reduced engine power happens because there is a problem with the electronic throttle control . Some people call it drive by wire ! The gas pedal has sensors inside , position sensors , connected electrical to the PCM - engine computer , the throttle body on the engine has a DC electric motor an also has position sensors . These are also connected to the PCM electrical . The PCM reads the position sensors which indicate how much your pressing on the gas pedal . then hopefully it opens the throttle the same amout .

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 includes the following components:
• The accelerator pedal position (APP) sensors
• The throttle body assembly
• The engine control module (ECM)

Reduced Engine Power Mode
When the ECM detects a condition with the TAC system, the ECM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
• Acceleration limiting--The ECM will continue to use the accelerator pedal for throttle control, however, the vehicle acceleration is limited.
• Limited throttle mode--The ECM will continue to use the accelerator pedal for throttle control, however, the maximum throttle opening is limited.
• Throttle default mode--The ECM will turn OFF the throttle actuator motor and the throttle will return to the spring loaded default position.
• Forced idle mode--The ECM will perform the following actions:
- Limit engine speed to idle by positioning the throttle position, or by controlling the fuel and spark if the throttle is turned OFF
- Ignore the accelerator pedal input
• Engine shutdown mode--The ECM will disable fuel and de-energize the throttle actuator.

GM Electronic Throttle Body Circuit Descriptions And Testing Tips

Tons of videos on youtube for these systems , there can be a variety problems , from wiring , worn out sensors , the DC motor , computer etc....