Reduced engine power light come on.would barely go what is cause an is it an easy fix 2005 Chevy pickup v8 4 door

Jerry, Drive to a good shop. So many things can cause reduced power light unfortunately. The first step would be to get the truck hooked up to a scanner/computer and have the computer scanned for trouble codes. One thing that you could try is to drain the water from the water separator that is mounted on the frame under drivers front door. If the PCM picks up on water, power is reduced until water is removed/drained. It could be an exhaust sensor that is reading faulty. Unfortunately from here its impossible to tell you exactly what the fault is because there are just so many engine sensor inputs that could cause your problem. Check the attached links, forums,instruction and guides, Good luck
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May 27, 2014 - 10 posts - ‎5 authors
OK, many things can cause a reduced engine power message, ... as a regen message and no, idling long enough to fix a wheel WILL NOT plug it up. ... I have a monitor onmy truck that I can watch the accumulated soot grams ...

Engine power reduced can be caused by a number of different issues. Is the check engine light on and have you had codes read?

Let me know.

Not a catalytic converter problem ! All the light's being on is a warning to the driver to take their vehicle to the dealer , not to be inquisitive an try to fix on their own . Complex electronic's , computer , software etc....
ENGINE POWER REDUCED has to do with electronically controlled throttle . Your best bet ,take your vehicle to a qualified repair shop an have diagnostic's run . DTC'S - diagnostic trouble codes stored .
Electronic Throttle Control System Diagnosis Diagnostic Quick Tips Snap on...
Drive by Wire Function and Diagnostics by Wells

The check engine light being on now is a different problem , Have DTC'S - diagnostic trouble codes checked ,will have something to do with electronic throttle control . That is what reduced engine power is about . It's in a reduced power mode.
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.

Do you know what electronic throttle control is ?
--------------------------------------------------------------------------------
Throttle Actuator Control (TAC) System Description

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)

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

why does the reduced power light come on , then the truck stalls. If you pull over and shut down the engine and wait a 30 secounds the truck will restart and run fine until the next time you start the truck. The truck has 48k miles

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

disconecting the battery should reset the pcm. but you will need to find out what caused the problems.

That is a hard problem to pin point without knowing what codes the computer has stored. It can be any number or sensors or engine problems.

You can go to most auto parts stores and they will pull the codes for you for free.

Its a Mapp sensor super easy fix only like a $30 part