2002 GMC Envoy had Reduced Engine Power light, no accleration possible and code P1516 and P1512.

code p1512 refers to intake manifold runner control stuck closed
replace it or remove it and clean it

On your dash it says REDUCED ENGINE POWER. Clean your throttle body and reset codes. If codes clear you should be fine if not wiggle and pull on wires at connector for throttle body. The grey one is known to break in the pigtail. Resolder and reset light. A dirty throttle body causes lots of problems

Did you also have a "check engine" or "service engine soon" light? If so, did you have a scanner "read" the error code and record what code was set? It sounds like a throttle body problem, but the OBD code will narrow it down.

originally i had coes 1515 and 1516 with a no start condition. i now only have a 1515. i have checked all wiring and all is good. all reference v are correct and i am stuck because i am having no luck finding diag for this. Any help would be much appeciated.

Here is the definition of the code.

Possible causes - Faulty Throttle Actuator Control (TAC) module
- Throttle Actuator Control (TAC) module harness is open or shorted
- Throttle Actuator Control (TAC) module circuit poor electrical connection (loose or broken wires)

P1516 CHEVROLET Description The Throttle Actuator Control (TAC) module contains data which is essential for proper TAC operation. The TAC module continuously test the integrity of this data. When the TAC module is unable to write or read data to and from Random Access Memory (RAM), or the TAC module is unable to correctly read data from the flash memory or and internal TAC module processor fault is detected and the Detected Trouble Code (DTC) is set.
Read more: http://engine-codes.com/p1516_chevrolet.html#ixzz286Gl3cSo

Sounds like your throttle body is sticking. Common problem, the reduced power is just a safe mode. 1st disconnect your battery, then clean your throttle body with throttle body cleaner. When finished, connect the battery back up. Turn off all accessoried and drive around for 20 minutes or so, for the computer to relearn a properly functioning throttle body. Should solve your problem, and if you do it yourself, will cost you around $5 for the can of TB cleaner.

Reduced engine power is just like a safe mode. First things first, clean your throttle body. It's possible the butterfly is sticking. Disconnect the battery, clean your throttle body with throttle body cleaner, must be nice and shiny. When finished, drive around for 20 minutes or so with all accessories off. This will allow the computer to relearn a properly functioning throttle body.

Pt 1 2007 Chevy 2500HD Reduced Engine Power Warning Fault Code P1516...

may have a bad throttle body check for codes if you have a p01516 must of the time it is a throttle body problem

hi, those sound like throttle actuator codes. the throttle body on your vehicle should be an electronically controlled unit without wires to control actual acceration an deceleration. now, there is also an electronic switch called a potentiometer on the gas pedal that transmits signal to the throttle body to tell it what to do. most of the time, the throttle body is what goes bad here. you should also check the wiring to the unit for bad connection by wiggling the wire connector and seeing if the reduced engine power light comes on. if this happens, you will likely have to replace the wiring pigtail and the throttle body. but, in some cases, the gas pedal switch goes bad, and likely what is not allowing the transmission to shift out of park, the pcm may lock out the solenoid controlling the shifter. but, don't just run with that answer, it maybe completely wrong. i have seen more throttle bodies and wiring harnesses go bad than gas pedal switches in those vehicles. but you might want to have a shop diagnose further, it may even be two unrelated problems, or in the powertrain computer itself.