Where is the location of throttle actuator control module on a v6, 2006 gmc envoy? I believe it may be a reason why my vehicle will not crank. I got DTC: P1516 on a code reader. My brake is locked-in. I erased the code and disconnected the battery after reinstalling the battery it cranked. I let it run for ten minutes with no problem, only when I turned the car off I could not get it to crank again. Any ideas before I have it towed? Any advice would be most appreciated, please.

Question edited for funky spelling and punctuation.
Question moved to model category.

Jeff provides a great answer to the issue

• Jeff Armer Jan 02, 2023. Starter relay contacts stuck closed could be a reason .
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  Circuit Description
  Moving the ignition switch to the START position sends a 12 volt signal to the engine control module (ECM)/powertrain control module (PCM) Crank Request circuit. The ECM/PCM verifies that the transmission is in the PARK or NEUTRAL position. With the transmission in Park, voltage flows through the Park/Neutral position switch and feeds the starter relay coil. The ECM/PCM then grounds the control circuit of the starter relay. When the starter relay is energized it allows battery positive voltage to the starter solenoid S terminal. On some vehicles the starter will continue to crank the engine with the key released until it starts or the crank command has timed out to prevent excessive heat build up in the starter circuitry or the ECM/PCM receives an engine run flag.
  

Air temperature and delivery are controlled via small actuators on the heating, ventilation & air conditioning (HVAC) box located behind the dashboard. These actuators operate doors inside the HVAC box in order to channel air through different passages to achieve the desired result. A "blend" door actuator can channel air through the heater core, around the heater core or a mix of these two to achieve the desired temperature. A "mode" door actuator can direct airflow to the ducts that lead to the defrost vent, front vent, floor vent or a mix between. When a vehicle has dual climate control (where driver and passenger sides of the vehicle can have different air temperatures) there can be multiple of actuators of each type which can make diagnosis difficult. The first step would be to retrieve diagnostic trouble codes (DTCs) from the HVAC Control Module using an advanced level scan tool; these codes help determine the location of the issue and if it's an electronic or mechanical failure. Electronic failures would include items such as HVAC control module failure, actuator circuit failure or actuator failure. Mechanical failures would include items such as actuator failure or internal HVAC box door failure. You can read more here: https://www.yourmechanic.com/article/what-components-of-the-heating-and-ac-system-are-most-likely-to-fail

Reduced engine power is a problem with the electronic throttle control . You need to have a scan tool hooked up to read codes stored .

REDUCED ENGINE POWER: Refer to Powertrain Control Module Description in Engine Controls - 4.8L, 5.3L, and 6.0L

Reduced Engine Power Mode
When the PCM detects a problem with the throttle actuator control (TAC) system the PCM enters one of the following Reduced Engine Power Modes:
• Acceleration Limiting--The control module will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
• Limited Throttle Mode--The control module will continue to use the accelerator pedal for throttle control, however the maximum throttle opening is limited.
• Throttle Default Mode--The control module will turn off the throttle actuator.
• Forced Idle Mode--The control module will perform the following actions:
- Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
- Ignore accelerator pedal input.
• Engine Shutdown Mode--The control module will disable fuel and de-energize the throttle actuator.

Check engine light lit ? Any DTC'S - diagnostic trouble code's stored in any module's (computer's ) on the car ? Hooking up a professional type or factory scan tool an checking for code's in all the computers is what should be done . PCM - engine computer , BCM - body control module , TCM - transmission control module . This is how to determine what sensor is causing the problem . Not guessing an just replacing any sensor . Is the vehicle 2WD or 4WD ? More the likely it's a problem with the Throttle Actuator Control (TAC) System. It's stuck in Reduced Engine Power Mode
When the PCM detects a problem with the throttle actuator control (TAC) system the PCM enters one of the following Reduced Engine Power Modes:
• Acceleration Limiting--The control module will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
• Limited Throttle Mode--The control module will continue to use the accelerator pedal for throttle control, however the maximum throttle opening is limited.
• Throttle Default Mode--The control module will turn off the throttle actuator.
• Forced Idle Mode--The control module will perform the following actions:
- Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
- Ignore accelerator pedal input.
• Engine Shutdown Mode--The control module will disable fuel and de-energize the throttle actuator.


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

P1516 = Throttle Actuator Position Performance
P2101 = Throttle Actuator "A" Control Motor Circuit Range/Performance

Both of these codes indicate a problem with your throttle position actuator system. I'm not sure how GMC/Chevy treat this, it's possible that if the PCM/ECM will not allow the engine to start if the throttle actuator is not working properly (it may cause the engine to accelerate rapidly when running). You could try replacing the throttle actuator, but that may not solve the problem if it's a wiring issue. Best to have it checked out by a qualified mechanic.

I am only able to shoot you a guess on this and hopefully it steers you the right direction. I believe your vehicle went into limp mode. This can be from over heating to emission problems to a bad piston. The vehicle does this to protect itself. The cheapest way to diagnose this one is to take it in. Remember, having it diagnosed does not mean you cannot fix it yourself. Just pay the fee and take it home if it is something you want to tackle.

REDUCED POWER
Refer to:
• Powertrain Control Module Description for the 2.8L engine
• Powertrain Control Module Description for the 3.5L engine

Throttle Actuator Control (TAC) System
Throttle Actuator Control (TAC) Overview
The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.
The TAC system components include, but are not limited to the following:
• The accelerator pedal position (APP) sensors
• The throttle body
• The powertrain control module (PCM)
Each of these components interface together to ensure accurate calculations and control of the throttle position.

Accelerator Pedal Position (APP) Sensor
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The APP is 2 individual APP sensors within one housing. There are 2 separate signal, low reference, and 5-volt reference circuits. APP sensor 1 voltage increases as the accelerator pedal is depressed. APP sensor 2 voltage decreases as the accelerator pedal is depressed.
Throttle Body Assembly
The throttle body for the throttle actuator control (TAC) system is similar to a conventional throttle body with several exceptions. One exception being the use of a motor to control the throttle position instead of a mechanical cable. Another exception is the throttle position (TP) sensor. The TP sensor is mounted in the throttle body assembly. The TP sensor is 2 individual TP sensors within the throttle body assembly. Two separate signals, low reference, and 5-volt reference circuits are used to connect the TP sensors and the powertrain control module (PCM). TP sensor 2 signal voltage increases as the throttle opens. TP sensor 1 signal voltage decreases as the throttle opens.

Reduced Engine Power Mode
When the PCM detects a problem with the throttle actuator control (TAC) system the PCM enters one of the following Reduced Engine Power Modes:
• Acceleration Limiting--The control module will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
• Limited Throttle Mode--The control module will continue to use the accelerator pedal for throttle control, however the maximum throttle opening is limited.
• Throttle Default Mode--The control module will turn OFF the throttle actuator.
• Forced Idle Mode--The control module will perform the following actions:
- Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned OFF.
- Ignore accelerator pedal input.
• Engine Shutdown Mode--The control module will disable fuel and de-energize the throttle actuator.

Have you had it checked for DTC'S - diagnostic trouble codes ?

DTC P2176
The commanded throttle position (TP) is compared to the actual TP. Both values should be within a calibrated range of each other. The powertrain control module (PCM) continuously monitors the commanded and actual TPs. If the values are greater than the calibrated range, DTC P2176 sets.
--------------------------------------------------------------------------------
DTC P2138
The accelerator pedal position (APP) sensors 1 and 2 are located within the accelerator pedal assembly. Each sensor has the following circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated.
DTC P2135
The throttle actuator control (TAC) assembly has 2 throttle position (TP) sensors mounted within the assembly. The powertrain control module (PCM) provides individual signal, ground, and 5-volt reference circuits to each sensor. Both sensors operate within a voltage range between 0.35-4.65 volts. When the throttle is opened from 0-100 percent, one sensor signal voltage increases while the other decreases. The signal circuit for TP sensor 1 is referenced to ground, and the signal circuit for TP sensor 2 is pulled up to 5 volts within the PCM.
DTC P2128
DTC P2127
DTC P2125
DTC P2123

Drive by Wire Function and diagnostics by Wells

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

Check the vehicle for DTC'S - diagnostic trouble code's should be the first step in diagnosing this problem . But a tune - up not ! Reduced enging power is caused by a problem with the electronic throttle control . If you are not familiar with this ,your best bet would be to take to a qualified repair shop.
REDUCED ENGINE POWER: Refer to Powertrain Control Module Description in Engine Controls - 4.8L, 5.3L, and 6.0L

Throttle Actuator Control (TAC) Overview
The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.
The TAC system components include, but are not limited to the following:
• The accelerator pedal position (APP) sensors
• The throttle body
• The powertrain control module (PCM)
Each of these components interface together to ensure accurate calculations and control of the throttle position (TP)
Accelerator Pedal Position (APP) Sensor
The APP sensor is mounted on the accelerator pedal assembly. The APP is actually 2 individual APP sensors within 1 housing. There are 2 separate signal, low reference, and 5-volt reference circuits. APP sensor 1 voltage increases as the accelerator pedal is depressed. APP sensor 2 voltage decreases as the accelerator pedal is depressed.

One of these sensors could be sending conflicting data to the PCM - engine computer .

Reduced Engine Power Mode
When the PCM detects a problem with the throttle actuator control (TAC) system the PCM enters one of the following Reduced Engine Power Modes:
• Acceleration Limiting--The control module will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
• Limited Throttle Mode--The control module will continue to use the accelerator pedal for throttle control, however the maximum throttle opening is limited.
• Throttle Default Mode--The control module will turn off the throttle actuator.
• Forced Idle Mode--The control module will perform the following actions:
- Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
- Ignore accelerator pedal input.
• Engine Shutdown Mode--The control module will disable fuel and de-energize the throttle actuator.

Throttle Body Assembly
The throttle body for the throttle actuator control (TAC) system is similar to a conventional throttle body with several exceptions. One exception being the use of a motor to control the throttle position instead of a mechanical cable. Another exception is the throttle position (TP) sensor. The TP sensor is mounted in the throttle body assembly. The TP sensor is 2 individual TP sensors within the throttle body assembly. Two separate signal, low reference, and 5-volt reference circuits are used to connect the TP sensors and the powertrain control module (PCM). TP sensor 2 signal voltage increases as the throttle opens. TP sensor 1 signal voltage decreases as the throttle opens.

It's referring to a problem detected in throttle actuator control module, but if your not experiencing any driveability issues, it may have been set by a low battery condition as well. Are you experiencing any, or has battery gone low that you know of recently?