Will not go out of low power mode

Hi,

Have you checked the accelerator pedal position sensor? See pic 1. Also, have you checked the throttle position sensor?

The voltage you mention is correct. Here are descriptions of the two things I mentioned. Let me know if they have been replaced as well.

_______________________________

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.

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 power-train control module (PCM). TP sensor 2 signal voltage increases as the throttle opens. TP sensor 1 signal voltage decreases as the throttle opens.

________________________________

Let me know.

Joe

Hi,

Are you referring to the TPS or APP sensor? If the TPS and nothing changes, suspect the APP and vice versa.

Let me know exactly what you did and results.

Take care and happy new year.

Joe

Okay, then we have to find where the break is. The first thing I would check is to see if the APP sensor is working. Determine if the voltage changes based on different pedal positions. If it doesn't, replace the APP. If it does, then we have a break between the pedal and the PCM or the PCM and the throttle position sensor.

Let me know if you have questions.

Joe

When you say throttle assembly, are you referring to the throttle body or the accelerator pedal position sensor in the vehicle above the gas pedal? If I understood correctly, I believe you replaced the throttle body which should have a net throttle position sensor (TPS).

Let me know. We'll figure it out one way or another. LOL

Joe

Hi,

Okay. Then we need to start checking. Here is a list of how the TAC system works. Let me know where you would like to start and I start looking through diagnostic flow charts and send them to you as well.

___________________________________________________

2007 Chevy Truck TrailBlazer 2WD L6-4.2L
Throttle Actuator Control (TAC) System Description
Vehicle Powertrain Management Computers and Control Systems Electronic Throttle Actuator Description and Operation Components Throttle Actuator Control (TAC) System Description
THROTTLE ACTUATOR CONTROL (TAC) SYSTEM DESCRIPTION
Throttle Actuator Control (TAC) System Description

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.

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.

Modes of Operation

Battery Saver Mode

If the powertrain control module (PCM) detects the ignition ON for 10 seconds without the engine running, the PCM will allow the throttle blade to return to the default position. This removes the draw that is present while holding the throttle blade at the calculated idle position.

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.

I have to ask, have you checked for diagnostic trouble codes? I am finding quite a few codes related to the TPS. If you have, let me know what they are.

Let me know.
Joe

What switch? Was it the ignition switch? That is the only one I can think of that can be associated with the one code.

Also, the 1516 is specific to the throttle actuator control system. With this code, there should be information stored in "Freeze Frame" data. If the scanner can read that, check to see what was happening when the code was set.

Now the P1682 is related to either related to a short to ground or an open in the power-train relay, or it is an open or high resistance in the ignition main relay. See pic 1.

Did the replacement of the switch take care of the problem?

Joe

I attached the only pics I have. It is of the power distribution box under the hood, Let me know if it helps.

Joe