Question about 2004 Chevrolet TrailBlazer

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04 trailblazer 6cyl loses power, will restart and idle fine, but will not accelerate . have replaced pcm,throttle position sensor,crank sensor and, cam position sensor.have checked fuel pressure and its fine but now at a loss as to where to look next. vehicle can sit for five minutes and may go for a week before it does it again.

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Lmrobinson....Did you ever figure out what was wrong with your TB? Mine has the exact same issues and we are at a lose! Please, Please help!!!!! you can email me at tarinehimer@yahoo.com if you cant reach me here.

Posted on Aug 24, 2010

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What kind of link is between the gas pedal and engine? Is it a cable or is it electronically connected (like on toyota's?) If it is electronic maybe something is loose or simply doesn't work. If it is a cable then check if throttle plate is opening with cable actuation.

Posted on May 07, 2010

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4 Answers

What does this mean when engine light with down arrow and loses power


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.

Jun 05, 2016 | 2005 GMC Envoy

1 Answer

Check engine light reduce engine power and traction controll off.


It could be the APP sensors or the throttle body throttle position sensors . What DTC'S - diagnostic trouble codes . Need to test the electrical wiring , 5 volt reference voltage. Drive by Wire Function and diagnostics by Wells
REDUCED ENGINE POWER - mass airflow sensor has nothing to do with this problem .
Throttle Actuator Control (TAC)
Reduced Engine Power Mode When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
?€¢
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 motor and the throttle will return to the spring loaded default position.


?€¢
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.




Refer to
?€¢
Powertrain Control Module Description for the 4.8L, 5.3L and 6.0L engine


May 09, 2016 | 2006 Chevrolet Avalanche

2 Answers

Starts and idles, no accelerator response.


Your Denali has Throttle Actuator Control (TAC) System - Electronic throttle control ! Are there any messages on the driver information center ? Reduced engine power ?
Reduced Engine Power Mode When the PCM detects a condition with the TAC system the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
?€¢
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 motor and the throttle will return to the spring loaded default position.


?€¢
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.


You need to have it checked for DTC'S - diagnostic trouble codes , probably a accelerator pedal position (APP) sensor or TPS - throttle position sensor !

Jun 01, 2015 | 2003 GMC Yukon Denali

1 Answer

Loss of power on dash and operates only at idle no matter how far i press on the gas pedal


Throttle Actuator Control (TAC) System Description
You have APP- accelerator pedal position sensors or one of the Throttle position sensors is going bad ! In the (TAC) system ! This is drive by wire or electronic throttle control . If you take it to the dealer or a ASE certified repair shop they can check the DTC'S - diagnostic trouble codes ! This is nothing for a DIYer to mess with ! This system can set 7 different DTC'S

Reduced Engine Power Mode When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
?€¢
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 motor and the throttle will return to the spring loaded default position.

?€¢
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.


Drive by Wire Function and Diagnostics by Wells

May 14, 2015 | 2004 Chevrolet Silverado 2500 Crew Cab

1 Answer

2003 Chevy Trailblazer engine power lose light come on


Hi Steve , your vehicle has electronic throttle control . I don't know if you are aware of this. The gas pedal have position sensors an a wiring connector with 4-6 wires .these wires are connected to the engine computer . an there is a electric motor on the throttle body assembly , the computer opens an closes the throttle . You probably have codes stored in the engine computer .
Reduced Engine Power Mode When the PCM detects a condition with the TAC system the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
?€¢
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 motor and the throttle will return to the spring loaded default position.

?€¢
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.

Drive by Wire Function and diagnostics by Wells

May 04, 2015 | 2003 Chevrolet Chevrolet TrailBlazer

1 Answer

2002 Trailblazer rough idling


First try cleaning the throttle body,make sure you take it off the intake manifold so that the rear side gets cleaned as well. While doing the cleaning, disconnect the battery so that the PCM will reset and relearn to the freshly cleaned throttle body.

Dec 18, 2012 | 2002 Chevrolet TrailBlazer

1 Answer

Have 2006 gmc canyon having trouble with it staying on.3.5 engine starts up,stays on a few seconds then shuts off shows reduced power on panel.won't crank over .have to wait a few minutes then it


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

May 25, 2017 | 2006 GMC Canyon

1 Answer

2005 Mazda 6 4cyl AT Idles high after driving a while.


I would check the pedal position sensor. Do it when it's hot.
Mazda Car 2005-06
  • Accelerator Pedal Position Sensor

    Description & Operation

    A power supply is applied on the Accelerator Pedal Position (APP) Sensor (main) power terminal from the PCM. The ground terminal is grounded with PCM. When the accelerator pedal is moved from the idle position to the fully opened position, the resistance between the accelerator pedal position sensor (main) output terminal and ground terminal will increase according to the depression.
    A power supply is applied on the Accelerator Pedal Position (APP) Sensor (main) power terminal from the PCM. The ground terminal is grounded with PCM. When the accelerator pedal is moved from the idle position to the fully opened position, the resistance between the accelerator pedal position sensor (main) output terminal and ground terminal will increase according to the depression.

Testing

  1. Connect a suitable scan tool to the diagnostic connector. Select APP1 or APP2 percentage.
  2. Turn the ignition switch to the ON position.
  3. Measure the voltage at the PCM terminal and ground with connectors connected:

    APP1-8% load or 0.4 volts with the accelerator pedal releasedAPP1-60% load or 3.0 volts with the accelerator pedal depressedAPP2 -8% load or 0.4 volts with the accelerator pedal releasedAPP2 -60% load or 3.0 volts with the accelerator pedal depressed
  4. If any check above does not meet the specifications, check connectors and wiring between the sensor and PCM. If ok, replace PCM.
  5. If the measured values are outside the standard value range, or if the load % and/or voltage does not change smoothly, replace the sensor.
  1. Connect a suitable scan tool to the diagnostic connector. Select APP1 or APP2 percentage.
  2. Turn the ignition switch to the ON position.
  3. Measure the voltage at the PCM terminal and ground with connectors connected:

    APP1 %-31.0-32.4% with the accelerator pedal releasedAPP1 %-69.8-81.8% with the accelerator pedal depressedAPP2 %-20.2-21.4% with the accelerator pedal releasedAPP2 %-58.8-70.8% with the accelerator pedal depressed
  4. If any check above does not meet the specifications, check connectors and wiring between the sensor and PCM. If ok, replace PCM.
  5. If the measured values are outside the standard value range, or if the load % does not change smoothly, replace the senso

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Jul 23, 2017 | 2005 Mazda 6

1 Answer

Still looking idea on WOT relay. Cuts power to A/C compressor, controlled by PCM


Wide open throttle signal goes to PCM from the TPS, throttle position sensor. mounted on throtle body

eg.
Throttle Position Sensor The throttle position (TP) sensor (Figure 39) is a rotary potentiometer or Hall-effect sensor that provides a signal to the PCM that is linearly proportional to the throttle plate/shaft position. The sensor housing has a three-blade electrical connector that may be gold plated. The gold plating increases corrosion resistance on terminals and increases connector durability. The TP sensor is mounted on the throttle body. As the TP sensor is rotated by the throttle shaft, four operating conditions are determined by the PCM from the TP. Those conditions are closed throttle (includes idle or deceleration), part throttle (includes cruise or moderate acceleration), wide open throttle (includes maximum acceleration or de-choke on crank), and throttle angle rate.

Jul 02, 2009 | Lincoln Town Car Cars & Trucks

2 Answers

Check Engine Light & Dashboard Reads Reduced Engine Power


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....

Jun 20, 2017 | 2007 Chevrolet Uplander

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