Question about 2004 GMC Sierra 2500

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Display on dash reads '' reduced engine power '' . will start & run but have no throttle control, engine idles more rpm than normal, left headlight is dim, turn key off then have to turn back on for engine to die. 2003 gmc 2500 sierra.

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  • locksmith33 May 11, 2010

    check your throttle position sensor located on youre throttle body. and is it when you towing?

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Is this a gas or diesel? Usually this is to protect an engine if there is a fault found by the truck's computer. It can be related to oil level, temp, or pressure. Could be related to the antifreeze. Check the levels. Also you said something about a headlight being dim. So You will need to check that Curcuit out as well. Could be related but a scan-tool would be needed to look a parameters.

Posted on Nov 19, 2009

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Throdlebody and gas peddle out of sink won,t go faster than 30


If you would like help we would need the DTC - diagnostic trouble code .Is their a Reduced Engine Power Mode message showing on the instrument cluster ?
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.
IF you do not know this your best bet would be to take to a qualified repair shop .
DTC P0506
DTC P0507
The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

Jan 05, 2017 | Cars & Trucks

1 Answer

Pontiac grand prix 2007 car shutting off, with Start disabled throttle control module.


It doesn't say module , Starting Disabled Due To Electronic Throttle Control !
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 (APP) 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 APP sensors
• The throttle body assembly
• The powertrain control module (PCM)
Normal Mode
During the operation of the throttle actuator control (TAC) system, several modes or functions are considered normal. The following modes may be entered during normal operation:
• Minimum pedal value--At key-up, the powertrain control module (PCM) updates the learned minimum pedal value.
• Minimum throttle position (TP) values--At key-up, the PCM updates the learned minimum throttle position value. In order to learn the minimum throttle position value, the throttle blade is moved to the closed position.
• Ice break mode--If the throttle is not able to reach a predetermined minimum throttle position, the ice break mode is entered. During the ice break mode, the PCM commands the maximum pulse width several times to the throttle actuator motor in the closing direction.
• Battery saver mode--After a predetermined time without engine RPM, the PCM commands the battery saver mode. During the battery saver mode, the TAC module removes the voltage from the motor control circuits, which removes the current draw used to maintain the idle position and allows the throttle to return to the spring loaded default position.
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 PCM will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
• Limited throttle mode--The PCM will continue to use the accelerator pedal for throttle control however the maximum throttle opening is limited.
• Throttle default mode--The PCM will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
• Forced idle mode--The PCM will perform the following actions:
- Limit engine speed to idle by positioning the throttle, or by controlling the fuel and spark if the throttle is turned off.
- Ignore the accelerator pedal input.
• Engine shutdown mode--The PCM will disable fuel and de-energize the throttle actuator.

DTC P2101
DTC P2107
DTC P2108
DTC P2119
DTC P2120
DTC P2125
DTC P2135
DTC P2138 You need to see which of these codes

Nov 16, 2016 | 2007 Pontiac Grand Prix

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

1 Answer

Reduce power light on has no throttle and keeps giving throttle accuator cdes


2003 Silverado 2500HD REDUCED ENGINE POWER - Discussion on Topix

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Oct 28, 2015 | Cars & Trucks

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

Correct code P0504?


What Colorado do you have ? 2 wheel or 4 wheel drive ? Sport ,sport LS 3.5L , Z71, Z71 LS. etc. what size engine ? an does it have electronic throttle control ? I have factory service info an it is not showing that code .
DTC P0506

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0506 Idle Speed Low
DTC P0507

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0507 Idle Speed High
Cleaning the throttle body mite take care of it !
Cleaning Cleaning An Electronic Throttle Body Safely

Jan 31, 2015 | 2005 Chevrolet Colorado

2 Answers

Why does ford focus 2000 rev high and return to normal when I start the car?


Not to sure myself but if you go on to the following there are some great users on there that are willing to help anybody with there problems , 9 out of 10 problems with any make of car etc are answered for you. https://www.facebook.com/groups/199673323387831/

Jun 14, 2014 | 2000 Ford Focus

1 Answer

Truck dies when idling


HI
first I would like to tell you, do this procedure only if the 5th digit of your VIN is C or K.

Description

The engine control module (ECM) learns the idle position of the throttle plate to ensure the correct idle. Anytime the throttle body is cleaned or replaced, the ECM must learn the new throttle position. The idle may be unstable or a DTC may set if the throttle position is not learned.

Conditions for Running the Throttle Learn Procedure

• DTCs P0101, P0102, P0103, P0107, P0108, P0111, P0112, P0113, P0506, and P0507 are not set.

• The engine speed is between 450-4,000 RPM.

• The manifold absolute pressure (MAP) is greater than 5 kPa.

• The mass air flow (MAF) is greater than 2 g/s.

• The ignition 1 voltage is greater than 10 volts.

Throttle Learn

Important: Do NOT perform this procedure if DTCs are set. Refer to Diagnostic Trouble Code

(DTC) List - Vehicle.

1. Start and idle the engine in PARK for 3 minutes.

2. With a scan tool, monitor desired and actual RPM.

3. The ECM will start to learn the new idle cells and Desired RPM should start to decrease.

4. Ignition OFF for 60 seconds.

5. Start and idle the engine in PARK for 3 minutes.

6. After the 3 minute run time the engine should be idling normal.

Important: During the drive cycle the check engine light may come on with idle speed DTCs. If idle speed codes are set, clear codes so the ECM can continue to learn.

* If the engine idle speed has not been learned the vehicle will need to be driven at

speeds above 70 km/h (44 mph) with several decelerations and extended idles.

7. After the drive cycle, the engine should be idling normally.

* If the engine idle speed has not been learned, turn OFF the ignition for 60 seconds

and repeat step 6.
8. Once the engine speed has returned to normal, clear DTCs.
Good Luck

Mar 04, 2014 | 1995 GMC Sierra

1 Answer

Car accelerates when air conditioning is on


100% normal
most cars raise idle RPM by 200 RPM
100% normal if it was 200.
only at idle. not moving ,ever.

my guess the accelerates means moving. some will use that word for RPM only.
why would any car do that.
answers:
1: ECU?PCM thinks the car is idling
bad TPS sensor or not calibrated.

2: on fly by wire (throttle by wire) the CEL Glows, running, is it> and if yes, why on scan the errors
TBW , has lots of issues, did you read all TSBs on the car, most cars
TBW cars, the TSBs bleed red with issues.
TBW means Throttle by Wire, TSB are trouble bulletins.

when a TBW car has problems, it can go to limphome.
limphome causes out of control idle. and lost engine power
many cars , kill the A.C in limphome. so as not to overheat the engine
or give you more power ,now that 1/2 was lost in limphome.
(passing safety is an issue here)\

so back up

does car dash CEL lamp glow , running engine.and for sure driving
if yes, do not drive car, scan the PCM and find what is wrong.
all cars, 1988 to now. (USA cars have OBD tech)



Aug 30, 2013 | 2007 Honda CR-V

1 Answer

Sitting in car in parking lot with engine running - it dies, won't turn over... I get a jump start No changes in termperature gages at all Idles rough, check engine light on, reduced engine power reading -...


Hi and welcome to FixYa!
It is safe to drive and I assume that you are on limp mode. This is to restrict the speed to avoid further damage to the engine. You can be facing some sensor issues like the MAF (mass air flow) sensor or TPS (throttle position sensor). If one of these sensor is faulty the car tends to run sluggish, run rough or may even result to stalling.

Have the sensors replaced and observe how it goes. This can fix the issue.

Hope this helps and thank you for using FixYa! Have a good one!

Feb 17, 2011 | 2003 GMC Yukon XL

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