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Posted on Jul 15, 2017
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2003 Yukon Denali XLT lights flicker, rpm goes up and down when on park or stopped or driving and slow speeds. Sometimes it turns off. I thought it might be bad spark plugs or cables so I changed them and still the same problem. The battery is only about a year old. We tried Fuel injection fluid a few of them actually and not much changed. When stopped and stepping on the break it reves up and down like it wants to jump.

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Jeff Armer

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  • GMC Master 15,575 Answers
  • Posted on Jul 19, 2017
Jeff Armer
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Joined: Nov 22, 2012
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Your vehicle has electronic throttle control . Position sensor's in the gas pedal an the throttle body , inputs to the Throttle Actuator Control Module
The TAC module is the control center for the throttle actuator control system. The TAC system is self-diagnosing and provides diagnostic information to the PCM through a dedicated serial data line. The TAC achieves throttle positioning by providing a pulse width modulated voltage to the TAC as directed by the PCM.

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 components include the following:
• The accelerator pedal position (APP) sensors
• The throttle body assembly
• The throttle actuator control module
• The powertrain control module (PCM)
Accelerator Pedal Position (APP) Sensor
The accelerator pedal assembly contains 2 individual APP sensors within the assembly. The accelerator pedal position (APP) sensors 1 and 2 potentiometer type sensors each with 3 circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
The APP sensors are used to determine the pedal angle. The control module provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module with signal voltage proportional to pedal movement. APP sensor 1 signal voltage is low at the rest position and increases as the accelerator pedal is applied. APP sensor 2 signal voltage is high at the rest position and decreases as the accelerator is applied.
Throttle Body Assembly
The throttle body assembly consists of the throttle body, the throttle position (TP) sensors, and the throttle actuator motor. The throttle body functions similar to a similar to a conventional throttle body with the following exceptions:
• An electric motor opens and closes the throttle valve.
• The throttle blade is spring loaded in both directions and the default position is slightly open.
• There are 2 individual TP sensors within the throttle body assembly.
The TP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
The TP sensors are used to determine the throttle plate angle. The control module provides each TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensors then provide the control module with signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens.

Flickering light's could be caused by a bad diode in the alternator . Fluctuating idle could be caused same alternator problem or dirty throttle plate.
Throttle Body Cleaning To Restore Idle Quality

5 Related Answers

Anonymous

  • 1 Answer
  • Posted on Jul 24, 2008

SOURCE: climate control 04 yukon denali

I would try resetting both sides. i.e., Set both sides to hot, then back down to cool. Also check your fuse. I am not sure, but would think, you have a fuse for all these different items. It is time consumming, but look through and find your blown fuse. Hope it helps.

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Marvin

  • 85242 Answers
  • Posted on Dec 17, 2008

SOURCE: 2003 yukon xl 5.3l flexfuel all plugs lean on passenger side

P0131 - Heated Oxygen Sensor (HO2S) Circuit Low Voltage

P1133 - Heated Oxygen Sensor (HO2S) Insufficient Switching Bank 1 Sensor 1


Bank 1 Sensor 1
P0300 - Engine Misfire Detected

I would check for vacuum leaks, maybe intake or brake booster

Anonymous

  • 36 Answers
  • Posted on Aug 14, 2009

SOURCE: 02 yukon denali security light stays on will not

Several GM products, including the Chevrolet Impala and Malibu, the Oldsmobile Alero, the Pontiac Grand Prix, and Saturn Ion, have issues with the Security light coming on. This is many times an indication of a failing Body Control Module (BCM). Initially, the Security light will come on then go off, progressing to a constant on light, before the car will refuse to start. Other symptoms may include erratic action of electronics, a clicking sound coming from the glove box, and the air conditioning failing to blow cold air. I recommend a shop that specializes in the electronic systems of vehicles to diagnosis and make the necessary repairs. They should keep the car until they replicate the symptoms described. A new BCM from GM should cost about $230; plan on another $200 for them to diagnose the problem, replace the unit, and program the new unit. The dealers quote between $700 and $1,100 for the same repair. My experience and the experiences I have read on the internet, indicate the new BCM should last only about a year.

Anonymous

  • 7353 Answers
  • Posted on Oct 30, 2009

SOURCE: 2006 Yukon Denali, oil pressure gauge malfunction

Most likely the oil pressure sensor is bad. Its located in the very rear of engine on top of bell housing area.

john h

  • 29494 Answers
  • Posted on Nov 26, 2009

SOURCE: gmc yukon has the abs & parking brake light

you have to fix the problem with ur brakes- first check the wiring ,connectors and connection clips to the abs sensors and modulator if looks ok than have truck scanned some auto stores such as auto zone / advanced auto do it for free the code will give u a start point towards fixing ur problem--visual inspection of brakes doesnt always show problem

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Related Questions:

0helpful
1answer

Working on a 2003 Yukon Denali kl,was running great, stopped to check mail and now it will not move fwd or reverse, can shift through gears but truck will not move, any help is greatly appreciated

Do you have a check engine light
4L60E check fuses before working on your chevy transmission
https://www.youtube.com/watch?v=pbaj0dOG2vg

GMC Yukon Denali: he cant shift into park..shifter
https://www.justanswer.com/gm/3z762-gmc-yukon-denali-can-t-shift-park-shifter.html

I put my truck into drive or reverse n it will not move at all what is causeing this to happen
https://www.cargurus.com/Cars/Discussion-t14601_ds575443

Shift but won't go into gear just revs
https://www.transmissionrepaircostguide.com/topic/shift-but-wont-go-into-gear-just-revs/

I have had vehicles where the speed sensor, MAF, MAP and throttle body did not let them shift as they should but the vehicle did shift. I have put several links above. Just to make sure if you have check engine light find out the code. Make sure you check transmission fluid with engine on and in park, emergency brake on at normal operating temperature. ( May sound bad but I have had to tell people above 30 about this and they said it was the first they heard of it). I will say the thing which stands out to me is check shifter cable. Check fuses. I did see a link which suggested brakes locked up but I assume the truck is not even trying to move.

GMC Yukon (2003 - 2004) - fuse box diagram
https://www.autogenius.info/gmc-yukon-2003-2004-fuse-box-diagram/


0helpful
1answer

Traction active, service ride control, service stability, sometimes brake light on dash comes on with or without abs light. also noticed drop in power (max speed 10mph) also noticed air bag lights in...

not that this is going to really help your overall problem but I can tell you that smelling antifreeze in the cabin and if the foormats are wet in the front then it is probably your heater core that has sprung a leak. Think of your heater core as a mini radiator but inside the vehicle and they are usually tucked up inside the dash somewhere and is usually quite expensive to have repaired because of all the labor involved. I just replaced mine in my 2001 Mercury Grand Marquis and it took me about 10 hours to change out. And i am a mechanic.As for your electrical problems I would personally contact the dealership and as them about recalls or technical bulletins concerning your 2003 GMC Yukon xl denali. Good Luck.
0helpful
2answers

The speedometer gauge and RPM gauge is not working. The speedometer gauge goes to the max while I am driving. The car itself seems to be running ok. Help! It is a Yukon Denali 2005.

I suspect that your sender is malfunctioning. Todays speedometers and RPM is sent from a sensor/sender near the drive shaft. A magnet on the drive shaft is sensed and the revolutions are converted to RPM and speed.

For information see:

http://wiki.answers.com/Q/Speedometer_on_2003_Yukon_XL_doesn%27t_work_most_of_the_time_is_this_a_common_problem_how_much_to_fix_it
0helpful
1answer

Oil light flickering on when @ a stop light

sounds like idle speed is to low,need to have rpm checked against manuf.suggested rpm
15helpful
4answers

Speedometer not working properly

There was not a recall, but there was a class action settlement where GM agreed to extend the warranty on certain vehicles for this problem. Check www.gmspeedometerrecall.com to see if you qualify.
1helpful
1answer

03 Yukon denali park brake warning wont turn off

hi for info the brakes warning light on dash is also an indication that brake fluid level is low? or there may be a leak resulting in fluid level drop ? also considering age of car you may need to inspect brake pads wear ? if your car has low brake pads wear indicators attached to pads ? or the hand brake switch req's checking to ensure it is being pushed to off position when h/brak is down ? so fluid level low is the obviouse 1st check as fluid will displace from reservoir as pads wear low hence the level indicator on fill cap trips on may i suggest if it is low level b4 you top up? check your b/pads if you have not done so recently? or replaced since new ? hope this helps you locate problem best wishes from the uk
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