GMC Cars & Trucks - Recent Questions, Troubleshooting & Support


Either the teeth are one on key or maybe the tumbler has turned.

GMC Cars &... | Answered 20 hours ago


Have the filter in the transmission checked - they clog and then no fluid can move in the transmission, and the flow of the fluid is what makes gears shift.

GMC Cars &... | Answered 22 hours ago


you eather have a bad fuse or you need a new rear van moter

1999 GMC Safari | Answered Yesterday


Depends on what engine is in the truck. There were several choices. 6 cylinder, small block V8 or big block V8

GMC Cars &... | Answered 2 days ago


I'm pretty sure that there is a video on you tube on how to reset GM speedometers. Give it a shot.

GMC Envoy Cars &... | Answered 3 days ago


Doesn't sound like the all wheel drive is working.

GMC Denali Cars... | Answered on Jan 14, 2019


Are you pressing the lock button to cause this, has your security system or any other electronics systems been serviced or accessed at all in any way start there. Check into the keyless entry and remote system. If gnus helps please click the green button to let me know and have a great day!

2003 GMC Yukon... | Answered on Jan 14, 2019


Sure, you’ll need an aftermarket stereo to take advantage of this. Is it worth that to you? If so it’s only $200 or so for a super nice head unit capable of this ad of today, that includes a back up camera too.

2003 GMC Yukon... | Answered on Jan 14, 2019


WAIT!!!!!! 2 Options- Easy Way or Hard Way, I'll post pitiful the easy way! See pictures below but read the hard way too as it's not nearly as hard as people say, just do your research first but option 2 in the pictures I've attached to this answer is so much easier and just as effective!

1,) If you have broken exhaust manifold bolts(same for headers if you have them) there's no reason to worry about head removal or anything remotely close to TDC. That won't apply to this project. You'll have to remove the front wheels & inner fenders which are plastic. This allows easy access to the exhaust bolts. You must drill them out and I suggest a Ez-Out tool or broken bolt extractor, a left handed drill bit could be helpful too. Either way you go, no need to do all of that extra work for nothing. TDC is relevant when setting a vehicle's timing, yours wouldn't be affected by removing the cylinder heads anyway. Just do it with the motor intact and in the vehicle, see one of the many YouTube videos on this- it's not bad at all! Let me know if I've been helpful by vibking the Green Button and have a great day!

2.) See Attached Pics and then amazon through the link provided to learn more, the customer reviews are particularly helpful!
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2003 GMC Yukon... | Answered on Jan 14, 2019


Your car's fob can't be programmed like that .
Transmitter Programming
Important: Up to 4 transmitters can be programmed. Do not operate or program the transmitters in the vicinity of other vehicles that are in the keyless entry program mode. This prevents the programming of the transmitters to the incorrect vehicle. The order in which the transmitters are programmed is important. The first transmitter programmed will be transmitter #1, and the second transmitter programmed will be transmitter #2. Use care to program the transmitters correctly.
Important: All key fobs must be programmed each time any one fob is programmed. The scan tool must stay connected until all of the transmitters are programmed.
Install a scan tool and navigate to the BCM Module Setup menu.
Select Program Key Fobs.
Follow the scan tool on-screen directions.
When the programming operations have completed, operate the transmitter functions to verify correct system operation.

2004 GMC Canyon | Answered on Jan 13, 2019


The testing procedure is fairly long ,to much to post here . The first test would be to hook up a factory or some other professional type scan tool an check for DTC'S - diagnostic trouble codes .
Auxiliary HVAC Control Module
The auxiliary HVAC control module is a class 2 device that interfaces between the rear seat occupants and the auxiliary HVAC system to maintain auxiliary air temperature and auxiliary air distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all auxiliary HVAC DTCs and settings will be erased from KAM. The auxiliary HVAC control module will perform a recalibration of the electric actuators when commanded with a scan tool or if KAM is lost. This will ensure the actuators are moving with in the calibrated range. During this calibration process the auxiliary blower motor will be disabled for up to 3 minutes.

Do you know what class 2 is ? It is a serial data network for the control modules to talk to each other .

Air Distribution - Auxiliary Control
The auxiliary HVAC system provides ventilation for the rear seat occupants.
The auxiliary mode actuator shares a control circuit with the auxiliary air temperature actuator. The auxiliary mode is controlled by a rotary knob on the auxiliary HVAC control module. If change of position is required for both actuators, then the auxiliary HVAC control module positions the auxiliary air temperature actuator first. All control circuits for the auxiliary actuators are at a low voltage potential until a change of position is required. The module then applies a high voltage potential to the appropriate control circuit, which will rotate the actuator.

Air Speed - Auxiliary
There are two separate controls for the auxiliary HVAC system. There is the front auxiliary blower motor switch and the auxiliary HVAC control module. If the front auxiliary blower motor switch is in any other position than OFF or REAR, then the auxiliary air temperature actuator mimics the set passenger temperature. The auxiliary mode will mimic the primary mode. If the front auxiliary blower motor switch is in the REAR position, then the system will only function with inputs to the auxiliary HVAC control module. If the front auxiliary blower motor switch is in the OFF position, then the auxiliary HVAC control module does not respond to input. The auxiliary HVAC control module can not request A/C operation from the PCM. The rotary blower switch on the auxiliary HVAC control module provides the operator the ability to select several blower speeds. The auxiliary HVAC control module provides a pulse width modulated (PWM) signal to the auxiliary blower motor through the auxiliary blower motor speed control circuit. The auxiliary blower motor changes speed based on the received PWM signal from the auxiliary HVAC control module. Power and ground are provided to the auxiliary blower motor through the battery positive voltage and ground circuits. Power and ground are provided to the auxiliary HVAC control module by the ignition 3 voltage and the ground circuits.

Auxiliary Console Mode Actuator
The auxiliary console mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5 volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the auxiliary HVAC control module grounds one of the control circuits while providing the other with 12 volts. The control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
The auxiliary HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module grounds both control circuits.

Auxiliary Mode Actuator
The auxiliary mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5 volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the auxiliary HVAC control module grounds one of the control circuits while providing the other with 12 volts. The control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
The auxiliary HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module grounds both control circuits.

It's nice to know how thing's work before trying to fix it .

GMC Envoy XL... | Answered on Jan 13, 2019


Could be something as simple as the connection came unplugged. If not, disconnect it at the lug and check it with a test probe to see is there power from the harness to the motor. If no power, check fuses and connection at the sending unit.

2005 GMC Sierra | Answered on Jan 12, 2019

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