Liftgate opens when doors are opened
November 30th, 2015, 10:36 PM
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Liftgate opens when doors are opened
I have an 07 Suburban LTZ and all of a sudden the liftgate has a mind of its own. It will automatically open when you shut the ignition off and open a door. (it does this most of the time now, not every time.) The close switch on the bottom of the liftgate stops working once this occurs. (if I pull the battery for a bit everything goes back to working, until it opens on its own again.) This just started happening less than a week ago.
sidenote: the glass release switch was broken when I bought the truck so I replaced it and it worked for a few months and hasn't worked since. not sure if this might be related.....
sidenote: the glass release switch was broken when I bought the truck so I replaced it and it worked for a few months and hasn't worked since. not sure if this might be related.....
December 2nd, 2015, 9:01 AM
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Welcome to the forum...
I suspect that you are getting a stray signal to the open command for the hatch... if you replaced a switch, you might want to revisit that connection as there may be signal leakage that is feeding back through the system and the hatch thinks it being told to open...
Remember your electrical system is not just a dumb 12v open closed circuit anymore it's and computer network and many of the functions are controlled by signals from/to the the BCM or body control module... if the BCM sees what it thinks is a open signal from the hatch it will open, and a poor connection from another switch in the area can mimic that hatch signal...
Revisit your repair and the harness, also consider removing and reseating the drivers door switch connections as a back up.
I suspect that you are getting a stray signal to the open command for the hatch... if you replaced a switch, you might want to revisit that connection as there may be signal leakage that is feeding back through the system and the hatch thinks it being told to open...
Remember your electrical system is not just a dumb 12v open closed circuit anymore it's and computer network and many of the functions are controlled by signals from/to the the BCM or body control module... if the BCM sees what it thinks is a open signal from the hatch it will open, and a poor connection from another switch in the area can mimic that hatch signal...
Revisit your repair and the harness, also consider removing and reseating the drivers door switch connections as a back up.
December 3rd, 2015, 7:38 PM
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Thank you for your reply! I am currently out of town for work so I will address that connection when I return home. However in the meantime my wife informed me that the nav screen was black but the radio was still playing. The controls on the wheel could change stations and volume however the mute button was inop. She tried restarting the truck 2 times to see if it would correct itself but it didnt. about 15 minutes later, while driving, the screen came back on and the mute button started working. Im wondering if there is not an issue with the BCM??? I should also add that the window switches on the rear doors randomly dont work, but the drivers door could still control them. All of these items have some link to the bcm which is why im considering this as an option.....
Last edited by aborgardt; December 3rd, 2015 at 7:40 PM.
December 4th, 2015, 8:11 AM
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It might be worth reseating all of the connections that go to the BCM before shotgun replacing it.
Be sure to disconnect the battery prior to removing the connections to the BCM, if you do end up replacing the BCM it will likely require programming by a dealership to enable all of the options...
A brief descrip of the functions of the BCM for the 07 and its location under the dash...
2007 Chevrolet Tahoe - 2WD | Avalanche, Escalade, Suburban, Tahoe, Yukon (VIN C/K) Service Manual | Document ID: 1740403
--------------------------------------------------------------------------------
Body Control System Description and Operation
The body control system consists of the body control module (BCM), communications, and various input and outputs. Some inputs, outputs and messages require other modules to interact with the BCM. The BCM also has discrete input and output terminals to control the vehicle's body functions. The BCM is wired to the GMLAN high speed serial data buss and the GMLAN low speed serial data buss and acts as a gateway between them. If the BCM does not communicate the vehicle will not start due to the inability of the engine control module (ECM)/powertrain control module (PCM) and theft deterrent module (TDM) to communicate without the BCM providing the gateway function.
Power Mode Master
This vehicles body control module (BCM) functions as the power mode master (PMM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determination the power mode that will be sent over the serial data circuits to the other modules that need this information, and so the PMM will activate relays and other direct outputs of the PMM as needed. Refer to Power Mode Description and Operation for a complete description of power mode functions.
Serial Data Gateway
The body control module (BCM) in this vehicle functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the GMLAN high speed buss and the GMLAN low speed buss for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.
One example of this necessary communication is the communication between the engine control module (ECM)/powertrain control module (PCM) which is high speed serial data and Theft Deterrent Module which is low speed serial data. If these modules can not exchange information, the vehicle will not start.
Communication between the BCM and a scan tool can be on the high speed GMLAN network or low speed GMLAN network. If one network is lost, the BCM can still communicate with the scan tool. A lost communication DTC typically is set in modules other than the module with a communication failure.
Body Control Module
The various body control module (BCM) input and output circuits are described in the corresponding functional areas indicated on the BCM electrical schematics. Some BCM functions with the subsystems may be as a gateway only or as an enable for the system. The BCM related systems/subsystems include, but are not limited to the following:
• Antilock Brake System (ABS)--Refer to ABS Description and Operation .
• Automatic Day-Night Mirror--Refer to Automatic Day-Night Mirror Description and Operation .
• Cruise Control System--Refer to Cruise Control Description and Operation .
• Electrical Power Management (EPM)--Refer to Electrical Power Management Description and Operation .
• Exterior Lighting--Refer to Exterior Lighting Systems Description and Operation .
• Horn System--Refer to Horns System Description and Operation .
• HVAC--Refer to Air Delivery Description and Operation and Air Temperature Description and Operation .
• Instrument Cluster Indicator Control--Refer to Instrument Cluster Description and Operation .
• Interior Lighting--Refer to Interior Lighting Systems Description and Operation .
• Power Door Lock System--Refer to Power Door Locks Description and Operation .
• Rear Window Defogger System--Refer to Rear Window Defogger Description and Operation .
• Redundant Steering Wheel Controls--Refer to Steering Wheel Controls Description and Operation .
• Remote Function Actuation (RFA) Control--Refer to Keyless Entry System Description and Operation .
• Retained Accessory Power (RAP)--Refer to Retained Accessory Power (RAP) Description and Operation .
• Shift Lock Control System--Refer to Automatic Transmission Shift Lock Control Description and Operation .
• Starting System--Refer to Starting System Description and Operation .
• Supplemental Inflatable Restraint (SIR) System--Refer to SIR System Description and Operation .
• Suspension System--Refer to Electronic Suspension Control Description and Operation .
• Theft Deterrent--Refer to Content Theft Deterrent (CTD) Description and Operation .
• Tire Pressure Monitor (TPM) System--Refer to Tire Pressure Monitor Description and Operation .
• Wiper/Washer System Functions--Refer to Wiper/Washer System Description and Operation .
Export Body Control Module
The export body control system has an additional body control module located in the rear of the vehicle. This additional body control module is referred to as the XBCM. The XBCM has discrete input and output terminals to control additional vehicle body functions not supported by the primary body control module (BCM). The XBCM is wired to the GMLAN low speed serial data buss and the BCM and acts as a gateway between them. If the XBCM does not communicate, various rear end lighting such as rear fog lamps and trailer lighting will be impaired.
The various input and output circuits are described in the corresponding functional areas indicated on the XBCM electrical schematics. Some XBCM functions with the subsystems may be as a gateway only or as an enable for the system. The XBCM related systems/subsystems include, but are not limited to the following:
• Exterior lighting--Refer to Exterior Lighting Systems Description and Operation .
• Instrument cluster indicator control--Refer to Instrument Cluster Description and Operation .
• Theft deterrent--Refer to Content Theft Deterrent (CTD) Description and Operation .
Be sure to disconnect the battery prior to removing the connections to the BCM, if you do end up replacing the BCM it will likely require programming by a dealership to enable all of the options...
A brief descrip of the functions of the BCM for the 07 and its location under the dash...
2007 Chevrolet Tahoe - 2WD | Avalanche, Escalade, Suburban, Tahoe, Yukon (VIN C/K) Service Manual | Document ID: 1740403
--------------------------------------------------------------------------------
Body Control System Description and Operation
The body control system consists of the body control module (BCM), communications, and various input and outputs. Some inputs, outputs and messages require other modules to interact with the BCM. The BCM also has discrete input and output terminals to control the vehicle's body functions. The BCM is wired to the GMLAN high speed serial data buss and the GMLAN low speed serial data buss and acts as a gateway between them. If the BCM does not communicate the vehicle will not start due to the inability of the engine control module (ECM)/powertrain control module (PCM) and theft deterrent module (TDM) to communicate without the BCM providing the gateway function.
Power Mode Master
This vehicles body control module (BCM) functions as the power mode master (PMM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determination the power mode that will be sent over the serial data circuits to the other modules that need this information, and so the PMM will activate relays and other direct outputs of the PMM as needed. Refer to Power Mode Description and Operation for a complete description of power mode functions.
Serial Data Gateway
The body control module (BCM) in this vehicle functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the GMLAN high speed buss and the GMLAN low speed buss for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.
One example of this necessary communication is the communication between the engine control module (ECM)/powertrain control module (PCM) which is high speed serial data and Theft Deterrent Module which is low speed serial data. If these modules can not exchange information, the vehicle will not start.
Communication between the BCM and a scan tool can be on the high speed GMLAN network or low speed GMLAN network. If one network is lost, the BCM can still communicate with the scan tool. A lost communication DTC typically is set in modules other than the module with a communication failure.
Body Control Module
The various body control module (BCM) input and output circuits are described in the corresponding functional areas indicated on the BCM electrical schematics. Some BCM functions with the subsystems may be as a gateway only or as an enable for the system. The BCM related systems/subsystems include, but are not limited to the following:
• Antilock Brake System (ABS)--Refer to ABS Description and Operation .
• Automatic Day-Night Mirror--Refer to Automatic Day-Night Mirror Description and Operation .
• Cruise Control System--Refer to Cruise Control Description and Operation .
• Electrical Power Management (EPM)--Refer to Electrical Power Management Description and Operation .
• Exterior Lighting--Refer to Exterior Lighting Systems Description and Operation .
• Horn System--Refer to Horns System Description and Operation .
• HVAC--Refer to Air Delivery Description and Operation and Air Temperature Description and Operation .
• Instrument Cluster Indicator Control--Refer to Instrument Cluster Description and Operation .
• Interior Lighting--Refer to Interior Lighting Systems Description and Operation .
• Power Door Lock System--Refer to Power Door Locks Description and Operation .
• Rear Window Defogger System--Refer to Rear Window Defogger Description and Operation .
• Redundant Steering Wheel Controls--Refer to Steering Wheel Controls Description and Operation .
• Remote Function Actuation (RFA) Control--Refer to Keyless Entry System Description and Operation .
• Retained Accessory Power (RAP)--Refer to Retained Accessory Power (RAP) Description and Operation .
• Shift Lock Control System--Refer to Automatic Transmission Shift Lock Control Description and Operation .
• Starting System--Refer to Starting System Description and Operation .
• Supplemental Inflatable Restraint (SIR) System--Refer to SIR System Description and Operation .
• Suspension System--Refer to Electronic Suspension Control Description and Operation .
• Theft Deterrent--Refer to Content Theft Deterrent (CTD) Description and Operation .
• Tire Pressure Monitor (TPM) System--Refer to Tire Pressure Monitor Description and Operation .
• Wiper/Washer System Functions--Refer to Wiper/Washer System Description and Operation .
Export Body Control Module
The export body control system has an additional body control module located in the rear of the vehicle. This additional body control module is referred to as the XBCM. The XBCM has discrete input and output terminals to control additional vehicle body functions not supported by the primary body control module (BCM). The XBCM is wired to the GMLAN low speed serial data buss and the BCM and acts as a gateway between them. If the XBCM does not communicate, various rear end lighting such as rear fog lamps and trailer lighting will be impaired.
The various input and output circuits are described in the corresponding functional areas indicated on the XBCM electrical schematics. Some XBCM functions with the subsystems may be as a gateway only or as an enable for the system. The XBCM related systems/subsystems include, but are not limited to the following:
• Exterior lighting--Refer to Exterior Lighting Systems Description and Operation .
• Instrument cluster indicator control--Refer to Instrument Cluster Description and Operation .
• Theft deterrent--Refer to Content Theft Deterrent (CTD) Description and Operation .