GMC Cars & Trucks - Recent Questions, Troubleshooting & Support


Fuel Pump Flow Control Module (LLT)
Mounted under the rear of the vehicle, rear of the fuel tank

GMC Cars &... | Answered 4 hours ago


Eventhough your vehicle is 16 years old, GMC should be informed and may replace the faulty unit if there is a production issue.

GMC Cars &... | Answered Yesterday


You need to identify what each code means and again you could have other codes popping up because a sensor could be depending on another faulty sensor

2009 GMC Acadia | Answered 2 days ago


Can be three things

check fuse

check bulbs

check the brake light switch

GMC Cars &... | Answered 2 days ago


The carbon cannister hoses may be cracked, there might be a rubber fuel line hose leaking too.

2003 GMC Envoy | Answered 3 days ago


your question is realy garbled but I think you are asking about the timing of the cam and the crank sensors usually you have to have them both replaced at same time which means you can see the NO1 position on the cam and the position of the crank and thats with the cover off but I found out from another friend that if you go onto YouTube and request How To set timing on the Cam shaft and Crank shaft sensors you will get a video. MAKE SURE YOU SPELL IT ALL RIGHT OTHERWISE YOU WILL NOT FIND IT. Sorry about the Caps but wanted your attention use my spelling. Good Luck

1997 GMC Sierra | Answered on Nov 14, 2019


Backup Lamps
The backup lamp request signal is sent from the PCM to the BCM on the GMLAN serial data system. This signal is based on the park neutral position (PNP) switch signal. The BCM supplies voltage to the backup relay and to the automatic day/night mirror when the vehicle is in reverse. The backup relay supplies a voltage on the backup lamp supply voltage circuit to the backup lamps and trailer backup circuit.

Maybe the back up lamps relay is stuck closed sending battery voltage to the lights all the time . The factory repair manual said this back up lamp relay is in the under hood fuse / relay box. It also states the relay is a PCB - printed circuit board relay , soldered directly on the circuit board inside the fuse / relay center .

GMC Cars &... | Answered on Nov 12, 2019


Door Lock System Components
The power door lock system consists of the following components:
• Driver door module (DDM)
• Passenger door module (PDM)
• Door lock relay--Located in the instrument panel (I/P) fuse block and controls the locking of the rear doors.
• Door unlock relay--Located in the I/P fuse block and controls the unlocking of the rear doors
• Body control module (BCM)
• IP BEC
• Reversible door lock actuators in each door

Driver and Passenger Lock System Operation
The front power door lock switches are integral components of the driver door module (DDM) and passenger door module (PDM). The switches are two-position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitor these inputs and send a LAN message indicating a change in the switch position. Modules, that activate the power door lock motors, receive the LAN message and activate the motor in the appropriate direction to lock or unlock the vehicle doors. The body control module (BCM) upon receipt of a lock or unlock signal will control the rear door lock or unlock relays and also send a LAN message to the DDM and PDM to perform the commanded function.
The modules that activate the power door lock motors are:
• DDM (driver door lock actuator)
• PDM (passenger front door lock actuator)
• BCM (both rear door lock actuators)
The DDM and PDM are directly connected to the respective door lock actuator through the door lock motor lock and unlock circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other, causing the doors to lock or unlock.
The rear passenger doors are controlled by the BCM through the rear door lock/unlock relay which is incorporated onto the printed circuit board in the LH BEC. The BCM controls the unlock relay by providing ground to energize the coil and controls the lock relay by providing battery voltage to energize the relay coil. This energizes the relay and allows voltage to be applied to either the door lock motor lock or unlock circuits. Since the other side of the door lock actuator is connected to the normally closed contacts of the opposing relay to ground, the doors lock or unlock.

GMC Acadia Cars... | Answered on Nov 10, 2019


Any codes? Fuel filter, air filter, tune-up, fuel injectors.

GMC Cars &... | Answered on Nov 10, 2019


Start by checking for a bad switch at the lights and the doors. This will take a little work to get to the switch. I've seen a bad door switch keep the light on.

2007 GMC Envoy | Answered on Nov 09, 2019


They wouldnt have a common fuse, so I'd look for a bad ground. Search online for a wiring diagram that shows ground locations.

GMC Cars &... | Answered on Nov 09, 2019

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