2003 Buick Rendezvous CX. Security light on the dash.
I checked all fuses and relays (all are fine). My car wont start. There are times when it will and times when it wont. When I put the key in the ignition, it acts like it will start (the gauges will all come on, you can hear relays working) but no crank over.
Sometimes when I am driving at night (happens during the day too) all lights inside and out will shut down (all while the car is still in motion and running) as if I turned the car off. What can be going on with this?
The problems you are describing could be several different things. They could be related to each other or not. The engine not cranking could be a starter relay problem or the actual starter is going bad. But that would not explain the lights problem you have in your Buick.
These could be related to a wiring problem in the fuse box that has the starter relay and other fuses in it. I would suggest removing a few fuses and relay's from the under hood box and look for corrosion. If water has gotten in there, you would see grime or green stains on the terminals. We have seen this problem several times before.
There could also be a problem with the theft system. If here is the Theft or Security light would either come on the dash or blink. A scan of computer codes would be needed to check for a theft problem.
For the lighting problem you have, this could be a BCM problem, or a faulty ignition switch. That could also explain it if you have a security problem as stated above, or not. An ignition switch is what feeds power to most of the vehicle systems. A problem with this can cause low voltage to the electrical components and make the lights go out like they are.
The ignition switch can also cause all the problems you are having in your Buick. I would have that looked at first. Before taking it to a repair shop, start the truck and then tap on the head of the key and around the ignition with your hand or even a small hammer. Many times that will cause it to act up and you would see the lights flickering on and off. If that happens, have it replaced first, then drive it a while to see if it fixes all the problems you have with starting as well.
Buick Rendezvous Security Light On