2000 chevy impala 3.4L. Check engine light and air bag light comes on then the battery light and brake light comes on then all of them go off. I had a dead battery that got replaced that's all. Question = my car in the morning when I put the key in the ignition and turn it to start all I hear is a humming noise from the back of the car which lets me know the fuel pump is working, well it should its been replaced, all of the lights come on air works headlights work but the dash lights go off when I try to start it and it will not start. I have to try to start it several times before it will finally start. Then while driving the air bag light comes on then a few minuets later the battery light and brake light come on flash then all 3 lights go off. The check engine light is still on. The weird thing is it only does this in the morning. Once it is started it starts the rest of the day. What could be the problem?
Answer: With all of these lights on, there will be trouble codes stored in one or more of the computers. The first step is to have the computer scanned for codes. That will usually give an indication as to what system might be causing all of these problems. Several of the computers may have codes that are the same or at least related to one common problem.
Start with the basics first. Check for loose or corroded battery cables, loose starter wires or engine harness ground wires, etc.
With that said, the warning lights and problems you describe really sounds like your Impala has a bad ignition switch. The ignition switch is what powers up most of the vehicles systems. When turning the key and the engine will not crank over- but all of the lights work, that says there is either no power getting to the starter or there is a theft / security problem. Since you did not mention a theft or security light, I will assume that is not the problem.
The dash lights going out while trying to crank is also a sign of a bad ignition switch. When these switches go bad, it is not sending the proper amount of voltage to power up the circuits, so the dash lights go out. Also, when driving and the battery, brake and airbag lights come on- this could also be a sign of a low voltage problem. If the respective computers are not getting or seeing the proper voltage, they will turn on their warning lights.
Try tapping on the head of the key with a small hammer while the car is running normally. If this causes lights to flicker or any other electrical problems, then the ignition switch is faulty and needs to be replaced. After replacement, a theft system relearn will need to be done.
Another possibility is a bad Body Control Module (BCM). This computer controls all of the warning lights you are having issues with and the theft / security system for engine cranking. This would be more difficult to diagnose. A scan tool that reads live module data would be needed. Again, a scan of the computer codes may show a problem related to the BCM in all the other modules.