Vehicle stays on after key removal also intermittent no start issue?

2004 GMC ENVOY
125,000 MILES • 4.2L • V8 • 4WD • AUTOMATIC
Avatar
JAKE TYRANUS
  • MEMBER
  • 4 POSTS
Greetings esteemed automotive experts,

I write to you in hopes of acquiring professional insights into an ongoing issue with my vehicle listed above, a vehicle which has provided dependable service over the years. I have always ensured diligent maintenance; however, recent malfunctions have presented challenges that elude resolution.

Approximately one year ago, my car began exhibiting signs of battery drain. It required frequent jump-starts, prompting me to replace the battery. Upon further drain incidents, I returned to the battery retailer for inspection. No defects were found in the new battery; rather, the car radio was identified as the source of the power draw. The radio was consequently disconnected, and the battery drain ceased.

Fast-forward a year, with the radio still disconnected, my car now presents a starting issue. After being parked for two to three hours, the car struggles to start. The engine appears to labor, attempting to turn over but without initial success. The interior and exterior lights, however, remain constant and do not dim during this process. The car usually starts on the second or third attempt, and, in rare cases, a fourth attempt is needed.

Simultaneously, my car occasionally continues to run after being switched off—one out of approximately ten instances. The engine remains functional, even allowing for revving. However, upon pressing the brake pedal, the engine shuts off abruptly and the vehicle shakes considerably. Notably, these violent shakes also occur when the car successfully starts on the second attempt but are absent on third or fourth attempts.

Another potentially related observation is a clicking or clinking noise originating from the gear shift area, primarily while braking. It's unclear whether this is connected to the other issues, but it seems significant enough to mention.

Lastly, despite recent brake disk replacements, I've noticed that the car sometimes exhibits prolonged stopping times. Following a stop, the car will idle for about a minute before the engine begins to shake, as if under some form of strain or distress.

I am eagerly seeking your wisdom and guidance to diagnose these issues. Any suggestions on potential causes, possible fixes, and preventive measures would be greatly appreciated.

Thank you in advance for your time and expertise.
Jul 7, 2023 at 6:39 AM
Advertisement
Avatar
STRAILER
  • Experienced Mechanic
  • 55,249 POSTS
It sounds like you could have a couple different problems, but we should start by doing a CAN scan because it sounds like the BCM is going out. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Here is how to change the BCM out in case a code comes up for it. You can get a preprogrammed unit by searching Google or Ebay. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.
Jul 8, 2023 at 4:59 AM
Avatar
JAKE TYRANUS
  • MEMBER
  • 4 POSTS
Hey! Thank you very much. As i went, to attempt to turn on the car. Now it does not even turn on. The battery was drained. But nothing at all was left on in the car. I jump started it and went to the mechanic, who then did a few tests and showed me the spark plugs and how they needed changing. So, i changed the spark plugs and the car turned on like normal. Due to battery being drained all the errors were gone when he wanted to scan it. He did a test on the battery and told me it has nothing to do with the battery. I went home. Next day the battery drained again.
Jul 14, 2023 at 9:28 AM
Avatar
JAKE TYRANUS
  • MEMBER
  • 4 POSTS
Oh, and he manually checked the motherboard for anything obvious, and nothing was physically obvious. Now with no errors, and nothing on in the car at all. I do not know what it is even possible to do now.
Jul 14, 2023 at 9:30 AM
Avatar
STRAILER
  • Experienced Mechanic
  • 55,249 POSTS
I have seen the BCM problem be intermittent so I would drive the car to see what happens, maybe it was a bad connection at the BCM and now it is fixed by taking the electrical connectors off and on. Let me know what happens.
Jul 15, 2023 at 3:22 AM
Avatar
JAKE TYRANUS
  • MEMBER
  • 4 POSTS
Well, i still need to see why the battery is being drained before that because every time battery is drained everything is reset.
Jul 15, 2023 at 3:26 AM
Avatar
STRAILER
  • Experienced Mechanic
  • 55,249 POSTS
Sorry we only handle one problem per thread, please post your new question here, you must be logged in.

https://www.2carpros.com/questions/new

Cheers, Ken
Jul 16, 2023 at 2:51 AM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.