Seemingly Random Electrical Issues?

Tiny
DSCHWINDT
  • MEMBER
  • 2006 BUICK LUCERNE
  • 3.7L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 123,000 MILES
Just recently my car has been doing the following, but only on occasion:

1. When I turn the key to the ON position, the normal functions activate as expected, but when I turn the key to start the car, nothing happens. No sound, no attempt to start, nothing.
2. While the key is in the ON position but the car is unable to start, three warning lights appear on the dash. The anti-slip/hydroplane light, the ABS light, and the red 'BRAKE' light.
3. Then, after I try starting the car a few times, eventually the car reacts to me turning the key and the car starts. I do not know why the car won't start sometimes and sometimes it does. I don't change anything that I am aware of.
4. However, when the car starts, the three dash lights mentioned earlier are still on, the vents blow air but the A/C doesn't work, and the gear indicator on the dashboard (PRND) does not respond to me shifting gears. So, I am able to shift to reverse or drive and the transmission functions correctly, but the lights on the dashboard do not reflect this change. The gear indicator remains on 'Park'.
5. Then, if I begin to drive the vehicle with all the aforementioned problems, soon I get a dashboard warning saying 'Service Brake Assist'
6. Soon after the 'Service Brake Assist' light goes away, then the following things occur:
- The door locks engage
- The A/C begins working
- The dash lights go away
- The gear indicator updates and correctly shows which gear the vehicle is in

Then the vehicle drives normally for the duration of the trip. However, the next time I start the car, the same problem may or may not recur. Are you able to help me with this problem?
Sunday, July 20th, 2025 AT 8:20 PM

31 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Yep, it sounds like there is a problem in the CAN, either the PCM or BCM is going out, either way you need to do a CAN scan which this video can show you how, then we can gather the codes and go from there:

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

Also, you might want to try and do a hard computer system reboot, this guide can help with that:

https://www.2carpros.com/articles/step-by-step-guide-performing-a-hard-system-reboot-for-your-vehicles-electronics-systems

This can be the internal mode switch inside the transmission can be going bad and shorting out which may affect these other systems. Please go over these guides and get back to us.
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Monday, July 21st, 2025 AT 1:37 PM
Tiny
DSCHWINDT
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So I bought a Launch scanner and scanned my car. I couldn’t find anything about a PCM or BCM showing errors. I’ve attached a photo of the scanner details. However, I did perform a hard computer reboot before I scanned. Is it possible the hard reboot fixed everything? I haven’t driven the car yet to verify, but I’m wondering if that’s even possible.
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Thursday, July 31st, 2025 AT 4:51 PM
Tiny
KEN L
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  • 54,137 POSTS
Hmm, the hard reboot could have fixed, it I would drive the car to see what happens.
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Friday, August 1st, 2025 AT 8:47 AM
Tiny
DSCHWINDT
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I’ve driven the car about 6 separate times by now, and there haven’t been any more electrical issues.
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Saturday, August 2nd, 2025 AT 12:20 PM
Tiny
KEN L
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Yes! The reboot to the rescue! Thanks for letting us know, we are here to help, please use 2CarPros anytime.
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Sunday, August 3rd, 2025 AT 11:19 AM
Tiny
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Well, that didn’t last long. The electrical errors have returned and they are worse than ever. Currently, the car won’t start and the CAN scanner cannot connect to the vehicle. I am getting the following error when running the diagnostics.
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Wednesday, August 6th, 2025 AT 5:29 PM
Tiny
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I just rebooted the car again, but nothing has changed. Still won’t start.
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Wednesday, August 6th, 2025 AT 6:27 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
This is common when the BCM goes out. I would, search ebay to find a preprogrammed unit you can swap it out with. Here is the location. Check out the images (below). Let us know how it goes
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Thursday, August 7th, 2025 AT 6:18 PM
Tiny
DSCHWINDT
  • MEMBER
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I replaced the BCM, but that has not solved the problem. I also rebooted the computer after it was installed. Today while driving, I noticed the tachometer and speedometer froze at a certain point so that my RPMs were 1900 and my speed was 39 when I was stopped at a red light. However, all the aforementioned errors and these new ones are intermittent. They happen on and off as I drive, and when I got home my car wouldn’t start again.
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Monday, August 18th, 2025 AT 6:56 PM
Tiny
KEN L
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I am sorry, with this new information it looks like the PCM is going out. With a more high end scanner it might have picked that up, the problem is when you reboot the car the computer works okay until it heats up. Here is the location of the PCM. You will need to remove the air filter housing to get to it. Check out the images (below). Please let us know what happens.
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Monday, August 18th, 2025 AT 7:24 PM
Tiny
DSCHWINDT
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I replaced the PCM, and the same thing is happening. I haven’t rebooted the computer since replacing the PCM. I plan to do that later when I have time, but just keeping you updated. Let me know if you have any input.
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Monday, September 1st, 2025 AT 10:45 AM
Tiny
KEN L
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Does the canner still not connect?
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Tuesday, September 2nd, 2025 AT 7:28 PM
Tiny
DSCHWINDT
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The first image shows the final screen before it switches to the second photo. Is that showing that it connects or no?

Also, are you thinking the PCM replacement changed anything? I get free returns, so just seeing if I should return it or not.
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Sunday, September 7th, 2025 AT 4:12 PM
Tiny
KEN L
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Yep, there are no codes in the ECU, but I don't think that is a CAN scanner. Also, we might be barking up the wrong tree, it can be the ignition switch. Lets get a CAN scan done

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

and here is a guide to help check for power output of the ignition switch, test for power at the white, pink and brown wire with the key on. Here is the guide and the switch location.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the images (below). Please let us know what happens.
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Monday, September 8th, 2025 AT 10:45 AM
Tiny
DSCHWINDT
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Okay, I will look into those things. As the issues are intermittent, do I need to wait until the car is exhibiting the issues before testing for power at the ignition switch?
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Monday, September 8th, 2025 AT 11:01 AM
Tiny
KEN L
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Yes, when it is failing is best to run the test. Great question :)
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Monday, September 8th, 2025 AT 11:25 AM
Tiny
DSCHWINDT
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https://www.amazon.com/dp/B073GW5MTS?ref=ppx_yo2ov_dt_b_fed_asin_title

This is the scanner that I own. Is this not the same one in the link of the YT video you sent? It looks the same to me.

Also, I got the image of the ignition switch location. You mentioned a 'guide'. Did you intend to send a guide as well?
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Monday, September 8th, 2025 AT 4:18 PM
Tiny
KEN L
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Yep, I forgot to add the guide which is:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

I went over the scanner you have and it does not scan the CAN system which included the BCM and HVAC systems. I would check the ignition first and if it is not he problem go for the CAN scan.

This is the next level up scanner the does the BCM for $169.00

https://amzn.to/3I7T9nk

Let us know how it goes.
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Monday, September 8th, 2025 AT 5:12 PM
Tiny
DSCHWINDT
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Okay, well I purchased the scanner that was linked in the YT video, so I’m stuck with this one now. Not sure I want to pay for another scanner.

Also, now that we’re considering the ignition switch, perhaps I should mention another thing my car does. My car routinely thinks the key is in the ignition when it is not. When I pull out the key and open the door, the door chimes as if the key is in the ignition. Usually, if I put the key back in and jiggle it a couple times the chime stops. Does this make you think the ignition switch is faulty?
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Tuesday, September 9th, 2025 AT 4:13 PM
Tiny
DSCHWINDT
  • MEMBER
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Here is the ignition switch. The guide you sent shows how to use a test light (which I have), but it didn’t say anything about how to use it for my situation. I assume different wires should be receiving power depending on what position the key is in. How can I use the test light to verify my problem?

Thank you for your continued assistance.
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Tuesday, September 9th, 2025 AT 5:12 PM

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