2002 Buick regal intermittent headlight pulsing

[mikeytcarter]

Hello everyone!

i have recently acquired a 2002 Buick Regal. This car was a one owner car and I picked it up in October with 74k miles on it. It has been very well taken care of. I bought this car because of the reliability factor, however I have fallen in love with how it drives! The only issue that I am having is intermittent headlight pulsing. It only happens when the car is decelerating and slowing down under 30mph or so. So far I have replaced the battery, had the alternator tested(tested good ), went and bought another alternator and installed just in case of possible voltage regulator. Also found and cleaned thee grounds under the fuse box, next to the drivers headlight, and the engine ground by the exhaust. I have also ran a big 3 wire upgrade (did this for future sound system) as well as an extra power wire from fuse box to alternator(saw some videos where people said this extra line helped)This seemed to make my headlights a bit brighter, but not affect on the pulsing. All that being said i am still getting the same result. The interior lights will dim for a moment when the car first starts and the the headlights on deceleration. From what I have found there is no headlight relay, only fuses. I have one friend who has suggested new bulbs, however I am not convinced this would fix anything as they are older but still light up well. Any suggestions on where to look next would be greatly appreciated! 

[mikeytcarter]

 

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Edited 3 hours ago by mikeytcarter

[mikeytcarter]

[Black92GS]

You'll have to define the pulsing.  Is it like a continuous flicker, or is it more along the lines of a large draw where the lights briefly dim once and then come back up?

[mikeytcarter]

The latter would be a better description. It’s like a large draw and they will dim then go back to normal. Sometimes it does it once’s, sometimes a few times in a row 

[Black92GS]

2 minutes ago, mikeytcarter said:

The latter would be a better description. It’s like a large draw and they will dim then go back to normal. Sometimes it does it once’s, sometimes a few times in a row 

Ok.  Now this may sound like a really weird question....are you absolutely positive that the ABS isn't activating when you're slowing down? The ABS pump activates briefly during its self check shortly after startup (or when you first start moving...can't recall which). In every 90s/2000s GM i've driven, including a 2000 Regal, the ABS pump initially kicking in would often cause a bit of a power dip (headlights dimming slightly, blower speed audibly slowing slightly etc..). Something that I have also had issues with in some of those vehicles has been unwanted ABS activation from weak/failing wheel speed sensors and/or failing tone rings. 

You may need to really listen and feel for an unwanted ABS activation, as it can range from being a very quick and random engagement of the pump that you don't really feel.... to full on constant ABS activation with the pushback of the pedal and the sensation of a loss of braking power. 

[mikeytcarter]

Hmm I am not positive but that does seem to make sense given when its happening. Im not necessarily on the brakes when it happens, but sometimes just letting off the accelerator causes it. I have an Autel scanner. Would there be a way for me to watch for this using live data in some way? 

[mikeytcarter]

Also just remembered when I first picked the car up one morning the ABS light did come on. All I did was shut the car off and it went away. Definitely think youre onto something now 

[Black92GS]

25 minutes ago, mikeytcarter said:

Hmm I am not positive but that does seem to make sense given when its happening. Im not necessarily on the brakes when it happens, but sometimes just letting off the accelerator causes it. I have an Autel scanner. Would there be a way for me to watch for this using live data in some way? 

I seem to recall my Regal doing that as well sometimes. I always attributed it to a delay between an increased electrical demand and the PCM increasing the duty cycle of the alternator to compensate. If your scanner can read ABS codes, you should be able to monitor individual wheel speeds. If it's just a generic OBD2 scanner, those usually can't read ABS data. 

22 minutes ago, mikeytcarter said:

Also just remembered when I first picked the car up one morning the ABS light did come on. All I did was shut the car off and it went away. Definitely think youre onto something now 

That's how mine started.  The odd random ABS pulse, or the occasional ABS light coming on that would disappear after a restart.  Eventually, I had to pull the fuse because the ABS began activating randomly at lower speeds and made things dangerous. 

[mikeytcarter]

Ah dang, so you just run without ABS then? My scanner is bi directional so I am going to try and drive it later maybe pin point a bad wheel speed sensor 

[Black92GS]

Just now, mikeytcarter said:

Ah dang, so you just run without ABS then? My scanner is bi directional so I am going to try and drive it later maybe pin point a bad wheel speed sensor 

You don’t have to. I did because I was I was too cheap to fix it properly at the time. No ABS was far safer than unwanted activation. Sometimes, there is a bit of rust scale that builds up and lifts the sensor (rust jacking), changing the air gap and making the signal weaker and less reliable. Other times, the wheel hub begins to wear internally and can cover the sensor with metal filings, making the signal weaker. The sensors themselves can also go bad. 

If your scanner is Bidirectional, then the odds of it being able to read ABS data is pretty good. 

[mikeytcarter]

Man thank you so much for all the info! Going to dive into this tonight and see what I find. Ill post tomorrow with the results