Battery light on at startup after curious RPM dip (below normal levels)
Thread Starter
|
Senior Member
Joined: Feb 2013
Posts: 397
Likes: 43
From: Hamilton, ON, Canada
Battery light on at startup after curious RPM dip (below normal levels)
So guys I have a very weird issue with my 2009 XF. After a spark plug change, every time I start my car after about 30 seconds the battery light comes on. After that the car runs perfectly.
Heres my notes on the issue:
Rpms perfect while driving. No issues at all
Upon startup the rpms dip and then go back to normal. This is what triggers the battery light
Before the rpms dip after startup, everything works. Heated steering wheel, heated seats and cooled seats. I can hear the fans and they are working perfectly.
As soon as the rpm dip triggers the charging light, nothing works. Heated and cooled seats stop working. Fans in the seats shut down.
Climate control and 12v adapter are working the entire time.
So about 30 seconds after startup I get an unusual dip in rpm and then it goes back up to normal. A few seconds later the battery light comes on and my heated/cooled seats and steering wheel stop working.
My mechanic ran the codes and he was getting a battery monitoring module code. So he changed the bms/negative battery terminal and then the car started to throw the same code PLUS a P0620 I believe which relates to a loose connection or alternator or perhaps a few other issues.
He also replaced the battery and problem still persists. He says the battery and alternator are both charging fine. Alternator was replaced with a new unit 8 months ago and has 8k km on it.
His next thought is a faulty alternator but based on my observations above I’m not sure. Could it be a fusable link of some sort? The rpm dip at startup is the root problem of this entire thing I feel. Once that happens I get the battery light and lose power to multiple options in the car.
Any assistance would be greatly appreciated. Thanks.
Heres my notes on the issue:
Rpms perfect while driving. No issues at all
Upon startup the rpms dip and then go back to normal. This is what triggers the battery light
Before the rpms dip after startup, everything works. Heated steering wheel, heated seats and cooled seats. I can hear the fans and they are working perfectly.
As soon as the rpm dip triggers the charging light, nothing works. Heated and cooled seats stop working. Fans in the seats shut down.
Climate control and 12v adapter are working the entire time.
So about 30 seconds after startup I get an unusual dip in rpm and then it goes back up to normal. A few seconds later the battery light comes on and my heated/cooled seats and steering wheel stop working.
My mechanic ran the codes and he was getting a battery monitoring module code. So he changed the bms/negative battery terminal and then the car started to throw the same code PLUS a P0620 I believe which relates to a loose connection or alternator or perhaps a few other issues.
He also replaced the battery and problem still persists. He says the battery and alternator are both charging fine. Alternator was replaced with a new unit 8 months ago and has 8k km on it.
His next thought is a faulty alternator but based on my observations above I’m not sure. Could it be a fusable link of some sort? The rpm dip at startup is the root problem of this entire thing I feel. Once that happens I get the battery light and lose power to multiple options in the car.
Any assistance would be greatly appreciated. Thanks.
Last edited by nasa25; Feb 18, 2018 at 09:26 AM.
Thread Starter
|
Senior Member
Joined: Feb 2013
Posts: 397
Likes: 43
From: Hamilton, ON, Canada
After speaking to people the theory is that something is drawing a ridiculous amount of power at the point where the rpms drop on startup.
Pulling high draw fuses and retesting will hopefully find the culprit.
Pulling high draw fuses and retesting will hopefully find the culprit.
Junior Member
Joined: Dec 2019
Posts: 1
Likes: 0
Did you manage to sort it out? I have the same RPM drama but on mine it does it while braking to a stop, but no red battery icon, just dips RPM and slight vibration, also totally random, once every 10-15 stops.
Thanks
Junior Member
Joined: Feb 2023
Posts: 5
Likes: 0
Vacuum leak
vacuum leak
Senior Member
Joined: Feb 2018
Posts: 272
Likes: 56
From: UAE
OP posted resolution later in other threads, which is nice.
New alternator is most likely in your future
This also happened to me recently and it wound up being my rear junction box. They needed to reprogram it. Spent $2k chasing that problem changing tons of stuff before getting to the root of the cause.
But its more than likely your alternator
This also happened to me recently and it wound up being my rear junction box. They needed to reprogram it. Spent $2k chasing that problem changing tons of stuff before getting to the root of the cause.
But its more than likely your alternator
I had a charging light that was plaguing me for almost 2 months last winter
changed an almost new alternator - no change
changed battery and bms module (that is part of the postive battery terminal) - no change
finally tracked it down to a software error in my rear junction box. Dealer reflashed the software and it’s been fine since. If you’re scratching your head with this charging light, suspect the rear junction box (located at the side of the trunk) after you’ve eliminated everything else.
changed an almost new alternator - no change
changed battery and bms module (that is part of the postive battery terminal) - no change
finally tracked it down to a software error in my rear junction box. Dealer reflashed the software and it’s been fine since. If you’re scratching your head with this charging light, suspect the rear junction box (located at the side of the trunk) after you’ve eliminated everything else.
Thread Starter
|
Senior Member
Joined: Feb 2013
Posts: 397
Likes: 43
From: Hamilton, ON, Canada
I forgot to add that I actually tried to replace the junction box and the dealer couldn’t get it coded correctly….so they just reflashed my existing box.
whenever you’re chasing a ghost seems like it’s always software related.
Thread
Thread Starter
Forum
Replies
Last Post
dmsdvls3
X-Type ( X400 )
18
Oct 20, 2010 06:09 AM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)