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Porsche TSB WMJ9
Make:PorscheNumber:WMJ9Title:Reprogramming control unit gateway (battery sensor)Date:6/13/2022Models:
2018-2021 Cayenne
2019-2021 Cayenne S
Summary Due to a software error in the battery sensor, there is a possibility that the aging status of the 12V battery may be calculated incorrectly. As a result, a premature replacement of the 12V battery may be recommended. To prevent this, the battery sensor in the affected vehicles must be re-programmed. Please arrange for this measure to be carried out as soon as possible on affected vehicles. As of the time of this posting, the repair is immediately available.
Last edited by FlyPenFly; Aug 19, 2023 at 04:49 AM.
So, those people with the battery error message do not need a new battery, but just need to have their controller/sensor software reprogrammed.
I hope those people with these battery false error messages/issues weren't suckered by their dealers to pay $1000's of dollars for a new battery.
I see how and why the 3rd party companies repairing the LiFePO4 batteries were changing the controller/sensor and reprogramming it.
first time the yellow warning light the dealer does the software update....next time it appears the only solution is a new battery, which is exactly what happened to me
Clearly this is just part of a planned obsolescence campaign for the battery to force folks to replace them out of warranty. In the case of the recall it seems that the bug is causing it to go off during the warranty period which is the opposite of what Porsche wants.
Clearly this is just part of a planned obsolescence campaign for the battery to force folks to replace them out of warranty. In the case of the recall it seems that the bug is causing it to go off during the warranty period which is the opposite of what Porsche wants.
Well I'm at a crossroads about the whole car with this one...
I have a base with all the options, love the car. I have about 3k miles to decide if I want to keep the car and buy the Fidelity warranty which gives me 100k miles / 7 years of bumper to bumper coverage (except the battery lol) or trade it in for another car.
I just DO NOT want to pay $1,000 / year for a battery in case this stupid thing fails again and you just have to keep swapping it out every 4 years for $4k.
Yesterday morning, my 2019 Cayenne with 10k miles, delivered new in December of 2018 popped up the “Battery Low Service Necessary” light.
I have read most of this forum thread. Lots of data, thank you.
I drove to a family thing about 30 minutes of highway driving, two hours later, started no problem, drove 30 min home.
With my voltmeter, I checked voltage last night and this morning on the posts under the hood. Both times voltage was 13.5v.
I pulled out my LiFePO4 capable battery charger and hooked it up to the posts under the hood. Within 10 minutes, the charger was indicating a fully charged battery, so I really don’t think I have a battery problem.
I printed out the Porsche Factory bulletins on this thread, including the one about the software upgrade.
Questions - Is there a way for me at home to clear the yellow warning indication of “Battery Low Service Necessary?”. Maybe by disconnecting both the LiFeP04 starting battery and the battery in the cargo area?
If not, is my next step to contact Porsche service about software upgrade?
thanks!
Yesterday morning, my 2019 Cayenne with 10k miles, delivered new in December of 2018 popped up the “Battery Low Service Necessary” light.
I have read most of this forum thread. Lots of data, thank you.
I drove to a family thing about 30 minutes of highway driving, two hours later, started no problem, drove 30 min home.
With my voltmeter, I checked voltage last night and this morning on the posts under the hood. Both times voltage was 13.5v.
I pulled out my LiFePO4 capable battery charger and hooked it up to the posts under the hood. Within 10 minutes, the charger was indicating a fully charged battery, so I really don’t think I have a battery problem.
I printed out the Porsche Factory bulletins on this thread, including the one about the software upgrade.
Questions - Is there a way for me at home to clear the yellow warning indication of “Battery Low Service Necessary?”. Maybe by disconnecting both the LiFeP04 starting battery and the battery in the cargo area?
If not, is my next step to contact Porsche service about software upgrade?
thanks!
The iCarsoft CR Max would probably clear that fault. I can't say for certain because I don't have that fault. But last night I did clear old stored faults in my car using the iCarsoft CR Max. It's a good diagnostic unit. Other OBD devices would probably clear the fault, but you would need to do some research on this.
Hi LSR,
Just wondering if you can describe step-wise how you reached to the battery compartment under the passenger footwell in the vehicle?
Is it as simple as removing 2 visible bolts in the passenger footwell? Thanks in advance.
PS: I don't own a Cayenne and looking for instructions how to gain access to the footwell to take a peek at the battery type myself, before any vehicle purchase.
At the moment, I am looking at the used car market in hope to find one with an AGM battery installed, I was hoping perhaps some 2020 Cayenne models may already have AGM instead of LiFePO4 batteries. (Anyone know?)
Originally Posted by LSR
Reading all of these horror story posts about lithium batteries got me to wondering about the AGM battery in my 2022 base Cayenne. Is it essentially off-the-shelf and otherwise ordinary? Or, does a Cayenne AGM battery also have specialized internal circuitry like the lithium battery that will be costly to replace? Anyone know?
Last edited by mxp0; Aug 21, 2023 at 01:46 PM.
Reason: minor
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