JudyAA

Parasitic Battery Drain - FIXED!

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After months of parasitic battery drain, I was told by my mechanic, a former Lexus mechanic, that the multiplex body control module is what's causing the drain. The car has 157K miles and I hadn't planned on doing another repair before selling it. Where is this part located, what labor has to be done to replace it, and is it possible to get a refurbished one that will work with my existing key? My mechanic says it's possible this is related to an accident in which the headlight was replaced, so the case is being reopened with the insurance company. Since the servo motor is also going bad, should I just trade in the car?

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I just had my bumper replaced and now I am experiencing battery drain issues. I am curious if this might be somewhat related?

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We've got the same problem with our 2008 IS250. 

The battery and alternator are fine, so we had an electric specialist come and have a look. We learned that there's a parasitic drain from the onboard body control module which is discharging the vehicle when it's switched off. The body control module also powers the audio module which is another item that can sometimes have this parasitic drain problem. 

Either way it needs repairing or replacing and 'regular' garages don't seem to have the software or coding skills needed to fix it. So it will have to go to Lexus & that's going to cost a lot! 😞

Has anyone managed to remedy the problem? If so, how and how much did it cost?

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I should have posted the final resolution to the repair while I still owned the 2004 Lexus. I took it to the dealership and they admitted that they were scratching their heads trying to identify the source of the parasitic battery drain. They eventually identified it. It was the driver seat lumbar support! I opted to have it disconnected rather than fixing it, and that took care of the problem.

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I didn't know that lumbar support would cause a drain. 

Isn't it 'just padding'? 

---

We had the car about 4 years and it wasn't an issue before. 

The drain was so 'strong' that a new battery was reduced to 43% of its life within 2 months. 

Not using the car for a day or more resulted in the battery being so flat that we couldn't even lock the car with the button on the key, but had to do so manually. 

We have now sold the car. We got less for it because we declared the fault but that's only fair. 🙂

 

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Most likely, the lumbar support is an inflatable bladder that requires compressed air from a compressor. It could be that the compressor had shorted, causing the drain.

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Our drain wasn't caused by the lumbar support. 

The diagnostic report showed there was a parasitic drain from the onboard body control module which was discharging the vehicle when it's switched off. Alternatively, it could have been the body control module also powers the audio module which is another item that can sometimes have this parasitic drain problem. 

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