Hi I don't have a lot of experience with cars I have a 2000 LS400 the battery keeps dying about once a year my mechanic checked for any shorts but didn't find any is there a known issue?
it also has terrible gas mileage (about 10 mpg city) any way to improve it?

Thanks,
Sam

 

Try connecting a scan tool to the obd port after engine is warmed up. What does the temp read? Maybe engine temp sensor is bad and so engine is running rich 100% of the time?
Alternator on its way out?

 

+1 with bryboy86. Check for error codes. The ECT sensor and check for split vacuum lines, these are factors in poor MPG.

Check that the alternator is properly charging the battery. No blown fuses?

 

I had that problem with mine... the alternator was over charging the battery due to a bad regulator. I'd have the tech check out the alternator output and make sure it's within spec.

 

How old is the battery?

 

I don't have a scan tool just a code reader any good ones you can recommend that are relatively cheap?

I'm going to check tomorrow its supposed to be a little warmer

 

its a new battery I've been changing it about once a year

How do I check the ECT sensor?

 

You can get a cheap Bluetooth off eBay and use it with the torque app.
The ect sensor reports a temp to the computer, the scanner just reads it. Your temp gauge may be just below half, normal but the ect sensor may think the engine is not warmed up and so adds extra fuel.
The temp sensor and temp sender for the gauge are different.

 

is there something specific I should get
link would be helpful if you can

 

you're in NY, you can borrow a scan tool from autozone/oreily's/etc... I believe.

 

oh really? I never heard of that
either way I'd like to have one on hand does look ok

 

Ok so I checked the alternator and its giving me a consistent 14.4v
No parasitic draws
I also checked the battery and its only at 12.05v and I only got it a few months ago
any other ideas?

 

Did you check the main battery grounds and cable from alter to battery? Is the batteyr showing 14.4v at idle?

 

Im not sure what that means I followed this video
yes

 

Ok so I got the scanner today and it looks like the ECT temp rises the guage on the dash was about 25% and the temp was reading 68 celcius

is that normal?
what next?