LeX2K

What would you like to know? A relay is not going to make any difference because when the car is off no relay is active. If you think the stereo is drawing too much power then you can either replace it with another factory system or get something else.

Did you try only unplugging the stereo to narrow down the problem?

05lex330

Thanks for that information. I would like to know where the relay is that controls the radio. I have not tried unplugging the radio but that is a good suggestion. I pulled the fuse and the draw went away but unplugging the actual radio will pinpoint the problem exactly. I was just wondering if this was something I could fix or if I had to get a new (junkyard) unit.

A bad relay cannot cause parasitic draw? According to this website it can:

http://www.ehow.com/list_7326280_com...ery-drain.html

"Relay switches that are stuck in the "on" position can also cause a battery to drain."

LeX2K

I was talking about a relay in respect to the stereo, which is what you asked about. The stereo gets constant power and switched through the ignition. You can start pulling relays if you want it won't hurt anything, but generally on these cars the relay contacts don't weld themselves. It is possible of course.

PFB

Except for the radio, what else does the fuse that you pulled out control?

gveach

Had a similar drain once on my early LS model. Resulted in a dead battery after setting for several days. Finally after months of head scratching found the problem, a bad lamp switch on the passenger side visor mirror. Visor was always closed so you couldn't see the light. Thanked my wife for finding the problem. In fact visor was quite hot, could have become major problem.

05lex330

According to the PDF's I am reading the RAD. no 1 circuit controls the car audio system/ navigation system. I guess I need a new radio

PFB

The next logical thing to do is unplug the radio, reinsert the fuse and measure the current draw. If it's the radio, then it should be 0 ma. If not, than the problem lies elsewhere, or that fuse controls something else as well

BTW, you should always wait at least 5 minutes before measuring any parasitic drains.

Phil

ES300NZ

ok, cars always drain current from batterys (modern ones), from the ECU-B or ECU-A fuse, this is because the ecu has a memory system, and that requires battery power to keep.

and modern radios have a memory system which remembers your music sound preferences (bass/treble), so that also uses power.

The drain is so small, you can measure it, but all up it would under an amp in total.

PFB

Of course you're right, but I guess my reply was confusing.

What I meant to say is that once the radio is removed, the drain on that circuit only should be 0 ma. Again assuming that the OP is correct in stating that that fuse only controls the Radio.

Sorry if I caused some confusion

Phil

ES300NZ

yeah I thought you meant that, read it twice, wasn't quite sure

PFB

One more thought.I believe, but am not sure, that your car has a power antenna. If so, make sure it's not stuck, and that it does work properly.

Try disconnecting it and taking your previous measurements again.

Phil

Mphidd

Ok guys I've been having this issue with my 99 Lexus ES and just found something out today. My partner suggested that maybe the alarm system on the car could be the cause of my battery dying which at first didn't make sense but then I experienced it first hand...........I've been using a key to lock and unlock the car since I do t have a remote and noticed today that when I shut the car off and hit the central lock button in the car, the car kept clicking and trying to lock but couldn't. I'm going to have a remote ordered and programmed next week so I can update you guys but just a thought

Emuller

I have a short that drains my car battery when vehicle is left for short durations. I did a parasitic check of battery by hooking up an amp meter on negative lead, and ecu-b fuse was the culprit. I drove car w/out the fuse installed. Have lost door lock w/ fob, clock memory, window switch memory, etc. any ideas on the best way to narrow down the offending circuit that is drawing my battery down? With fuse in, there is a 8.7 amp draw, w/ ecu-b fuse pulled, draw goes down to .337, which appears to be normal. I have replaced battery, alternator, and starter on car. The dealership failed to find this problem, and I don't want to put anymore dealership reps kids thru college. Any help would be appreciated.

ES300NZ

the ecu draws current to hold memory. that current drain is a tad high to be honest but I would expect to see some drain on that fuse. Perhaps the ECU isn't turning off.

Don't be too quick to say 'short' and 'drain'. In fact it might be some system remaining on. A 9 amp drain would take quite a while to drain a good battery, perhaps overnight. (e.g. high remark).

if the fuse is left out does the battery hold it's charge overnight or for a few days ? because if it does then the issue on that circuit.

ECU-B (from memory), is the power to the ecu which keeps the memory (self learning ecu) alive. you can safely remove it permanently if you don't want to do a repair. You fuel economy will suffer slightly (quite slightly), and the car will be strange to drive each time you start it up, but within 5mins it will learn enough to be fine.

Emuller

Thanks for the response.

The 7.5 amp fuse was pulled and left out the last 24 hours. Car battery held it's charge, and motor starts fine, but many features are inoperative. IE locking door w/ fob, door lock switch on door , air conditioning settings, window switches to name a few.

The issue is definitely the circuit. My problem now is how to isolate the problem item on that circuit. I ordered a haynes repair manual, so this may cover a in depth repair, or at least an accounting of all the items impacted by the ECU-B. Is there a way to disable each of the users of this circuit?