new battery prolem Options

[Cormudgen]

Ok, so my battery light went on sometime last week. I went to autozone and they test my alternator and my battery. verdict is that the battery is weak(bad cell maybe) but the alternator is fine. ok, i go to wal mart and buy a new battery. (the 29.99) "Autostart" battery. put it in and the light continuse to stay on. drive around a lil and it is still on. i decide to drive to autozone again and get them to test it. the battery and alternator both read good this time. he mentions that i may need 15 min to clear my ecu for the light to go off or i cuold simply drive around for a little while. i then drive around for 20 more min and park it. take the postive off my battery for about 20 min. put it back on, and the light is still on. anyways i'm home now and the postive terminal is off, going to attempt to let it sit overnight. any suggestions?

thanks
cormudgen

[macavely]

you should have left your battery hooked up... they light might come back on... and if they light comes back one just drive for a good 20 minutes and turn the car off.. wait about another minute then turn the car back on the light should be off...

[Cormudgen]

i drove for more than 20 min turnend the car on and off many times and the light was still on. it wasn't until after that that i tried disconecting the positie terminal.

cormudgen

[macavely]

are your connectors clean?

[96stcoupe]

Some places have crappy testing equipment. I know the tester where I work is garbage. Anyway, use a volt meter and test for around 14.4V at the alternator.

[Cormudgen]

it has been tested at 2 places... just for backup reasurance

[boosted_K2]

you may just trie resetting the ECU.

[Cormudgen]

[Cormudgen]

ok, my positive terminal was left off over 14 hours and no luck. i then tried pullin both the ecu and efi fuses for about 20 min to no avail. i called toyota and they said that resetting the ecu wouldnt help the light being on anyways. but they would LOOK at it for $43 and then decide what needs to be done....

cormudgen

[Mynzeyes]

take the gauge cluster out and take the battery light out of the back of it. .

but seriously, that's really weird...but as long as your CEL isn't on, you should be good to go..

[Cormudgen]

[Mynzeyes]

CEL == Check Engine Light

[Cormudgen]

[GeEkBoY]

The battery light comes on when the alternator is not charging. If your car is not running, but the key is switched on, the battery light will be on. The threshold for the light is somewhere between the 14.7 the altenator produces and the 12 that the battery puts out. They do this so you will have warning before your battery is dead.

It sounds like your altenator may be starting to go or the sensor is toast:
How many miles since the altenator was replaced?
Was the voltage on the altenator checked on the car, or bench tested?

If the alt. was bench tested, that is done at no load, when you load a marginal altenator, the voltage output drops and that could cause the problem. The best way to test it is with a voltmeter on the car while it is runnuing like 96STcoupe suggested.

[Cormudgen]

yes, it was tested on the car and read to be fine. do you konw where the sensor is located and i would check to see if it was bad? lastly would doing a diagnostics test thru the OBDII be of any help?

[KAMiX]

If you disconnect the positive terminal and then step on the brakes it will "reset" the ECU. But as you said this isn't going to fix it by the sounds of it.

[GeEkBoY]

If you can get your hands on a wiring diagram you may be able to find it. I am not sure where the sensor is. OBDII may help, but you need a technician who understands the systems. There is a ton of data in those things that most mechanics don't understand. I always prefer a guage over an idiot light, then you would have a better idea of what was really going on.