2003 Battery Draining - Toyota Nation Forum : Toyota Car and Truck Forums

Thurmont · 04-10-2005, 08:26 AM

I have a 2003 Tundra and since 11/04 I have had problems with the battery going dead over night. Doesn't happen evey night and sometimes goes for 3 or 4 weeks before going dead. Dealer replaced the battery in 2/05 and problems still here. The dealer can not find anything wrong, but don't know how much they are checking either. Had the truck 3 days last week and came up with nothing wrong. Thinking back the problem stated shortly after I used a trailer and I have heard that there is a problem in the trailer wiring harnass that could cause this. Does anyone know what relays I can remove to disable the trailer wireing. I don't use a trailer but once in a blue moon and could reinstall the relay and or fuse when I need it.

Thurmont · 04-10-2005, 03:56 PM

I think I may have found the problem. On my truck if you have the head lights on and cut the engine off it will cut the headlights off however I found the trailer lights relay will remain engerized until you turn the headlight switch off. I think the relay being engerized all the time is cause the battery to go dead. I am monitoring the battery voltage with the relay engerized and see if the voltage drops below 12 volts before I pull the relay. Does anyone know if the service bulletin about the trailer wiring states anything about correcting this problem.

toto · 04-10-2005, 05:29 PM

Not sure if you mean TSIB AX006-02 ("Trailer Wire Harness") or not... that one's just a general notice that there are in-line fuses in the trailer wiring harness. Starting in 2000, they added the in-line fuses in addition to the vehicle fuses, so if they suspect a fuse problem, they need to look in two places.

Thurmont · 04-10-2005, 06:01 PM

I thank you for your reply. I have TBS number EL015-03 Electrical -Trailer
Tow Relay remains energized.
UPDATE!!!!
Talked to the dealer this morning and told the service manager about the TSB EL015-03 and he checked and what do you know there is a problem. He said they have to add another relay to make sure the towing wiring relay deengerizes when in the headlights are in the auto turn off mode.

Thurmont · 04-11-2005, 02:26 PM

UPDATE ON BATTERY DRAIN!!!!

I talked to the dealer service manager this morning and told him about the TSB EL015-03 and he called me back to make an appointment to repair the truck. Wouldn't you know that there is a problem with the trailer wiring relay and they have to add yet another relay to make sure the tow relay deenergizes when the headlights are in the auto off mode. Seems I am the only person in the USA that has this problem. He has never heard of it before , yet there is a bulletin out about the very same thing. Go figure.