Service Tips

[LocDog]

So0o I'm readin Popular Mechanics (Nov 03) and i stumble onto a column titled "service tips".Out of four irrelavant tips one of them stated:"Discharge the battery by leaving the dome light on in your '03 Corollaor Matrix? And now the daytime running lights dont come on at all?Toyota has a revised DRL relay to replace the one prone to damagefrom deeply discharged batteries. Technical Service Bulletin EL001-3"Is this of use to anyone?

[joatmon]

Interesting.I looked at the healight wiring diagramTHere is the headlight control on the steering column, the DRL module, a headlight realy and a "DIM" relay. The headlight relay is the one that puts power to the headlights, so if that one dies, then you have no headlights at all, ever. I wasn't sure about the DIM relay, so I took mine out, and if the DIM realy doesn't work (or is not there) then you get no high beams. There does not appear to be a "DRL Relay" unless it is a part of the DRL module.This leaves me to conclude from the article that deeply discharging the battery can cause damage to some DRL modules. The headlight wiring in the car is dependent on the DRL module, so I would not try to damage my DRL module on purpose by deeply discharging the battery. THere are already ways to disable DRLs. However, if someone does drain the battery and then has DRL or headlight problems, it may be that something in the DRL module failed. Also, if anyone does a deep discharge on the battery for whatever reason, it would be a good idea to verify that the headlights works as desired before relying on them either to see or to be seen out on the road.Good find!