Hey guys, I don't spend much time here because my wife's TL has been a great machine, but now that the mileage is adding up, I've got some questions about the issues I'm seeing.

'04 TL with Nav
108,000 miles
Regular maintenance performed for the most part

Got a B4 code recently and thought it was time for a new timing belt. Shop diagnosed it as two different O2 sensors (B1S1 and P0155). Doubting they would both go out like that, they tried replacing the relay they share as a first step.

Two weeks later, car is having electrical problems. Won't start. Seems like a bad battery. I open it up and the battery terminals are super corroded. I clean them with baking soda and make sure there's good contact. Jump start. Drive around for the day. Problem seems solved.

Next day, car won't start. Battery's dead. I never saw the charging light, so I assume the alternator's probably fine, right? Probably just needs a new battery (I was unable to find a date on the battery that's in there).

I'll do some tests with the multimeter when wife gets home to jump start it for me.

My questions:
1) This is probably just an old, shot battery, right? The car ran fine for an hour, sat for 4 hours, started up and ran fine back home. Sat overnight and power was too low to crank.

2) If the shop replaced an O2 sensor relay, they should have disconnected the battery, right? Judging by the pile of white corrosion and seized connector bolts, there's no way that battery has been out recently. Is it possible that they did something to cause a short or anything that would result in accelerated corrosion at the battery terminals like that? Or even worse, that they did nothing and charged me for a new relay?

Once I get the electricals squared away, then I'll take it back in for the timing belt service. Can't wait for that one ($1160 including water pump, plugs, oil, and rotation).

 

sounds like a battery for sure. our car's do some funny things once the batter starts to fail.