Brake light

I am not familiar with the 2005. Does it have LEDs for the brake lights at the top and a small bulb for the tail light at the bottom?

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The brake light (or stop light) in Gen 2 is LEDs that are built into the rear light housing, and not (easily) replaceable. Whatever bulbs you have been replacing have not changed the stop light issue, because they weren't stop light bulbs.



If all of the LEDs on that side are uniformly dim, there might be some simple and fixable electrical issue on that side. It probably isn't just a matter of age, assuming the ones on the driver side that work great are the same age.

I would probably look for something simple before moving toward replacement. Toyota would just replace that light assembly, but there have been threads here with people taking it apart.

 

Most likely a bad ground so that the bulb in that position does not see the full battery voltage. (This is a really common problem on headlights.) Also possible there is something wrong with the 12V lead which is restricting the current. What I would do is probe the good (driver's) side on each side of the bulb (with somebody else stepping on the brake) using a voltmeter, with the negative lead to a good chassis ground, and note the voltages. Then try the same thing on the bad (passenger's) side.

For instance, you might measure 12V and .1V on the good bulb, but 12V and 3V on the bad one. That would be a bad ground. You could verify that by using a bit of wire to connect the ground side to a bit of chassis metal - the bulb should get brighter. To fix trace the ground wire back to an actual ground, and clean it up. That usually means unbolting it from the chassis, cleaning it, and rebolting it. Typically this path will not be too long. If this was the issue I would also expect that some of the other bulbs on that side would appear dimmer, like the turn signal, or the "headlight on".

If you measure 10V and .1V on the bad side the battery side of the circuit is bad. This would be a more challenging problem, as you will need to trace the positive voltage wire conceivably all the way back to whatever computer is driving it. In this instance the other bulbs on that side would probably be as bright as they should be.

It is also possible that the socket connections for that bulb are dirty or corroded, in which case you might see 12V and .05V, or something like that, because in effect there is a resistor in series with the bulb inside the socket. If this is the issue some of the metal contact in the socket will probably not be shiny. Try some contact cleaner, and/or a bit of very fine sand paper to remove the contamination.

If you do not already own one, a good enough voltmeter can be had at Harbor Freight for not much, probably less than $10.