KMB

I'm stumped. I've searched throughout Club Lexus, and while I find DRL questions and problems across all models, I haven't found any leads on why, in my 2006 RX330, DRLs just don't light.

Just the facts:

• All others headlight switch functions behave exactly as expected and as per the owner's manual
• The highbeams work just fine (I understand that in the 2RX, the DRL lights are simply the highbeams running at 6V instead of 12V)
  • Sylvania 9005 halogen bulbs work perfectly as highbeams but not at all as DRLs
  • CNLM 9005 LEDs work perfectly as highbeams but not at all as DRLs (they are expressly supposed to support 6V DRL operation)
• The 7.5A DRL fuse is not blown (though I replaced it anyway).

With the engine running and the parking brake disengaged (as per the manual), DRLs simply never come on. Is there some user-selectable setting somewhere that I'm missing, as in the 3RX? Do they only light during actual daylight and I've made the mistake of only tinkering with this at night? Did I forget to sacrifice the black cockerell and shake a bloodstick at the moon?

Thanks in advance for any leads or solutions.

mnewxcv

It is possible they are disabled in the toyota techstream software used by all dealers. If a previous owner requested they be disabled, some dealers (not all) would comply with the request and disable them. There is no way that I know of to enable them without the techstream software. You can buy bootleg versions of the software on ebay and amazon, but it can be a pain to get working non your laptop.

KMB

Well, that would fit the situation I’m seeing... though it’s frustrating. I guess the good news is that it sounds like I should be able to ask a local dealership (or maybe a capable independent shop) to turn ‘em back on.

So that’ll be my next move. I’ve had DRL on every other car I’ve owned since 1997, and I do believe it improves visibility and safety. And I’d like to have some exterior lights on during the day without dimming my head unit’s screen to the point that it’s barely visible.

Thanks for the insight.

DennisMik

It is also possible that the previous owner swapped out the orange colored DRL #3 relay (SPDT) with a black colored (SPST) relay.

Or maybe they did the wiring mod to the DRL #3 relay where they cut a wire to one of the DRL #3 relay contacts.

KMB

DennisMik, I wondered about that, after finding a mention of the mod online earlier today. I know that neither of the previous two owners did that... but I don't know about the original, first owner. (Yes, I'm the fourth, and the third in my family to own it. The rest of them keep getting newer ones but also like to keep the previous ones in the family.) More likely owners #2 and #3 might have asked a dealership or shop to turn DRL off for them...

...but I'll definitely check out the state of the relays and their connections this weekend. Thanks very much for the response.

iMSQ

1. Normally DRL's don't work when you've just started the engine and transmission is in P.
2. Check the bulbs (install brand new).
3. As I remember, DRL mode can be disabled (by Dealer).

Lexuswiz

iTrader: (1)

If the relay isn't changed, it is for sure disabled within the ECU.

I did this to my RX, coded them off with Techstream. Same results as you are seeing.

KMB

LexusWiz, mnewxcv, DennisMik, thanks again for the suggestions. I'm hoping it's simply disabled by software. I now have a suitable OBD-II cable and will begin the Windows suffering this evening.

I would simply turn on the headlights, but the problem with this during the daytime is that while the gauges and nav screen stay properly lit at full brightness, my Pioneer head unit senses power over the illumination wire and dims so much that it's barely visible. Annoying for music, extremely inconvenient for CarPlay-based navigation. I *think* the DRL will come on without the Pioneer unit auto-dimming, but if it simply doesn't work like that, I may end up just installing a switch to cut off the illumination signal to the head unit at will.

RXGS

iTrader: (2)

So I know DRLs stay off when the parking brake is engaged. I also know on some aftermarket units, people have to "trick" the unit into thinking the parking brake is on, to allow them to use certain head unit functions while the car is in motion. Is there any way that the two could be related in your case?

mnewxcv

The DRLs do not come on when the parking brake is engaged at startup. As far as I know, after starting the vehicle, once you release the brake, the DRLs come on, and will stay on until the car is turned off, regardless of if you reengage the parking brake. As for the radio being related to the parking brake signal, that is mainly for playing dvds/videos or other things that the radio manufacturer deemed dangerous to do while driving. Most radio installs that require this parking brake wire be hooked up end up grounding it, which allows full functionality regardless of if brake is applied.

KMB

I love the detective work -- and I did install a "Micro Bypass" thingy, just in case I'm ever crazy enough to try to watch a movie on my head unit while driving -- but I disconnected it, and it didn't make a bit of difference.

I have the necessary TechStream software now, but am not really feeling up for hours of Windows torment tonight...

mnewxcv

do you have windows 64 bit or 32?

KMB

It will be 64-bit Windows 10.

RXGS

iTrader: (2)

Yes but he said he had an aftermarket head unit, so the whole point of to trick the car into thinking the parking brake is on to be able to use different features.

KMB

I finally got Techstream 12.x running and connecting to the car under an eval copy of Windows 10 32-bit... Dug into the settings, found the right parameter, and confirmed that the car thinks the DRLs are... already on.

Sigh.

I'll try again tomorrow in daylight, and with the standard halogen bulbs reinstalled, but if my L's still won't R in the D, I believe that leaves a modified relay as the last remaining suspect. Which means I have to figure out where the heck it is in the '06 RX330. (The pictures I've seen from a 400h don't match.)

At the same time, I did use Techstream to set the Auto light sensitivity from "NORMAL" to "Light2," which I believe will make the auto-headlights turn on at brighter threshold than usual. Options were "NORMAL," "Dark2," "Dark1," "Light1," and "Light2." This may be an acceptable compromise if I'm never able to get the DRL working again.