[erik_26]

Hello my fellow forum members.

I have a 2015 SR5 4Runner. The front passenger low beam doesn't work.

I have checked the following:

New bulb = good

Lowbeam relay = good

both front lowbeam fuses = good

I have 12VDC at the fuse on the post

I have continuity to chasis ground on the bulb wire socket neautral wire.

I have zero continuity on to ground on the bulb wire socket positve wire.

I have zero VDC on the bulb wire socket to positive.


When I follow the wire harness from the fuse box towards the passenger light, if goes around the battery, behind the radiator tot he other side. It all looks to be intact and protected in the wiring hardness. I can't see it fully when it goes behind the raditor.


So I am not sure if it is a break in the wire somewhere or maybe corrosion under the fusebox, or something else?

Highbeam, blinker and foglight on passenger work. Only the lowbeam does not.

[fkheath]

Originally Posted by erik_26

Hello my fellow forum members.

I have a 2015 SR5 4Runner. The front passenger low beam doesn't work.

I have checked the following:

New bulb = good

Lowbeam relay = good

both front lowbeam fuses = good

I have 12VDC at the fuse on the post

I have continuity to chasis ground on the bulb wire socket neautral wire.

I have zero continuity on to ground on the bulb wire socket positve wire.

I have zero VDC on the bulb wire socket to positive.


When I follow the wire harness from the fuse box towards the passenger light, if goes around the battery, behind the radiator tot he other side. It all looks to be intact and protected in the wiring hardness. I can't see it fully when it goes behind the raditor.


So I am not sure if it is a break in the wire somewhere or maybe corrosion under the fusebox, or something else?

Highbeam, blinker and foglight on passenger work. Only the lowbeam does not.

Mice have a habit of chewing wires in out of the way places you can't get to.

Suggest doing a continuity check between each end you can get to. If there is no continuity, you will have to replace the wiring harness.

[Centrifugal]

Originally Posted by erik_26

Hello my fellow forum members.

I have a 2015 SR5 4Runner. The front passenger low beam doesn't work.

I have checked the following:

New bulb = good

Lowbeam relay = good

both front lowbeam fuses = good

I have 12VDC at the fuse on the post

I have continuity to chasis ground on the bulb wire socket neautral wire.

I have zero continuity on to ground on the bulb wire socket positve wire.

I have zero VDC on the bulb wire socket to positive.


When I follow the wire harness from the fuse box towards the passenger light, if goes around the battery, behind the radiator tot he other side. It all looks to be intact and protected in the wiring hardness. I can't see it fully when it goes behind the raditor.


So I am not sure if it is a break in the wire somewhere or maybe corrosion under the fusebox, or something else?

Highbeam, blinker and foglight on passenger work. Only the lowbeam does not.

-You bought this 4R used?
-Did the passenger low beam headlight ever work since you’ve had it?
-Did this suddenly happen?
-Are there any electrical mods to the headlight system?
-Are you sure the bulb is good? Did you test it in the driver side headlight?

Check the headlight socket pins for any corrosion or broken wire.
You can check for continuity from the fuse to the bulb. Do it for the driver side (left) as well as the passenger side (right). See diagram.

Good luck.

[thennen]

Originally Posted by erik_26

Hello my fellow forum members.

I have a 2015 SR5 4Runner. The front passenger low beam doesn't work.

I have checked the following:

New bulb = good

Lowbeam relay = good

both front lowbeam fuses = good

I have 12VDC at the fuse on the post

I have continuity to chasis ground on the bulb wire socket neautral wire.

I have zero continuity on to ground on the bulb wire socket positve wire.

I have zero VDC on the bulb wire socket to positive.


When I follow the wire harness from the fuse box towards the passenger light, if goes around the battery, behind the radiator tot he other side. It all looks to be intact and protected in the wiring hardness. I can't see it fully when it goes behind the raditor.


So I am not sure if it is a break in the wire somewhere or maybe corrosion under the fusebox, or something else?

Highbeam, blinker and foglight on passenger work. Only the lowbeam does not.

Is the wiring configured in such a way that you can connect a length of spare wire from the fuse to the bulb and bypass any potential breaks? Not as a repair, but to troubleshoot?

[erik_26]

Originally Posted by Centrifugal

-You bought this 4R used?
-Did the passenger low beam headlight ever work since you’ve had it?
-Did this suddenly happen?
-Are there any electrical mods to the headlight system?
-Are you sure the bulb is good? Did you test it in the driver side headlight?

Check the headlight socket pins for any corrosion or broken wire.
You can check for continuity from the fuse to the bulb. Do it for the driver side (left) as well as the passenger side (right). See diagram.

Good luck.

I have had it since 2016. The light used to work and one day stopped. No modification to anything, it is 100% stock. Highbeams on both sides work. Running lights on both sides work. The bulb is new, and tests good with a multi meter.

I will check the diagram, thank you.

[erik_26]

Originally Posted by thennen

Is the wiring configured in such a way that you can connect a length of spare wire from the fuse to the bulb and bypass any potential breaks? Not as a repair, but to troubleshoot?

I could use a jumper wire from the fuse to the bulb. I will try that.

The wiring harness looks good. I am afraid the issue within the fusebox.

I can't seem to find a good video on how to open the fusebox.

[Centrifugal]

Originally Posted by erik_26

I could use a jumper wire from the fuse to the bulb. I will try that.

The wiring harness looks good. I am afraid the issue within the fusebox.

I can't seem to find a good video on how to open the fusebox.

So did you get continuity in the wiring between pin 2 of the socket of fuse (10A H-LP RH-LO) and the low beam socket pin (Red-White wire)?

And does pin 1 of the socket of fuse (10A H-LP RH-LO) have +12V when you turn on the low beams? You can also make sure there is continuity between pin 2 of both fuses (10A H-LP RH-LO) and (10A H-LP LH-LO). If not then yeah you probably have an internal wiring issue inside of the fuse box. Make sure of this before you try opening the fuse box. I have seen a post somewhere of someone opening it to replace the 140A fuse and it’s pretty complicated.

[Humble Leader]

this is a longshot, but I'll leave these ideas here anyway just in case

- my wife had the same issue with her RX. daytime light though wouldn't work on drivers side. it was a 2010 and I guess what ended up happening is over the years the wiring harness or wiring itself became stiff (Idk what happened). but when I would move the harness around near the socket the light would go on. when I'd let it go - it would go off. I just separated the wiring from the main loom to give it more slack and not pull on the connector as hard and it fixed the problem

- when I replaced my 4runner low beams a few months ago I noticed the replacement bulb was really difficult to seat fully in the connector, despite being OEM replacement. I couldn't get it to fully click in even though it looked fine. had to warm up the connector a bit with a heat gun to get more play in that clip. then I was able to fully seat the bulb

unless you have rodent damage that you aren't noticing, given your troubleshooting steps I doubt the fuse box wiring just failed with no other cause

[Too Stroked]

How did you verify that the fuse was indeed good? If you just looked at it (visual check), you really didn't go far enough. You need to use a test light or continuity tester. I've had more fuses than I can count look good, but flunk that test.

[erik_26]

Originally Posted by Too Stroked

How did you verify that the fuse was indeed good? If you just looked at it (visual check), you really didn't go far enough. You need to use a test light or continuity tester. I've had more fuses than I can count look good, but flunk that test.

Used a multi meter to test DC voltage at the fuse posts, also checked continuity across the fuse and even swapped fuses with the working driver side lowbeam fuse.


I haven't gotten a chance to run a jumper wire for testing purposes yet. I will try that on Friday.