No taillights

I've been searching the forms for about a week trying to figure this thing out but haven't had any luck...

Things I have done,
check the fuse inside the driver compartment, both fuse and power -- good fuse no power.
switched the relay around under the hood and still nothing.
new bulbs and check the pins in the rear no power at the bulb and the connector for the taillight housing with nothing.

my fog and license plate lights dont work all other rear lights work.

Did i miss a fuse? or another hidden relay somewhere?
its an 05 prerunner with no trailer harness.

my next guess was going to be a headlight switch any opposition to that?

 

Brake light switch maybe

 

Here is the schematic. Check to see if there's power to the relay. Check to see if the light switch is really providing a ground for the relay coil.

https://www.customtacos.com/tech.ol...6toyewd/06toypdf/ewd/2006/tacoma/h/em01d9.pdf

 

Yikes, I just realized that the that the tail relay is on the back side of the under dash fuse box. That's way difficult to get to.

 

So, I guess next, check the 50A J/B fuse in the under hood fusebox. If that is blown, it will also kill some other stuff too.

 

yeah okay thanks! This is what I was looking for. I saw those relays in the back but didn’t know which relay was which. Thanks.

Also do you know which 50a fuse to check? I wasn’t aware there was one connect to that circuit.

 

I’m not the best at reading wiring diagrams.
But it looks like the ground for the Fog Light Switch and the Ground for the Tail Light Relay use the same grounding point. - (J4a/J5b) Connector

If I understand the diagram correctly.
The relay needs to have a Ground, to allow the relay switch to close, and send power to the 10a tail light fuse?

I’m going to need @Muddinfun to be sure I’m correct?

The reason I bring this up, is because you say the Fog Lights and the Tail Lights do not work.

 

Sometimes a switch will send power through the relay to ground and sometimes the relays is powered and the switch connects it to ground. Dunno which this is.

 

Hmm okay. It’s just weird to me that I can’t pick up any voltage at any point. I haven’t check to make sure I got power at the relay so I’ll check that but thanks for the diagram and suggestions I’ll check them and report them back

 

That's a very good point. Things are a little bit different than I previously posted, but your ground idea could still apply. The headlight switch supplies a ground for the headlight and taillight wires that go the body ECU. The body ECU is what actually supplies the ground for the taillight relay. The foglight switch does share the same ground connection. So, if you are correct, then that means the headlights would not work either. So, tyoung05, do the headlights work?

 

Did you check the 50a J/B fuse? Is there voltage at that fuse?

 

I believe the Power Windows are feed from that fuse.
If the Power Windows work, the fuse should be good.

As you stated, Is there power to the Fuse.

Thanks again for all your help Muddin.

 

So switch the relays with the power window one still works, checked the 50 fuse and it’s good and has power. Trying to make sense of the headlight switch but can’t really. What pins should I be probing ??

 

Also my fog lights now work but no tail lights still

 

Do your Headlights work?

 

Yes

 

So, at this point, all of the easy obvious solutions are out the window. From here, you need to determine if power is getting to the relay, if the connection from the relay downstream is good, if the body ECU is capable of activating the relay coil and if the headlight switch is providing a ground circuit to the body ECU. One way that might point you in the right direction would be to jumper the 2 big taillight relay terminals in the fuse box and see if the tail lights come on. If they do, then you know the problem is in the relay control side. If they don't come on, then you need to see if power is getting to the relay terminals.

Study the schematic that I posted a link to so you can better understand how the circuit works.

 

If there is power through the pins #1 and #2 of the relay.
Would checking the voltage at Connector IJ1 - Pin #8
Let us know anything of value.
I’m not the best at reading Wiring Diagrams, but looks this would tell use if the problem is

In the body ECU or it wiring to IJ1 or the Fuse box?

Typung05, do not try this test.
Like I’ve stated, I a total novice at wiring diagrams.
There for, I wouldn’t want you to risk damaging anything.
I believe Muddin has a LOT more experience than me here.

 

have you spliced into any wires? Reason why I asked is because I did the 4x4 light mod on my truck and had two wires touching behind my AC controls and it kept blowing my fuses for my tail lights.