Have you looked at a wiring diagram?

 

No i haven't. I am several steps below a shade tree mechanic. haha. I wouldn't know what i was looking at if it wasn't for people like you doing write ups and diys.

 

Basically you went from step one of knowing the issue to step three of testing the issue. Step two is troubleshooting the issue. The wiring diagram will show the connectors, fuses, relays, switches, and other components to test.

 

I'm just not sure where to look for a wiring diagram to see if there is a relay for the high beams or how to test the turn signal switch to make sure it's working properly. I was really really hoping there was a relay that i could switch with the low beam headlights or something.

 

See if this helps...

 

one more symbols key to wiring

 

Thank you so much. I will take a look and see if I can figure anything out.

 

It's a "simple" looking diagram for just the high beam circuit. I will try highlighting it soon.

 

Not sure if this helps at all.

 

I am confused on how the relay I highlighted works in yellow. Otherwise this is what I believe how the high beams work. I am also not sure if the light blue DRL wire is relevant.

 

This is what I would test for:

1. Test for power from the high beam connector
2. Test for power from the high beam fuses
3. Test for power from the relay highlighted in yellow
4. Test for power from connector 2G pin 1
5. Test for power from connector 2D pin 8 and/or 9, which ever one or both is connected.

Options to consider:

1. Swap low beam relay(s) with other identical relay's

My assumption is that connector 2D pin 8 is the high beam wire as DRLs are typically high beams. My assumption is also that the ground wire is connected as you said that you got the high beams working by directly connecting the battery to the fuse. The circuit is relatively simple like I said before, I just don't get how the H-LP (HI) Relay works. I also sorta doubt you would need to go pass the ECU but don't take my word for it. Good luck!

 

Ok, thanks guys. I'm going to do some more testing and try to find that hi beam relay that is in the wiring diagram. I was unable to find it today during my searching.

 

Guys, please check your years. All the wire diagrams posted so far are 2011+ with separate high and low beam bulbs. 08-10 uses a different architecture for switching the H4 bulb. There was some confusion about the 2011 diagrams above though, just know they use a mosfet (see below) to control the DRL on the high beams. The mosfet can act like a relay or do PWM (pulse width modulation) to run the bulb at 40% for DRL. The 08-10's do the exact same DRL strategy for the low beams.

Unfortunately this is not going to be an easy replace a relay kind of fix. If you have DRL's (and most 08-10's do), there are NO relays for low and high beam on the 08-10 highlander. That symbol is a mosfet (semiconductor...basically a big transistor/solid state relay) See attached wire diagram. Basically in blue is what you did when you connected 12V to the fuse, you bypassed the mosfet and backfed the other bulb through the parallel circuit.

If these have failed, you will be replacing the entire engine compartment junction block as the mosfets are not user serviceable parts (this is why I built a relay harness to protect the mosfets when I put in high power HIDs).

To get to the connectors your going to need to remove the fuse block from the car and partially demo it. I've never done it so can't give any advice there, sorry.
But:
-You know the bulbs work once your put 12V to the fuse, so everything downstream of the fuse is good.
-You know the ECU is good because the combination meter (edit: sorry old habit, that's the gauge cluster) is showing the high beam symbol.
-You need to check the connection between the ECU and the engine compartment junction block and make sure its getting the right signals from the ECU.
-----in the wiring block pic, I circled a wire and wrote a 1. That is the high beam control wire. That wire should be 12V to ground when the high beams are OFF and GND when the high beams are ON.
-----in the wiring block pic, I circled a wire and wrote a 2. That is the headlight (lowbeam) control wire. That wire should be 12V to ground when the low beams are OFF and GND when the low beams are ON.


If your inputs are good, and your output is good when bypassing and powering a fuse, that leaves you with only 1 option, the mosfet has failed and needs replacement.

 

Wow, thanks everyone and sweeneyp for the detailed replies. I'm going to have to look at this in the morning with a fresh head and do some testing. This is definitely maximizing out my troubleshooting skills. Haha. Thank you again for taking your time out of your day to help.

 

If you post where you are, maybe a member local to you could assist if needed?

 

If yo post where you are, maybe a member local to you could assist if needed?

I'm in Lakeland Florida.

 

It would be helpful if posters would put some demographics on the year, and trim level of their highlander, as well as overall area they live in...

 

Not sure about trim (or how that affects ) , but the op mentioned in the first post it is a 2010 highlander.

 

Are you using a meter to verify if there is power coming to both the fuse input & output, if not to the relay terminals. If not I strongly suggest you get a meter.

 

I have used a meter to verify that there is no power going to either fuse on the high beam fuses, either left or right beams, on both the input and output. I'm at a spot that I'm unsure how to proceed due to my own lack of knowledge. I'm not really wanting to take the fuse box apart to check the mophets just because I'm nervous that I couldn't get it back together. I did take the cover off the column of the steering wheel but I'm unsure how to test if the switch is working properly. I do know that when I activate the high beams the indicator on the dash lights up like they are on Also, the vehicle is a 2010 Highlander limited edition v6.

 

I would suggest making sure there is either power from the pink wire connector 2D pin 9 and the black wire connector 2G pin 1. Also make sure that when you are testing this that the high beam switch is ON. If you are testing it off, you ain't doing much.

 

I have the Exact same problem with my daughters High Beam...

 

Yes, I took it to a local mechanic and was told I need to take it to the dealership. Their scan tool couldn't see anything wrong. For now, we just do without high beams but I think about it all the time, especially when I'm driving it.

 

I replace this part. Now my high beams working

 

Is that the entire fuse box? Was it hard to replace? That is so awesome you got them working. We just came back from a trip during Christmas and I could have used my high beams so many times. I really do miss them. When I get more time I will definitely look that part up

 

How much did the part run you? If you don't mind me asking

 

Biker5000, Did replacing the engine junction box that Kene37 suggested? Did it fix the no high beam issue. I have a 2008 Highlander Sport.

 

I replaced the 82720-48050 assembly in the fusebox and it fixed both the high beam issue and horn issue. $200 online. Easy replacement as described above. Thanks for the help, guys.

 

If you have a 2010 Highlander and test at the fuse and there is no power, sweenyp is correct there is no relay to test or swap out. Test at the fuse block and if there is no power there most likely this part needs to be replaced. TP1986 pn 82720-48050

 

Thanks everyone. This really helped me fix the no high beam issue.

 

So, what if we have the opposite? Buddy of mine has a 2010 and his high beams are stuck on, have to unhook the battery or pull fuses to turn off. Could it be the same part?

 

have him do the posting. Its his vehicle and to answer question etc.

 

Oh, well if the circuit opens pulling fuses and there is not relay from above. Something is holding the circuit active. What is turning it on. Headlight switch when running or comes on itself etc. Details are key as are conditions. The stalk light control on the steering wheel can cause odd symptoms, maybe this once used.

 

Ok, man, I've just uncovered ground wires burnt...oh the fun of tracing down burt wires all the way through the firewall..I'll keep an update here, appreciate the advice!

 

Something shorted dumping current down those ground feeds you found. Good luck

If there are non factory add on items disconnect or isolate them first. Typically the cause of weird issues and electrical faults.

 

Well, isolated the burnt wires, taped them back up, and still no luck. Apparently when he pushed the rear window defrost, it caused all lights to go off and then only his high beams work. I'm no mechanic, but I work on all my own stuff, this one may be a challenge! He's brought it to two different shops and, after some diagnostic money, neither found these wires...sounds like some folks taking advantage of his situation! Well, just ordered a new stalk and might just order a complete wiring harness with fuse box and just start over. Thanks again, and I'll keep ya posted.