Headlight problems

2001 tacoma

My low and high beams are not working.

4 fuses are good

relay is clicking, seems to be working and is allowing the daytime headlight option to function.

bulbs look good, not burned out, and the daylight setting is working.

Could it be the control switch?
Could there be a separate dimmer switch problem?

I am using the daylight setting on the control switch to drive at night, but this means no high beams and the lights seem dim. When I set the lights to "full on" position the lights go out. When I set to high beam, they go out.

 

I just ran the multi meter on the plug to one of the lights.

With the lights setting in the on position I get 14+ volts in all three contacts

with the lights on the daylight setting I get 14+ in the top position and 3volts in the other two positions.

I pulled one of the lights and it looks good. I checked continuity and I get good results on all the nodes.

Don't get it. Seems like I should have light.

 

bulbs both work in the daylight position.

anyone got a free wiring schematic for trouble shooting lighting system.
specifically the headlight and the dimmer relay?

 

I don't have access to the wiring schematic, and I know that the first gen drl system was pretty complex. However, from your description you are checking voltage at the headlights with reference to ground? In other words, one probe in the headlight plug, the other grounded? If that's true, then it sounds like you are losing the ground to the headlights.

I would try this: as you face the rear of the headlight plug, the common terminal that carries positive power into the headlight should be on the left. To confirm this, unplug both headlights and probe either headlight plug while disconnected. You should have positive power at the left side common terminal.

Still with me? Once you have confirmed that the positive is on the left (I don't want you to blow a fuse, and I'm only 95% certain), then you hook the headlights back up, and supply a ground to either the center or the right side terminal at the back of one headlight. If it lights up, you've confirmed you are missing the ground. On most Toyota trucks before the 2nd gens, the ground runs through the dimmer (hi/low) switch on the column. I would suspect that your dimmer switch has failed.

 

On one headlight socket I measured resistance and found way too much. I added a ground wire to the light socket ground (right hand wire if you are looking at the light) and attached it to the negative battery terminal. Lights are working in full low beam and high beam, but the slightly dimmer daylight setting is at full low beam.

Not sure where to go from here.

 

Just to clarify: when you say the ground wire is the right hand wire when looking at the light, am I looking at the back side of the light (under the hood) or am I looking at the glass side of the light (from the outside of the truck)

From the diagram, if you added a ground and now your lights work, then the DRL relay isn't supplying a ground to the lights in normal mode. Just as an additional test, does the "flash to pass" function work without your new jumper installed? The DRL 4 relay appears to be for "flash to pass", and the only other ground to the headlights is the main DRL relay on the left of the diagram.

 

This is looking at the glass from the front of the vehicle.

Before I added the ground, as part of my diagnostic, I took good relays , both dimmer and head from another vehicle (same part numbers), and put them in mine. I experienced the exact same problems. So I ruled out the relays, reinstalled mine and moved on.

Flash to pass works in all three settings on the light switch in the vehicle.

 

I believe the main DRL relay is bad.

The question is, is it worth replacing that relay ($), when you can just add a ground wire to each headlight, using wire that is the same size or larger as what is already there, and your lights will work. I don't see the downside to that. Sounds like the only side effect is the DRL function being brighter? Possibly shorter bulb life?

 

I know this is an old thread but has anyone had any problems before, i have a 2013 tacoma, both high beams work but the low beam on the passenger side doesnt work. Just replaced the bulbs with the same outcome. Kind of at a loss. Figured i would throw the question out just in case before i start tearing into things in case it happens to be some common problem.

 

2nd Gen truck is completely different from 1st gen, very straightforward. If memory serves me, ground wire is common to high and low beam functions at either headlight, and a single relay switches from high to low beam. So, your ground should be okay and the relays should be okay. I believe each high and low beam filament has its own fuse under the hood.

I would be checking fuses and checking that the plug at the headlight has a tight fit on the headlight bulb on the passenger side.

 

Ok cool. Thanks man. I will look into that.