99 Nissan Pathfinder - no brake lights when headlights are on

[rose3694]

I read someone else's similar issue to this, however, I believe we have already gone through all their steps and still are having an issue.

When our headlights are off, when we press the brakes both brake lights (upper skinnier filament glows) and the upper mount brake light strip illuminate.

When the headlights are on, the running/parking lights (same bulb as the brake bulbs, again only the upper skinnier filament) and the upper mount brake lights all illuminate. The moment we hit the brakes, both tail lights go out completely, the upper mount brake lights gets brighter like it should when braking.

Thus far we have replaced the Headlight switch, the brake light switch, all fuses related to lighting. Replaced all tail light bulbs and even the front running light bulbs because those have been blown for quite some time.

We have even pulled both rear tail light assemblies and used a multimeter to check for current through each of the wires for the brake/parking light bulb sockets. We have as well pulled both back side panels and checked what we believe to be the ground to the body to make sure they were tight.

After all of these steps, we are still having the issue. Is there some place we might have missed checking beyond tearing apart all the electrical in the truck to find the short?

Basically, the Lower fatter filament is not glowing at any point. Obviously not how the bulbs are suppose to be functioning.

[centralcoaster33]

There is a rubber grommet thing that pushes the button/switch on your brake pedal. Is that intact and making contact with your new button? It looks like the piece in this picture:



I think a short should have you popping fuses, but I'm not sure. I have read that the contacts can get worn down and the ground doesn't work as well.

From what I read, you don't have brake lights at night, but you do during the day... Is that correct?

Have you seen this similar thread? need-help-with-a-brake-light-problem-short-t318500.html

Welcome to NICO Club!

[rose3694]

That went a long time ago and the holes have been filled with bolts. The brake switch and cruise control switch are being pushed and depressed fine. Spent my whole afternoon yesterday under the dash installing a new brake light switch to make sure that wasn't the issue. LOL It would have been a nice quick job had it not been for it being a 1/4" above the steering column providing basically no room to move :P

And yes that is the post I read that described my exact situation. However, jiggling stuff has not gotten me anywhere and I don't see how spraying WD-40 would do me any good.

Thanks for the welcome

So tonight I brought the assemblies into the house and was testing with the multimeter with bulbs in their sockets. I had the multimeter just set to test for completed circuits. First I took the bulb out, put the black wire to the outside of the bulb and the red wire to one of the nodes on the bottom and got the same reading as if I was touching the leads together, same with the other. So I figured ok I should get the same reading with the bulb in the socket. Touch the black to ground in the harness plug and the other to either of the wires for the filaments for the brake light and could not get the same response, got an infinity reading. But touching the red to any of the other tail light bulbs connections in the harness got a complete circuit. So I don't know if I am expecting something I shouldn't or the brake light sockets on both sides are caput.

Thoughts? Am I going about testing this all wrong? LOL Is my explanation of what I was trying completely confusing?

I've already dropped over $100 in parts that we did not need to try and fix this, and can not afford to take this to someone now. Not the week of Christmas

[rose3694]

And if the sockets are caput, how the heck am I getting brake lights when the headlights are off and running lights when they are on LOL

[Hawairish]

Do you have a trailer wiring harness installed?

FWIW, and in general, it is possible to make a bulb behave in the manner you are seeing. I did something like that for turn-signal side markers on my pickup truck long ago. When the driving lights were off, the turn signals and side markers flashed in unison. Then the driving lights were on, the side markers and turn signals would alternate flashing. It was a deliberate short.

I mention this because your scenario is effectively the same. As you know, the brake bulb is essentially two bulbs. There's a short somewhere.

Have you tried connecting only one taillight at a time? The FSM also shows the wiring path...try tracing the wire bundle and check for an pinches. also disconnect the 3rd brake light to take it out of the equation. If you do have a trailer wiring harness, disconnect it.

[rose3694]

No trailer wiring harness in play here.

Unplugged the 3rd light and lost all lighting in the back all together. And tried each of the tail lights with them unplugged with no change.

Can anyone answer what the wire is that runs under the middle piece at the back door and goes down into a hole that I feel like it goes into the bumper? I pulled its grommet out and it is a small harness with nothing plugged up to it.

I watched videos on how to installed trailer harnesses and hooking up to this is never mentioned, and I just thought that it might be a built in trailer hook up. But I'm not sure.

Going to get a 12V automotive test light today and see if I can find some answers using that instead of the multimeter.

[Hawairish]

That harness with the grommet is for the swing-out style rear tire carrier. When shorted it it'll light up a tire carrier light on the gauge cluster, used to indicate the carrier isn't fully latched. Not a factor here, of course.

I missed the part about the fatter filament not glowing at all...that is what is supposed to glow during braking, so yes, that is an obvious problem. In essence, the only "correct" brake light that comes on at any given time is the 3rd brake light.

Disconnecting the 3rd brake light should not affect the other lights, however. As you can see in the FSM wiring diagram (http://www.nicoclub.com/manuals/Pathfin ... der/el.pdf, EL-51), each bulb (including the two filaments in the tail/brake bulb) has its own power feed and its own ground (excluding the tail/brake bulb, which share a ground). These power feeds occur before the bulbs, so one bulb/filament out shouldn't impact the other (except in the case of a short, of course).

When you say, "tried each unplugged", you mean you only had one light assembly attached at a time? Have you tried any tests with only the tail/brake light bulbs attached? Have you tried hooking up the bulb to a separate power source, completely disassociated from the truck? A 9V battery should be able to produce a small glow from each filament.

Keep in mind, too, that the brake signal also goes to the ABS and ACSD (cruise control) modules. Barring some failure there that is ultimately grounding the signal (the 3rd brake light bulbs draw little current vs. the brake bulbs, and power goes to the least resistance), those are also potential sources. Could check the cruise control to see that it is able to set a speed, and cancel with brake-press.

[rose3694]

Ok thanks, I couldn't find anything explaining what that was, and correct not a factor here, my spare is underneath.

Yes I tested the bulbs with a battery and I was able to get both filaments to glow so the brand new bulbs are in fact good bulbs LOL, I was also trying to see if I could get enough juice through the wires on the tail light assembly to light the bulb while in the socket from the battery, but apparently the wires create to much resistance to light it that way.

I was wondering if the cruise control could possibly be connected. I will try and test that out tonight on my drive home and see if it is still functioning. We don't live in an area where I get much need to run that, so it never gets used. But when looking at the wiring I thought I was understanding that it was connected to the brake light wiring as well and had a thought about my Mom's Ford Escape, her cruise control quit working and she lost backup lights because of that. Always thought it was odd, but wondered if this could be somehow related.

Ok so going to check that tonight, and also going to use the 12V test light and probe around sockets and see what that tells me.

[rose3694]

Well using the test light accomplished nothing besides learning if I touched the ground wire and the round outer metal part of the socket at the same time with the alligator clip it pops the fuse for tail lights and then I get brake lights again (again only the upper skinny filament), but no running lights what so ever. When that happens the beeping for having the headlights on stops too.

Unplugging the 3rd upper light with the headlights on makes the running tail lights go out and I still don't get brake lights either.

It got too late so I did not get to check the relay or fuses for the ABS. Cruise Control is operating as it should though.

Also drivers side rear, when you remove the side panel back there, down in the hole there I found 2 black boxes wired up to all that. Does not look factory at all since it was held in that well with very aged double sided stick foam tape. One says it is a rechargeable battery?? What would need that?

We got this truck from my in laws a few years ago, so I have no idea what they might have installed. I'm attaching a picture.

[Hawairish]

Yeah, that's odd. Old GPS tracker? Definitely not OE.

There is a taillight relay...perhaps try switching that with another relay?

[rose3694]

Here is my madness. I can not locate a Tail lamp Relay. I'm following the manual and stuff just not matching up. It also contradicts itself.

Page EL-320 Shows E115 being in Relay Box 1, Pg EL-321 says that is the Tail Lamp relay (Relay Box 2) huh?? Then again on pg EL-312 it shows a Relay being in that spot in Relay Box 1 calling it a Tail Lamp relay.

As you can see in my comparison picture, I have nothing in that top left corner. No wiring or plug or anything. Then I appear to be missing a Head Lamp relay. Not sure why that would be, or why my headlights are working properly if they are missing a relay.

So yeah here is a comparison of what I'm working with.
Heck, the cover for Relay Box 1 doesn't even match what is there, so I have no freaking clue.

Just a little history, the last time I had anything electrical worked on was over a year ago, our distributor was replaced. And then like 2 months ago we personally replaced our ignition. When it was noticed that we did not have tail lights with the head lights on and everyone's first thought was the headlight switch. When we pulled that out, there were metal filings all in the back side of the headlight switch because we went the hard route of taking the old ignition off not realizing the procedure of taking the steering wheel off. We basically hacked it off. We were very careful not to mess with any cords though. Everything appears fine under the steering column cover. SO anyways when we saw the metal filings we figured ok great that must be what happened, those probably shorted the switch out. However, yeah the new switch is doing the same thing.
Not sure if this might help with finding where else to look.

My husband sat and personally checked every fuse in the fusebox under the dash. I can not say the same has been done to all of them in the box under the hood, but the ones that are not clear are brand new fuses just for good measure because they were related to lighting or perhaps connected somehow.

[rose3694]

Even the fuse box diagrams do not match what we have. Is this normal? How can I even try and follow these diagrams if I hit a block of oh there is no fuse in that spot that the diagram says there is. Or there is no relay anywhere, where the diagrams say there is, nor a spot. This is absolutely maddening.

The truck was manufactured in 10/98 so I was like ok, let me go look at the manual for the 98, and yeah no, the 99 matches better, but still stuff is missing.

[rose3694]

PFFFT ok I see now, the 99 Nissan Pathfinder manual that is hosted here is for Serial# 350001, ours is #319490

Nissan does not make this easy.

[Hawairish]

I wouldn't worry about that missing ATP relay unless your truck is 4wd+AT. But it's unrelated to lighting, nonetheless.

So...there are actually two flavors of 1999 Pathfinders...1999 and 1999.5. It was mostly a cosmetic change, but there were several other subtle differences. In your case, consider your vehicle closer to the 1998 model than the 2000 model (especially when buying replacement parts).

That said, take a look at the 1998 FSM (http://www.nicoclub.com/FSM/Pathfinder/1998_Pathfinder) instead and you'll see it's consistent with your setup in that there wasn't a tail lamp relay (http://www.nicoclub.com/manuals/Pathfin ... der/el.pdf, EL-234). It looks like the running lights were split off to a separately-fused circuit at one point.

Let's take a step back for a moment. At any given time the brakes are applied, we know the following needs to be true for both RH and LH brake lights (measured at the bulb socket with bulb removed):

a) voltage between green w/yellow wire (+) and black wire (-) is 12V
b) voltage between green w/yellow wire to chassis ground is 12V
c) pink w/black to black wire is 0V
d) continuity exists between black wire and ground.

With that in mind, below are the troubleshooting steps I would do personally. You can leave the bulbs in for testing, but at some or multiple points (step #2 below would be best whether or not the test step passes), I would pull them to confirm those are true. Some of the steps you've probably already done, but entertain me since it's all done in sequence. Might be easiest to chart each each bulb's condition per step (RH tail, RH stop, LH tail, LH stop, 3rd lamp) to get a better idea of what is and isn't on.

1a. With all bulbs in place (bulb harnesses removed from tail light housing for observation ease), all fuses installed, ignition to off position, and headlight switch off, confirm all lights are off.
1b. Turn headlight switch to position 1 (if you've got an Auto light mode, ignore it for now); confirm tail lights and corner/running lights are on, stop lamps and headlights off.
1c. Turn headlight switch to position 2; confirm tail lights, corner/running lights, and headlights are on, stop lamps are off.

2. Press the brake pedal. Confirm stop lamps and 3rd brake light are on, tail lamps are off.

3a. Pull the "tail" fuse from the fuse box under the hood, truck off, headlight switch off, then repeat step #2.
3b. Turn the headlight switch to position 1, repeat step #2.
3c. Turn the headlight switch to position 2, repeat step #2.
3d. If 3b and 3c have different results, or if both 3b and 3c don't match step #2 results, disconnect the switch and repeat #2.

4a. Keep "tail" fuse removed, turn truck to ON (engine off, let all systems do their self-diagnostics and dash light checks first), headlight switch off, repeat step #2. If there's a failure here, could be ABS.
4b. Turn on the cruise control system (obviously won't be able to set a speed, but the system will be on). Repeat #2; if an issue exists, may be ACSD related. (For both of these steps, we can talk about pulling the ABS and ACSD fuses to further isolate those systems.)

5. Repeat 3a, 3b, 3c, and 3d with truck still ON (engine off).

6. Turn truck off, pull the "stop lamp" fuse under the dash, press brakes. Confirm all lamps off.

Based on your initial assessment, all except 1a-1c and 6 will/should fail. Let me know which step(s) deviate from expectation.

[rose3694]

Not going to be able to try this tonight. Will hop on this when I get home from work tomorrow. Thanks for all this. And yes you are very right, the 98 manual does look way more similar.

[Hawairish]

Any luck?

[rose3694]

Thank you for all your help. However, we gave up and took it to a mechanic. Had too many nights coming home in the dark and not having the tail lights on the interstate was getting dangerous.

It ended up being a loose ground in one fo the sockets. He soldered it in place and says we should be good now.

Now I just wish I had sprung for that little bit more money before hand and bought new tail light harnesses for $19 LOL

All fixed now. Thanks again for helping.