Honda Pilot - Honda Pilot Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
2012 Honda Pilot EXL- both rear brake lights wont come on when I apply the brake. Initially it was just one bulb that wouldn't come on and I replaced it but when I did it still wouldn't work. I swapped it with the another bulb from one of the other brake lights that worked and it worked. I swapped it back and when i did all of the brake lights stopped working. The top third brake light still works fine. I checked the fuse under the hood in the secondary fuse box no 11 marked "stop and Horn" it wasn't blown but I replaced it. Horn works and no change. I checked the mini fuses under the dash #15 and #19 and they were not blown. I checked the brake switch by unplugging it and when I did that the truck wouldn't switch out of park so I assume that's not it. There is supposed to be a 4th fuse box in the back but when I open the box marked "aux fuse" there is no fuse box in there. I see a bracket where a fuse box would be mounted and I even see the end of a harness but no fuse box. I am thinking this fuse box might be deleted if you didn't order the towing package? I saw another post about a black box that might get unplugged and it is located where the subwoofer panel is in the back passenger side by the tailgate. I haven't been able to find anything else online about this black box and getting to the subwoofer is very involved. Before I go down that road does anyone have any ideas? I think I'm going to replace #15 and #19 fuses under the dash just to play it safe. Any help appreciated.
 

·
Registered
Joined
·
2,256 Posts
The brake light circuits are amazingly simple. Fuse 11 (20A) in the under-hood aux fuse & relay box is the only wiring protection.

Circuit runs from that fuse through the underdash fuse & relay box (brown) (in at G16, out at F31), to the brakelight switch and then back into that same underdash fuse & relay panel at F30 (Light blue). There's a diode-isolated tap to the MICU part of that underdash fuse & relay panel specifically for the gear selector solenoid function. You tested that and verified that your circuit is all good to this point when you found the gear selector is locked with switch out.

The circuits to the light bulbs are all in parallel. Wiring for the left brake light bulb, the center high-mount stop lamp (CHMSL) bulbs, and the trigger lead to the optional factory trailer lighting control unit (missing per your description with no factory tow package) connect to the under-dash fuse & relay panel at E34 (light blue). The right-side bulb is connected at G8 on that same under-dash fuse & relay panel, but runs down the right side of the tub. The tail light assembly to connector to bulb socket wire color is green for both sides.

Conclusions: If the CHMSL is working, you should be looking at the tail light assemblies for breaks in the circuits to the bulbs. Might be bulbs, bulb sockets, or local wiring there. If the running lights work correctly, the ground side of these circuits is most likely intact. There are harnesses and connectors at the rear for the lighting groups, but all the circuits for one side (run, turn, brake, back-up) run in the same harness so unlikely that only one circuit in a harness would fail. Left-side wiring runs through the wheel arch where that towing module door sits, with the CHMSL wiring branching there (with ceiling light, rear wiper, tailgate lighting and switches plus camera wiring). Right side is a lot simpler, with only the right tail light wiring passing down that side.
 

·
Registered
Joined
·
2,116 Posts
The brake light circuits are amazingly simple. Fuse 11 (20A) in the under-hood aux fuse & relay box is the only wiring protection.

Circuit runs from that fuse through the underdash fuse & relay box (brown) (in at G16, out at F31), to the brakelight switch and then back into that same underdash fuse & relay panel at F30 (Light blue). There's a diode-isolated tap to the MICU part of that underdash fuse & relay panel specifically for the gear selector solenoid function. You tested that and verified that your circuit is all good to this point when you found the gear selector is locked with switch out.

The circuits to the light bulbs are all in parallel. Wiring for the left brake light bulb, the center high-mount stop lamp (CHMSL) bulbs, and the trigger lead to the optional factory trailer lighting control unit (missing per your description with no factory tow package) connect to the under-dash fuse & relay panel at E34 (light blue). The right-side bulb is connected at G8 on that same under-dash fuse & relay panel, but runs down the right side of the tub. The tail light assembly to connector to bulb socket wire color is green for both sides.

Conclusions: If the CHMSL is working, you should be looking at the tail light assemblies for breaks in the circuits to the bulbs. Might be bulbs, bulb sockets, or local wiring there. If the running lights work correctly, the ground side of these circuits is most likely intact. There are harnesses and connectors at the rear for the lighting groups, but all the circuits for one side (run, turn, brake, back-up) run in the same harness so unlikely that only one circuit in a harness would fail. Left-side wiring runs through the wheel arch where that towing module door sits, with the CHMSL wiring branching there (with ceiling light, rear wiper, tailgate lighting and switches plus camera wiring). Right side is a lot simpler, with only the right tail light wiring passing down that side.
That's amazingly simple? Like War and Peace is an amazingly simple read about Napoleon's enemies? I got lost around fuse 49, terminal D22 at the muffler bearing junction to the MICUlizer. Can't we just stick a voltmeter on the bulb socket and work back towards the battery? Although as the author of more than a few novels here myself, I guess I shouldn't talk.... so ....

 

·
Registered
Joined
·
2,256 Posts
Hmmm....

Maybe "relatively simple" would be better. In many Pilot circuits, current flows through a power distribution fuse, and isolation relay, another fuse, and an interlock relay, then has fuses in individual circuits on the way to a final element. In contrast, the brake lights have one main fuse for all the pieces and parts, and current flow is managed in parallel until it gets to the under-dash fuse and relay panel. It doesn't pass through any fuses or relays there, but it does split into left- and right-side circuits. I gave the terminal numbers and wire colors used, a loose description of the harness paths, and shared how much diagnostics he'd already done based on his statements about the CHMSL working and the gear selector lever interlock working correctly.

I also shared that all those symptoms point to bulbs, sockets and connections at the tail light housings themselves. I shared the wire colors in the harness and on the tail light assemblies to look at. I didn't include exact intermediate harness routing or interconnect details, because those would only be important if there was some significant body repair damage done recently, where a wire or harness connector was damaged or left disconnected. I did suggest that, since the harness and connectors are shared with circuits that still work, those should be discounted to the bottom of the 'possible causes' list.

A very first question when helping remotely diagnose based on symptoms is "what did you work on last?" In this case, it was stated that the OP had been swapping bulbs and connectors/connections at the tail light housings. These clues from the OP, on top of the current flow symptoms he described, steered me to the tail light sockets bulbs connectors wiring as the most likely suspects in the diagnostic process. They are also amazingly easy to inspect and test.

Lastly, diagnostic processes are not always written for the immediate case. There's the risk (and hope...) that a future user way stumble on the thread while trying to diagnose a similar but maybe not identical set of symptoms. Having the relatively full description of the system might offer enough to them to figure things out themselves.

So... "relatively simple"?

;)
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #5 ·
Thanks for the replies guys I really appreciate you taking your time to respond. Just for s*it* and giggles I replaced the brake switch because I had it in my head that was the issue but unfortunately no luck. What is frustrating is that the lights work when you open the tailgate, set the alarm or turn on the head lights so I cant believe its a socket issue. There was one light that wasn't working when this problem started. I replaced the bulb but it still didn't work so to test that new bulb I put it in a brake light sockets that was working to test and when I did it worked..great I said so I put it back in the socket that didn't work and then nothing worked..all the brake lights went out..fuses are good..brake switch is good...I just was back there checking the wiring and nothing looks bad but then again everything is covered in black tape from the factory.Is there some sort of box or junction by the subwoofer that might have come unplugged? Are these bulbs double filament and could they all be out (not likely). I'm going to check some wiring schematics I have from a shop manual download and see if anything pops out.take a test light and multimeter and start back probing I guess...maybe get another bulb just for the hell of it and see if it lights.again thanks and if you can think of anything else please let me know.
 

·
Registered
Nobili spiritus embiggens pequeño sparus tyre.
Joined
·
9,266 Posts
Although as the author of more than a few novels here myself, I guess I shouldn't talk.... so ....
You, too?

Au contraire, mon frère. We authors should fully indulge in our acquired highfalutin privilege of free speech, be it for speaking our mind or losing it. A mind is a terrible thing to lose.



OP, multimeter time.

Also, just a couple of thoughts: Do you have trailer light wires? Is your liftgate latch a little loose?

Even if you don't disassemble, do check that those big, flat-headed bronze-colored Phillips screws holding the tailgate latch in place are nice and tight. I had to retighten at least one of mine. They're well hidden behind the plastic trim, so it's not obvious how to get to them. You have to remove the plastic screws then plastic pushpin grommets holding the plastic trim in place, then bend (takes a bit of effort) the corners of that trim away and out (I used a big flathead screwdriver) so you can get your Phillips screwdriver in there to do the tightening.

(Sorry about the blurry pics.)

View attachment 144835

View attachment 144836

View attachment 144837

View attachment 144838

View attachment 144839

View attachment 144834
 

·
Registered
Joined
·
2,116 Posts
OP, multimeter time.

Also, just a couple of thoughts: Do you have trailer light wires? Is your liftgate latch a little loose?
Let's dial out the bulbs, put a multimeter on the socket contacts and see if you have power. If you do, buy new bulbs. If not, work your way back towards the battery. If the high mount stop light has power, the lower stops lights should as well .... at least the left one ... they're on the same buss.

The high mount stop light harness branches out from the left stop light harness somewhere in the left wheel well ... check that area for joints (connectors or splices), also flex the harness to see if you get any life at the meter in the left stop light socket. Concentrate on the harness past the split where the high mount and other tailgate power branches off. You're looking for a break between there and the left stop light socket. I don't think harnesses just go bad unless they're stressed or pinched, so let's hope it's just bulbs.

Also, make sure the socket contacts are clean and making good contact with the bulb. Make sure you do not touch the bulb with bare hands.


145464
 

·
Registered
Joined
·
2,116 Posts
Hmmm....

Maybe "relatively simple" would be better. In many Pilot circuits, current flows through a power distribution fuse, and isolation relay, another fuse, and an interlock relay, then has fuses in individual circuits on the way to a final element. In contrast, the brake lights have one main fuse for all the pieces and parts, and current flow is managed in parallel until it gets to the under-dash fuse and relay panel. It doesn't pass through any fuses or relays there, but it does split into left- and right-side circuits. I gave the terminal numbers and wire colors used, a loose description of the harness paths, and shared how much diagnostics he'd already done based on his statements about the CHMSL working and the gear selector lever interlock working correctly.

I also shared that all those symptoms point to bulbs, sockets and connections at the tail light housings themselves. I shared the wire colors in the harness and on the tail light assemblies to look at. I didn't include exact intermediate harness routing or interconnect details, because those would only be important if there was some significant body repair damage done recently, where a wire or harness connector was damaged or left disconnected. I did suggest that, since the harness and connectors are shared with circuits that still work, those should be discounted to the bottom of the 'possible causes' list.

A very first question when helping remotely diagnose based on symptoms is "what did you work on last?" In this case, it was stated that the OP had been swapping bulbs and connectors/connections at the tail light housings. These clues from the OP, on top of the current flow symptoms he described, steered me to the tail light sockets bulbs connectors wiring as the most likely suspects in the diagnostic process. They are also amazingly easy to inspect and test.

Lastly, diagnostic processes are not always written for the immediate case. There's the risk (and hope...) that a future user way stumble on the thread while trying to diagnose a similar but maybe not identical set of symptoms. Having the relatively full description of the system might offer enough to them to figure things out themselves.

So... "relatively simple"?

;)
I think I was misunderstood. I didn't mean the circuit wasn't "extremely simple" ... it is. Especially as you point out, relative to the entire system which is like an 80 mph 4,000 pound rolling mainframe. Although even that is relatively simple compared to what the Perseverence circuits must look like.

I give you great credit for so accurately explaining the circuit in words. I'm guessing you took the time to avoid any perceived harm to any IP rights attached to it. I found it "relatively simpler" to take the circuit diagram in the shop manual I paid >$300 for and post less than .01% of it under the fair use exemption of the copyright law under instructional use for no commercial gain and lack of competitive harm. It just seemed more helpful and easier to visualize how few parts need to be checked.

If Honda or the publisher want to sue me for helping their customers at no charge, I invite them to try. Entire manuals are online, even in this forum, although that isn't a defense, only a reality. My apologies in advance if I misread your reason for the long technical, although very well written, circuit description which was a tad difficult for me to follow without the diagram in front of me. Perhaps that's just a personal problem, so just ignore me.
 

·
Registered
Joined
·
695 Posts
Brake bulbs are dual filament, and those two filaments are on completely different circuits. Though they do share common ground.
Step1 : On the under-dash fuse box, those 3 huge connectors with grey covers are E,F and G. Those covers can slide off if you squeeze them a bit
First, check that both E34 and G8:
1. Show no continuity to ground when car is running and brake pedal not pressed. (no shorts)
2. Show power (12V) to ground when brake is pressed.

Step two (can actually make it step 1)
With two taillight retaining screws out and taillight pulled, squeeze and pull out the rubber grommet where harness goes into the body. Keep pulling until you get the 5P connector. It will be foam-wrapped. No need to disconnect, just use multimeter probes from vehicle side.
Positions are:
1 (lt blue) - brake
2 (blue on left, pink on right) - turn signals
3 (red) - taillight/marker
4 (orange) back-up
5 (black) ground

Check (from vehicle side) that you have 12V between 1 and 5 when brake pedal is pressed. If this checks out, problem is somewhere in the tail light. Those wires can get pretty brittle with time. As you were messing with those sockets - pulling in, out - something could have broken. Check continuity from 5P connector pin 1 to brake bulb socket. You other lights work, so ground (pin 5) ought to be good, but check it anyway.
 

Attachments

·
Registered
Joined
·
3 Posts
Discussion Starter · #11 ·
Thanks everyone for your replies. I happened to find a half empty box of new bulbs in my garage so I figured I'd give it a try because I literally couldn't think of anything else to do and low and behold it lit up! I ran to the store and bought another two pack and I got the left side to work also! Sylvannia 7443. So the best I can figure is I got a bad bulb that only lit up once and then died on the right side and then coincidentally the left bulb blew when I was working on it. Then to continue my bad luck the bulb I replaced it with that I had in my garage was bad as well...unreal. So after all this $8 worth of new bulbs solved the issue...crazy. Thanks again.
 

·
Registered
Joined
·
2,116 Posts
Thanks everyone for your replies. I happened to find a half empty box of new bulbs in my garage so I figured I'd give it a try because I literally couldn't think of anything else to do and low and behold it lit up! I ran to the store and bought another two pack and I got the left side to work also! Sylvannia 7443. So the best I can figure is I got a bad bulb that only lit up once and then died on the right side and then coincidentally the left bulb blew when I was working on it. Then to continue my bad luck the bulb I replaced it with that I had in my garage was bad as well...unreal. So after all this $8 worth of new bulbs solved the issue...crazy. Thanks again.
Great!! Thanks for letting us know. Psssst ....LED bulbs last longer.


145503
 

·
Registered
Nobili spiritus embiggens pequeño sparus tyre.
Joined
·
9,266 Posts
Coincidence? I think so!

OP, been there.

Sometimes it's just a bulb.



A rare retraction, like they say in fancy newspapers :|:

Said passenger side map light continued to go off intermittently, even after my "fix."

The cause? Sometimes it's just a bulb. :|

In this case, according to the owner's manual, a 12v 8w festoon type bulb. The Canadian Tire store I dropped by just before closing only had that size in a 12v 10w, but you know what? Not only does it work fine, but I noticed the very slight increase in brightness made it equal to the driver side map light, whereas it had been slightly dimmer before, which leads me to believe that perhaps, just perhaps, the previous owner had put in a 10w replacement on the driver side, which led to an "imbalance" in wattage in the circuit and that led to the original 8 watt bulb being fed a slight surge which caused it to fail earlier.

I can already hear opposing counsel interjecting,"Objection, your honor; calls for speculation."


BTW Jim, you're doing your meme wrong. You've covered your dancing dude's face with your text macro. Being as how you're still learning, we'll let it slide this one time with just a warning and a compensatory happy dancing banana, the forum's official mascot for "Yay, glad you got it fixed."

145525
 

·
Registered
Joined
·
2,116 Posts
Coincidence? I think so!

OP, been there.





BTW Jim, you're doing your meme wrong. You've covered your dancing dude's face with your text macro. Being as how you're still learning, we'll let it slide this one time with just a warning and a compensatory happy dancing banana, the forum's official mascot for "Yay, glad you got it fixed."

View attachment 145525
It's a thought bubble. The dancing banana has limited apeel.
 

·
Registered
Nobili spiritus embiggens pequeño sparus tyre.
Joined
·
9,266 Posts
1 - 16 of 16 Posts
Top