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Discussion Starter · #1 ·
I have a 2009. My tail lights and licence plate lights are out. Fuse is Blown. Replaced fuse. Blew that one. bulbs are good, can not find any shorts in the external wiring or in the trailer hitch.

Was directed to wiring harness behind rear seats to check for shorts. Need to remove rear seat, or portions of it. Have browsed a few threads and was told you can "strip" certain bolts if you don't do it correctly so I was wondering if someone could elaborate on that and tell me how to get to those wires, thanks!
 

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I have a 2009. My tail lights and licence plate lights are out. Fuse is Blown. Replaced fuse. Blew that one. bulbs are good, can not find any shorts in the external wiring or in the trailer hitch.

Was directed to wiring harness behind rear seats to check for shorts. Need to remove rear seat, or portions of it. Have browsed a few threads and was told you can "strip" certain bolts if you don't do it correctly so I was wondering if someone could elaborate on that and tell me how to get to those wires, thanks!
Suggestion:
Factory wiring is captured in looms tightly affixed to the channels inside and under trim like entry sills and C pillar trim. Even a careless mechanic or DIY'er would have to try HARD to pinch any factory loom when removing/reinstalling parts in the a$$ end interior. "Shorts" don't just happen on their own so unless someone did something crazy careless, its doubtful factory wiring is damaged by seat components.

The key word here is "factory". IF your RL has been altered along the way with aftermarket or home grown wiring, then anything is possible and all bets are off. Strongly recommend determining if your RL has factory or aftermarket wiring before jumping into behind the seat investigation.

Go here for wiring instructions, scroll down to trailer hitch and download factory instructions for your model year. Should help you determine what's in your RL:
https://www.handa-accessories.com/ridgelineext.html

If you determine wiring is factory, I'd suggest rear seat removal is a rabbit trail to no where.

Still, in order to determine if wiring has been pinched by rear seat removal/installation, you shouldn't need to remove the entire rear seat assembly. Recommend removing upper rear seat first - because it's relatively easy - and it should allow access to areas all around the lower seat mounts. With trim removed, you should be able to lift carpet enough to see if wires somehow got smashed or damaged around the mounts.

If its determined there are no smashed or pinched wires around the seat mounts, you might need to gain access to the entire bed wall area for a full evaluation. But that effort would be last on my troubleshooting list.

If you decide to go the full Monte and remove both upper & lower rear seats, review the FSM instructions below. And have a helper close by when its time to pull out the lower rear seat.

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Discussion Starter · #3 ·
I don't believe it was pinched, the only thing I did was install and LED light bar, and led turn signals and I believe water go into the trailer harness. I checked wiring in the rear of the vehicle and have swapped a new fuse in several times... I can not find the short and do not know how to isolate where it is, so I must search everything. I feel this is one of those phantom electrical issues that will never be resolved.
 

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I don't believe it was pinched, the only thing I did was install and LED light bar, and led turn signals and I believe water go into the trailer harness. I checked wiring in the rear of the vehicle and have swapped a new fuse in several times... I can not find the short and do not know how to isolate where it is, so I must search everything. I feel this is one of those phantom electrical issues that will never be resolved.
If you can find a GOOD auto electric shop, this is where they really earn their money, and are usually quite good at it..... I've been amazed at how quickly they can resolve issues like this. This might just be one of those issues that makes a couple hundred bucks & a subject matter expert turn several months of frustrating endeavor into an hour or two.

Good Luck either way.
 

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I don't believe it was pinched, the only thing I did was install and LED light bar, and led turn signals and I believe water go into the trailer harness. I checked wiring in the rear of the vehicle and have swapped a new fuse in several times... I can not find the short and do not know how to isolate where it is, so I must search everything. I feel this is one of those phantom electrical issues that will never be resolved.
AH. I see. Somehow I linked your original description to tow package wiring. My bad.

FYI: the entire wire harness could be fully submerged in water with no ill effect. IMO: behind the seat inspection will be a frustratingly unproductive effort because there are too many other potential problem areas to eliminate before checking that area out.

When you "checked wiring in the rear" what does that mean? VOM looking for dead shorts? Visual inspection only?

I haven't glanced at the owner or field service manuals but am curious which fuse pops under what conditions.

For example, what fuse location pops? Does it pop instantly when turning on running/head lights? Are front running lights affected too?

You mention adding an LED light bar - but there are no details on how/where it is connected - or its relationship to when the rear running light problem appeared.

I agree with Mr. Dnick, you may be best off finding a quality shop to troubleshoot the problem - but even then, the details above need to be provided to them - that is, unless the keys are dropped off with the expectation they simply start from scratch.

The point is, help here or in a shop requires details. Spill the details here if you want to avoid the time, risk and cost of finding competence out there.
 

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Discussion Starter · #6 ·
Ok the fuse is under the hood, 15A Fuse 4

Front lights, DRLs, headlights etc work.

Front and Rear turn signals work. reverse lights work. Third brake light works. No running lights in the rear or licence plate lights. I visually looked for short wires, bad grounds etc. The harness quickly disappears into an area that can't be seen.

It blows instantly when the lights are turned on. Also the GPS map screen does not auto-dim as it did before this happened. The LED light bar was plugged directly into the trailer hitch connection. For a while the lights all worked perfectly if I left the trailer harness unplugged, but now even that doesn't work. I have since removed the LED light bar, but still have the issue. I don't have an issue taking it to a shop, but I hate paying people to do something I could potentially do on my own.
 

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So am I reading right that your aftermarket LED bar is being plugged into your Trailer Hitch connector??

If so, the FIRST question to be asked is: (drum roll please)

Is this an aftermarket wire harness for your hitch???

If so, they are notorious for causing a multitude of mystery problems for RLs.....
If you have an aftermarket harness, the only sensible recommendation is to remove it from your truck & replace with an OEM harness. This is a well documented issue if you want to search elsewhere on the forum.

If this is NOT an aftermarket harness..... then (backing out the door) "Carry On".........

:wink:
 

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YEP. When I read "trailer hitch wiring" in the OP, my head went straight to the known issues of aftermarket products so well documented in this forum. Even "the big names" have lotsa trouble interfacing with the RL.

Go back to the first response in this thread. Pull down the factory trailer hitch installation document. Go back & double check hardware and the pigtail connectors in the rear to ensure they are OEM. There is other info in that document that will be helpful - if you are handy at troubleshooting.

Owner guide refers to 15A fuse 4 as: "Small lights". The circuit path is pretty limited with or without tow package wiring. The trouble you are describing is "running light" related, so it follows brake, turn signals, e-flasher, ETC would be unaffected because that is an entirely different circuit. Reason I asked about front running lights is I see no reference to a separate fuse protecting front/rear running lights. But that doesn't mean it doesn't exist. While looking to help, details like that matter.

Whats the deal with the LED bar being plugged into the trailer connector? Was it being used to enhance back up illumination? Was it running light powered? Reverse light activated? Does "plugged directly into trailer connector" mean exactly what it sounds like - plugged in like a trailer would be? Or was it connected to wires behind trailer connector?

Sorry to ask so many questions but many folk come here looking for help but it takes many many posts to get to the bottom of potential problems.
 

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Good Move.....

Be advised; IF you do have an aftermarket hitch wiring harness, be sure to point that out to them & mention the "mystery" effects of similar harnesses on RL electronics. They may very well be unaware of this kind of anomaly.

We've never been able to narrow the "aftermarket" harness issue down to any particular makes or isolate the root of the issue... so as Northern points out, it is a hit & miss kind of thing. But make no mistake; certain harnesses wreak havoc on some RLs, and the effect is yet to be understood from root cause standpoint.... only that it is far-reaching & somewhat inexplicable when it strikes..... and completely resolved when the offending harness has been removed. Certainly hard to diagnose, except in the crudest trial & error fashion.
 

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Discussion Starter · #12 ·
I don't mind your questions. Yes this LED light strip was plugged into a 7 pin trailer plug, which went directly into the hitch/harness. How can I determine whether its the trailer harness causing the issue ? I have tried unplugging it completely and the fuse still blows. I did take it to an auto-electric shop, but while waiting I saw several invoices on the table in front of me, and they were $300, $425, $700... Don't have that type of cash to throw down right now so I need to see if I can repair it first, myself.

YEP. When I read "trailer hitch wiring" in the OP, my head went straight to the known issues of aftermarket products so well documented in this forum. Even "the big names" have lotsa trouble interfacing with the RL.

Go back to the first response in this thread. Pull down the factory trailer hitch installation document. Go back & double check hardware and the pigtail connectors in the rear to ensure they are OEM. There is other info in that document that will be helpful - if you are handy at troubleshooting.

Owner guide refers to 15A fuse 4 as: "Small lights". The circuit path is pretty limited with or without tow package wiring. The trouble you are describing is "running light" related, so it follows brake, turn signals, e-flasher, ETC would be unaffected because that is an entirely different circuit. Reason I asked about front running lights is I see no reference to a separate fuse protecting front/rear running lights. But that doesn't mean it doesn't exist. While looking to help, details like that matter.

Whats the deal with the LED bar being plugged into the trailer connector? Was it being used to enhance back up illumination? Was it running light powered? Reverse light activated? Does "plugged directly into trailer connector" mean exactly what it sounds like - plugged in like a trailer would be? Or was it connected to wires behind trailer connector?

Sorry to ask so many questions but many folk come here looking for help but it takes many many posts to get to the bottom of potential problems.
 

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Discussion Starter · #13 ·
It's difficult to put into words the rage and frustration I feel on this problem. I have a 2007 mazda with almost 200k miles and it's got no issues at all. I've tried disconnecting the trailer harness plug entirely (right behind the plug) and that does not resolve the issue. I have replaced nearly all the lights with LED lights and I initially thought that was the issue, but they worked for several weeks before this happened.

Also the auto dim of the navigation doesn't work either, and I imagine that runs off the same fuse somehow.
 

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It's difficult to put into words the rage and frustration I feel on this problem. I have a 2007 mazda with almost 200k miles and it's got no issues at all. I've tried disconnecting the trailer harness plug entirely (right behind the plug) and that does not resolve the issue. I have replaced nearly all the lights with LED lights and I initially thought that was the issue, but they worked for several weeks before this happened.

Also the auto dim of the navigation doesn't work either, and I imagine that runs off the same fuse somehow.
Suggest starting by following the cable leading from hitch location to where it connects to the factory cable leading from front of the truck. Assuming the hitch connector is factory installed or installed after delivery to the dealer - AND - it is connected to factory cabling, there should be an intermediate connection located somewhere between rear frame rail and license plate area.

The hitch socket has a short pigtail that connects to factory wiring loom.

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Follow that pigtail and disconnect it. Insert new fuse and test.

If all good, you've isolated the trouble to the hitch socket.

If the trouble persists, you've got something else going on - most likely in the control module up under the drive side knee panel near steering column.

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Its starts to get a bit more complex from here. But you can determine a whole bunch by following the factory installation instructions mentioned earlier in this thread. Don't shoot in the dark, pull that document down and read thru it.

Disconnecting primary input to the control module, testing, and disconnecting in reverse of installation should help isolate the issue IF the problem is in the hitch power circuit - which is FAR more likely than a failure in wiring running front to rear.

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You *should* be able to isolate the problem.

Come back if you get stuck. And post pictures! They can help others see what you've got and lend a hand.

Best of luck.
 
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