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Weird backup/reverse light problem.

Old 11-30-2018, 04:15 AM
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Default Weird backup/reverse light problem.

I recently took on a stereo upgrade project in my 2003 350Z Touring (very light mileage, garage kept, in pristine shape (34k miles and only driven about 1k miles a year). I had a nice system before, but I have been unhappy with the outdated factory NAV and half the time it thinks I am driving around in the middle of nowhere as new roads are not visible within my last update several years ago. I have a Pioneer NEX Navigation HU in my other Nissan, and love it, so I opted to go with something similar here, and ended up buying a AVIC-8200NEX. I also wanted to add the audio controls from an 06 350Z, so I can have them at the wheel (along with the dimmable illyumination to match the car), plus keep the factory wheel appearance, which required me to install the 06 clock spring/spiral cable as well. I really don't need to go into any further detail on the sterrign wheel or the Pioneer HU, except for the fact that it has all the bells and whistles, including GPS, hands free phoning, steering wheel control inputs, and requires the vehicle speed line, parking brake monitor line, and reverse gear wire. I have the FSM from the 03 and 06, so it was not too much of an issue adding the steering wheel controls and I added the additional wires needed for thje illumination and audio controls from an 06 Z. There are threads here that are a huge help to accomplish this.

Anyways--here is my problem. At first, everything was working correctly and I could see my backup camera image, when dropping my MT into the reverse gear. Then it stopped working after a day or so, I think (I don't really know as the backup camera issue popped up around the same timeframe as the stereo/wheel install. I noticed another issue with the backup lights that I have never witnessed before with any vehicle I have owned and there are limited finidings of this instance on the web too. So, the reverse or backup lights stay on all the time, when the vehicles lights are on, whether in reverse or not. BUT, they get brighter when actually in reverse. I struggled to believe this until I actually measured the voltages at the reverse wire to confirm. So, in reverse, I get battery voltage (about 12v when engine is off, and about 14v when running, makes sense). When not in reverse, I am seeing 10-10.5V consistently on the same reverse wire. I believe that when out of gear, this reverse line should measure ground. This explains why I am seeign the reverse lights on all the time and why they are getting brighter when in the reverse gear.

After doing a bunch of research online, it seems to me that this may be related to a failed or stuck reverse light switch (the one that plugs into the manual tranny/gearbox, under the car). I find it odd that it happened in conjunction with my stereo install, but I am 100% sure that I didn't short or cross any wires related to the reverse gear wire, or any of the vehicles electronics. Everything in the car works, and I have not had to hunt any blown fuses, etc, after the install. So, I think the switch may have just died. I also don't know if this was like this before, or was intermittently problematic, because it was noticed after the stereo went in, and then the Pioneer HU was not detecting a difference between in reverse and out of reverse, enough to switch the backup cam on, so that is when I started digging in to discover this problem.

So, my stereo is in, everything looks great, but now my backup lights are on when I am driving--pretty annoying, and the backup camera is not working properly.

Is it the general consensus here that this is a failed reverse switch? Thanks for the help.

Last edited by onecoolee; 11-30-2018 at 04:41 AM.
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Old 11-30-2018, 05:43 AM
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It sounds like a switch issue or possible bad ground if you're 100% sure you did not accidentally connect the wrong reverse trigger wire for the back up camera.

But, it seems odd that the back up camera isn't working at all when you shift into reverse since the trigger wire should be getting the necessary 12v+ input. Or, if connected properly, the back up camera would be on 100% of the time if it's constantly getting the necessary 12v+ signal.

Is it possible that there is some type of connection from your new HU that is feeding a 12v+ signal to your reverse lights which is causing them to illuminate? That would explain them being on 100% of the time while your HU is on.
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Old 11-30-2018, 06:04 AM
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Originally Posted by Heel Til I Die View Post
It sounds like a switch issue or possible bad ground if you're 100% sure you did not accidentally connect the wrong reverse trigger wire for the back up camera.

But, it seems odd that the back up camera isn't working at all when you shift into reverse since the trigger wire should be getting the necessary 12v+ input. Or, if connected properly, the back up camera would be on 100% of the time if it's constantly getting the necessary 12v+ signal.

Is it possible that there is some type of connection from your new HU that is feeding a 12v+ signal to your reverse lights which is causing them to illuminate? That would explain them being on 100% of the time while your HU is on.
If I put the Pioneer HU in "battery" mode which looks for 12V on the reverse wire, the camera stays on all the time... I forgot to mention that, sorry and thanks for bringing that up. If I put the HU in "ground" mode, it never comes on at all, becase the voltage on that reverse wire never drops to less than 10V.

There is an illumination wire on the HU, but I believe its an input so the HU should not be feeding any of the lights in the car and the lights operate independently of anythign you do on the HU, even when its turned off--which is the way it should be.

Last edited by onecoolee; 11-30-2018 at 06:06 AM.
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Old 11-30-2018, 09:39 AM
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Originally Posted by onecoolee View Post
If I put the Pioneer HU in "battery" mode which looks for 12V on the reverse wire, the camera stays on all the time... I forgot to mention that, sorry and thanks for bringing that up. If I put the HU in "ground" mode, it never comes on at all, becase the voltage on that reverse wire never drops to less than 10V.

There is an illumination wire on the HU, but I believe its an input so the HU should not be feeding any of the lights in the car and the lights operate independently of anythign you do on the HU, even when its turned off--which is the way it should be.
Gotcha. That makes sense now about the back up camera and it being on constant since the reverse lights are constantly on. And you're correct - I'm fairly certain the illumination wire is to tell the HU to dim the lights when you turn on your headlights (if it's hooked up)

Found this post: https://my350z.com/forum/maintenance...-the-time.html

If it is the reverse light switch, I don't think they're too terribly expensive. Maybe try it and if it doesn't work, return it?
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Old 11-30-2018, 09:52 AM
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Originally Posted by Heel Til I Die View Post
Gotcha. That makes sense now about the back up camera and it being on constant since the reverse lights are constantly on. And you're correct - I'm fairly certain the illumination wire is to tell the HU to dim the lights when you turn on your headlights (if it's hooked up)

Found this post: https://my350z.com/forum/maintenance...-the-time.html

If it is the reverse light switch, I don't think they're too terribly expensive. Maybe try it and if it doesn't work, return it?
I already checked that thread out... it looked like the OP had an 03 and some things about the 06 were different, but he never reported back in after several years if he had his problem fixed... so I am not sure what the outcome was.

For the next step I am going to completely disconnect the reverse wire signal lead from my HU, just to make sure my HU is not pulling that up or down, when connected. Once I confirm that, and I don't anticipate finding that to be an issue, I will order the reverse switch and schedule the local shop to get it installed... I don't mind getting under the Z for oil changes and simple maintenance, but pulling it up on ramps and squeezing my fatass underneath the middle of the car to change out this switch probably won't be much fun on the cold garage floor.

Thanks for the the advice, and I will report back in with the final results when I do get it fixed and working properly.
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Old 12-07-2018, 03:40 AM
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All fixed... I had a revelation the other night, because I don't sleep well when things don't work. I remembered that in my original stereo installation, there was a Pioneer GEX TV tuner under the passengers seat--this module interfaced with the factory NAV, and required a reverse gear input signal. When I was removing all of the original equipment from 12 or so years ago, I pulled out 5 Pioneer IP-bus modules, including that TV tuner. I never paid any attention to the reverse gear wire that was hooked to this unit, as it was blue, so I assumed it was an amp turn on lead from the HU. Wrong assumption.

So, after tracing that wire, originally the reverse gear input wire was hooked to the NAV drive in the rear pillar (brown wire), which is an input. So, what was happening with my reverse lights was this--anytime the key was on, and the HU was on, the reverse lights were on, and at the amp trun on voltage (roughly 11V meaxsured from my Pioneer HU). When the reverse gear switch was activated, the liughts got brighter because the wire was seeing 12-14V from the battery. As soon as the wire was disconnected, everything worked properly and thankfully the reverse gear switch does not Ground the wire when not in reverse or that would have popped a fuse or link somewhere... so I guess when not in reverse its just an "open" and in reverse its battery voltage, and I believe thats what the shop manual shows.

Stupid mistake and 12+ years was too long to remember even hooking that wire up, but I am glad its fixed. New Pioneer NAV HU sounds great, and has Android Auto, handsfree BT, and all the bells and whistles. I was able to put my complete library of music on the SD flash drive installed in the HU...so this HU should provide a bit of future proofing too.
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