By on January 31, 2017

Lexus LS430 Aftermarket Navigation Screen, Image: kyoei-usa.com

TTAC Commentator Waftabletorque writes:

Dear Sajeev,

I’m having an issue diagnosing a navigation system problem on my 2002 LS430. I’ve gone a few years with the GPS link not working, which means it no longer receives a satellite signal and defaults to dead-reckoning mode (the GPS symbol disappears on the touchscreen). It’s a nuisance issue but it’s low on my priorities.

It also happens that I’ve been using a dashcam for the last four years. I never linked the two together until I had a couple of dashcams go bad in 2016, and spent the whole summer without one. Well, my GPS started working again, and I chalked it up to a warm summer fixing some sort of electrical wiring fault in the antenna.

Once I got my fourth dashcam in September, I noticed my GPS stopped working again. It was getting cold in the mornings and I thought my good luck spell had ended. Then, it occurred to me that maybe the GPS gets disabled when the 12V was in use. I’ve since found that it’s true for all three of my 12-volt ports (cigarette lighter, arm rest, rear seat cigarette lighter).

None of my other electrical loads (seat heaters, defrosters, seat massagers, headlights, fridge, etc) seem to trigger this issue, and I replaced the car battery in 2013.

So, what’s my next step? Is this a grounding issue? Voltage issue? A conspiracy of aftermarket electronics deliberately disabling automotive functionality?

Sajeev answers:

Since this Lexus non-guru/Alldata account holder cannot know for sure, buy a wiring diagram (there are plenty on eBay), ask on a forum, etc., to learn if the GPS’ power supply is tied into one (or all) of the 12V cigarette lighters.  I’d be pretty shocked (pun intended) if such a correlation existed.

Well, aside from sharing the same 12V power source feeding the fuse box(s)…but I digress.  

Seems like 12V power sources aren’t “always on” for owners needing their nicotine fix/cell phone charge/etc without the ignition key.  That’s in stark contrast to the battery-eating feature of a previous Piston Slap Prius, so consider hard wiring your camera or doing the “12V always on” modification mentioned in the first Club Lexus hyperlink.

Or, get an adapter/installation kit, a Carplay/Android Auto head unit and send the antiquated, unreliable GPS system on a permanent vacation to the recyclers.

Standard of living raised and problem solved!

[Image: kyoei-usa.com]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice. 

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20 Comments on “Piston Slap: A GPS-targeting Sleeper Agent?...”


  • avatar
    NormSV650

    It’s a Japanese car. Remember the performance gains in the 90’s on Japanese cars by just adding more grounding?

    Our old 2012 Forester had similar weak electronics the power windows would slow to a crawl as you added another at the same time. Plus my cigarette tire pump word eat fuses in it.

  • avatar
    TR4

    GPS antennas are almost always powered with a regulated 5V from the nav system and fed up the coax. So it is highly unlikely that loading the 12V outlet would have any effect. More likely the dash cam is generating interference that wipes out the GPS signal.
    If you have an actual cigarette lighter, try it. It will load the outlet but will not generate any interference as it is simply a resistance heater with no high frequency electronics.

    • 0 avatar
      True_Blue

      Great idea – different device, same outlet. As long as it’s something not generating a signal that could interfere with the GPS functioning.

      Since it’s rare to see an actual cigarette lighter, and a phone/tablet/etc will also generate HFS, I’d suggest one of those little Glade Airwick 12V car air fresheners. Plus, your car will smell like spring inside, as you test. Hard to top that.

  • avatar

    This sort of thing is why I buy my subscription to Piston Slap. Oh, wait, this is free. Even better!
    Seriously, this is an area where I could justify spending more on the unit than the car was worth.

  • avatar
    PrincipalDan

    But built in sat nav systems are generally useless after a few years anyway.

    • 0 avatar
      dukeisduke

      True, especially that vintage. The nav system has to be updated via a DVD, for which the Lexus dealers want $$$. Ripoff. When I was a frequenter of Torrent sites, I would see lots of Lexus nav DVD images posted there.

    • 0 avatar
      Scoutdude

      Sorry but that old line is just BS, sure new roads are being built here and there but old ones don’t generally disappear. So while it won’t get you to your friend’s house in the brand new neighborhood it will still get you 99% or more of the places where you want to go.

  • avatar
    Waftable Torque

    Thanks for the reply. I took TR4’s suggestion and tried running the dash cam unplugged and on battery power alone. Sure enough, GPS signal gone!

    Since this is my 4th dash cam (they all seem to spontaneously die regardless of their price point), the logical conclusion means they all interfere with the GPS signal.

    And I tried a couple of 12V accessories, and wasn’t able to trigger the GPS to turn off. So the 12V is not the culprit here.

    So…am I the only one with both a GPS and dash cam whom this happens to?

    • 0 avatar
      Corey Lewis

      Could you get one with some kind of casing, or perhaps -put- a thick case around it to prevent the signal interference?

      Have you tried moving the cam further away from the GPS unit while it’s on? Turn it on and lay it in the back seat, see if it still turns off the GPS then.

    • 0 avatar
      TR4

      Many car manufacturers will cheap out and install the GPS antenna under the dash cover where it can pick up interference from devices inside the vehicle.
      Much better is a roof mounted GPS antenna, if you can tolerate the appearance and installation effort/expense. It’s a bit hard for the average DIYer to install this but you might find a local car stereo installer to be of help. If you go this route, try a temporary setup first e.g. a magnetic mount antenna on the roof before committing and drilling holes etc.

      • 0 avatar
        APaGttH

        This. Relocate the antenna that is almost certainly located under the dash, or on a sensor embedded in the dash.

        The sensor and pigtail can likely be bought on its own, negating the very time consuming and likely expensive chore of digging the existing one out.

        Run the wire up an a-pillar and simply mount right on the edge of the glass at the top of the windshield. With a much clearer view of the sky, harder to get interference.

        Given you’ve already solved that the issue is interference from your dashcam – this seems like a good fix. You might even want to search the internet and see if anyone else has located the GPS receiver – my guess is the answer is yes.

  • avatar
    dukeisduke

    Waftabletorque, I’m leaning toward the interference thing, too. Are you on the ClubLexus forums? Maybe someone there has seen the same thing.

    • 0 avatar
      dukeisduke

      Nevermind, I see you figured it out. What kind of dashcams have you been buying? I have a sneaking suspicion that a lot of them don’t meet FCC standards for interference.

      • 0 avatar
        Waftable Torque

        My first dash cam was made by Blackbox. While it lasted the longest, it was only a 640×480 unit, and couldn’t read a licence plate unless you were right at their bumper. The availability of dash cams was tiny in 2012.

        My second dash cam was a unit from The Original Dash Cam. That one died within it’s warranty period, but was such a hassle to return that I decided not to ship it back.

        My third dash cam was a Chinese unit almost identical to my Blackbox, except it was 1080p. The unit lasted a month before it literally bursted from the summer heat. It was only $30 so I didn’t bother trying a warranty return.

        The unit I’m using now is a SecurityMan CARCAM-SDE. I bought two, and both were defective for different reasons. I’ll eventually do a warranty return for both once the winter driving season is done. One will randomly turn itself off, the other won’t charge on a USB power bank.

        None of these have Bluetooth or any other wireless capability. My GPS antenna is roof mounted, so it never occurred to me that there would be interference.

  • avatar
    yankinwaoz

    It doesn’t take much to screw up a GPS signal. They are very weak. The GPS signal your satnav receives is on the UHF range. This range is also used by WiFi, Blutooth, cordless phones, etc.

    Perhaps the dash cam has a wireless transmitter in it as a feature (usually WiFi or Bluetooth). Can you go in to settings and turn it off?

  • avatar
    SP

    Whenever I plug in my dash cam, my GPS reports that I am at Moscow airport! Dash cams are very popular in Russia. Coincidence?

  • avatar
    05lgt

    You could build a grounded faraday cage for the camera, but since the thing is most likely leaking along / using the power cord as an antenna … Why is the GPS in my phone so much more resistant to noise than car GPS? Filtering? It’s the same signal to both. I guess the new phone beats the heck out of the old signal processing. Android Auto mod. Then use the phone as the dash cam and the GPS.

  • avatar
    Waftable Torque

    Just for closure, I was able to resolve the issue so I could have BOTH the GPS and a dashcam. I relocated the dashcam 6 or so inches up, so that it’s located next to the rear-view mirror instead of the dashboard. There’s minimal sight line blockage, but I’m not crazy about the power cable just hanging straight down.

    Now to figure out what that antenna on the roof is for…


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