Piston Slap: A GPS-targeting Sleeper Agent?

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: Shutterstock user Kaspars Grinvalds]

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.