# 2019 Sentra SV security light ON



## Osaga (Dec 1, 2021)

Last week the security light came on (solid while driving) most of the time everything still works fine but once in the it won't start (key not detected) both fobs .. I can lock/unlock fine with remote... If I place the key right up to the button still nothing... And if I take the key out and lock/unlock the doors it won't lock/unlock all doors... Also the keyless entry does not work... I can try it 5 minutes later and all works,if not then using the key to unlock and seems to help it pick up the keys.. once it starts everything seems ok but I sometimes while driving it shows no key


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## Osaga (Dec 1, 2021)

I have only 26k miles on it and I'm told the warranty just expired Jan 2022


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## VStar650CL (Nov 12, 2020)

Have you changed the fob batteries? The RF systems for remote entry and keyless operations are completely separate circuits, RKE uses "garage door opener" FM frequencies while the keyless system uses much higher GHz frequencies more like your smartphone. Marginal batteries will cause all sorts of wacky behavior, even though the buttons may still work close to the car. Since the fob "squawks" constantly to the BCM while the car is running, it's also common for marginal fob batteries to "run down" and start the car okay but misbehave as the car is being driven.


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## Osaga (Dec 1, 2021)

VStar650CL said:


> Have you changed the fob batteries? The RF systems for remote entry and keyless operations are completely separate circuits, RKE uses "garage door opener" FM frequencies while the keyless system uses much higher GHz frequencies more like your smartphone. Marginal batteries will cause all sorts of wacky behavior, even though the buttons may still work close to the car. Since the fob "squawks" constantly to the BCM while the car is running, it's also common for marginal fob batteries to "run down" and start the car okay but misbehave as the car is being driven.


thanks for the reply.. we have replaced the batteries.. Im pretty sure its on the car side... why would both FOBs start to 'misbehave' at the same time? when the cars 'acts up' the remote start (separate remote) does not work... another interesting issue, my scan tool has some FOB functions and it shows remote ID when the FOB button is presses AND when the car is acting up, I can still LOCK/UNLOCK doors with remote BUT the scan tool doesnt pick it up..... but yes, quite wacky, I was gonna put it to ON position without pressing the brake and the car started?? 
the dealer wants $129 to diagnose... is there anything I can try??


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## VStar650CL (Nov 12, 2020)

The Sentras have a known problem with the brake pedal switches, there's a recall on the '16~'19's:


https://static.nhtsa.gov/odi/rcl/2021/RCRIT-21V135-8449.pdf



If your car started without pressing the brake then it's certain you have an issue with the switch. If the recall hasn't been done then it should be, if it was done then the switch is misadjusted. That can happen because they have us tape a rubber boot over the switch to keep dust out, but the nipple on the boot makes re-inserting the switch to the proper depth more difficult. You have to force it against the rubber to get the proper depth, and sometimes guys get lazy and don't push hard enough. That's something you can look at and fix yourself, the switch needs to be seated just deep enough that the switch plunger is completely depressed but not so far that it stops the pedal from returning fully. You can eyeball it easily with a flashlight.. 

Vis the screwy fob behavior, when the brake switch sticks it will run the car battery down, and that can of course cause security problems as well as jumpstarts. You should also make sure your new fob batteries weren't shelf-discharged, lithium cells are not immune to that. Put a voltmeter on them, 3.00V is the lower limit. Lithiums have a very flat discharge curve, so they're fully charged at 3.05V, flat at 2.99V, and totally dead at 2.96V.


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## Osaga (Dec 1, 2021)

thanks.. the brake switch/boot/grommet was done few days ago and thats when I was told that my warranty just expired so its $129 to diagnose the security... batteries OK... Im 99% sure its on the car side.. remote start was added 2yrs ago and has a 1 mile range so FOBs are nowhere near... when it 'acts up' it doesnt start either way... I'll see if I can disable the Viper remote start to rule it out


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## Osaga (Dec 1, 2021)

what can I do to test/rule out the FOBs?


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## VStar650CL (Nov 12, 2020)

Lol, if you're running aftermarket RS fobs then you're dependent on an aftermarket security interface. Dollars to donuts says your issue is somewhere in there and not in the factory system.


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## Osaga (Dec 1, 2021)

VStar650CL said:


> Lol, if you're running aftermarket RS fobs then you're dependent on an aftermarket security interface. Dollars to donuts says your issue is somewhere in there and not in the factory system.


UPDATE: so I had the AFTERMARKET RS completely removed, had the security error cleared and today the light came back on (code B2198)


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## VStar650CL (Nov 12, 2020)

That sounds like a harness issue between the BCM and the NATS antenna (the loop antenna around the start button), probably caused by splicing into the antenna wires. Check the wires carefully at both the antenna and BCM ends, somebody may have used a T-tap or scotchlok on the wires and it's causing a high-resistance condition when the BCM tries to transmit at low power.


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## Osaga (Dec 1, 2021)

thanks... thats the next step, taking it in to have the NATS/BCM wiring checked... at least there's progress and getting down to the root of the problem.. I hope


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