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Discussion Starter · #1 ·
I took my car in for service to the dealer this afternoon to drill and tap the license plate holder. In switching plates, one bolt had the head sheared off and was stuck. After an oil change, tire rotate/balance, I get the car back and notice the rear tailight indicator is illuminated. I checked all rear lights including running lights, and brake lights but none are out. I called dealer and was told that very, very few have a malfunctioning sensor and that I should double check.

Any suggestions? Closest dealer is 110 miles away....hoping to fix on my own or maybe at Toyota dealer.

Thanks!
 

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Double check. If you got a bulb out, which happens, you would not want to drive that far for such a simple thing.
Also, keep in mind bulbs do, sometimes, have intermittent problems. I had that happen to me. It took me a few tries to pinpoint which bulb was causing problems.

If you changed any of the bulbs in the past, make sure that they sit tight in the socket. That's what ended up being my problem - the bulbs were not plugged in all the way.
 

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nabisco212000 said:
ive gotten the same thing, i checked all the bulbs yet every once and a while that light comes on.

anyone guess why?
See my post above. Your bulb, probably, has intermittent problem.
 

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Discussion Starter · #5 ·
thanks for the tip. i have not changed any of the bulbs since i took ownership last december. it is my guess that something was either knocked loose or nicked during the drilling out and tapping of the bad bolt.

i spoke to the dealership again and was told that it may be sensing a bulb is about to go out and to monitor it.

appreciate the insight everyone!
 

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^^^^
It doesn't sence if the bulb is about to go out. The service dept is making it up. The system tests for resistnce of 2 coils inside of the bulbs. Should the resistance go up to a certain point (loose connection, blown coil), the Light Out indicator is triggered until you shut down your car. In other words, pay attention to when it lights up. If it lights up when you press the brake pedal, it is the brake coil of the bulb, or the 3rd brake light. If your parking lights are on and it lights up, then it is the parking light coil of the bulb.

What I had to do when I was hunting down my malfunction was to stop as soon as the indicator lights up, then do the bulbs check.

I don't see how a broken bolt could've affected wiring.
 

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Is there such a thing as two types of bulbs for the 7443? I bought a new 2-pack from a car store for $5 and replaced my right rear brake light after my dash sensor turned on, and now the light works but when I press the brake pedal the indicator appears - meaning the brake light does not work even though i replaced this with a new 7443.

Since you mention the brake coil, and sophiesleeps mentions the 4-prong bulb, is it possible that i purchased the "wrong" 7443, and there is a 7443 out there that once replaced will light up both the brake and lights, and cease the dash indicator from appearing?
 

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monkey_slayer said:
Is there such a thing as two types of bulbs for the 7443? I bought a new 2-pack from a car store for $5 and replaced my right rear brake light after my dash sensor turned on, and now the light works but when I press the brake pedal the indicator appears - meaning the brake light does not work even though i replaced this with a new 7443.

Since you mention the brake coil, and sophiesleeps mentions the 4-prong bulb, is it possible that i purchased the "wrong" 7443, and there is a 7443 out there that once replaced will light up both the brake and lights, and cease the dash indicator from appearing?
We both mean the same thing. There is only one type of 7443. Make sure the bulb is pligged in all the way. That was my problem with a replacement set I bought.
 

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Was it the rear license plate holder they worked on? If that's the case would the license plate lights trigger the indicator? Might want to check those.

Also sometimes some corrosion will build up at a bulb base and cause a poor connection. Cleaning the bases and sockets can fix that.

Also sometimes if a warning light has come on, and the problem fixed, the light won't go out until you reset the ECU.
 

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is300sam2002 said:
Was it the rear license plate holder they worked on? If that's the case would the license plate lights trigger the indicator? Might want to check those.

Also sometimes some corrosion will build up at a bulb base and cause a poor connection. Cleaning the bases and sockets can fix that.

Also sometimes if a warning light has come on, and the problem fixed, the light won't go out until you reset the ECU.
1) License plate lights do not trigger malfunction light.
2) ECU resetting is needed only for CEL (Check Engine Light). The bulb-out light will reset every time the engine is started.
 

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the taillight monitering system is much simpler than Alad_a says, the system does not in fact "check resistance " of the bulbs. It simply moniters current draw. If the system sees less/more curent draw than its "baseline" then it sets a malfunction light. note there are several baselines (one for tailights, one for brake lights, and another for tails and brakes. turn signals and lic. plate bulbs along with side markers are not monitered. for the origional question in this post. do you have a added spoiler with brake light? is it factory? factory spoiler cars will not have the rear window high mount stop if the spoiler has one. you did check the high mount stop right?? also i have found some aftermarket cheap bulbs seem to confuse the system. Your solution is simple, remove and check all your bulbs. if any filiments look nasty replace it. there isnt many, (four tails and the high mount)
 

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Lextech1 said:
the taillight monitering system is much simpler than Alad_a says, the system does not in fact "check resistance " of the bulbs. It simply moniters current draw. If the system sees less/more curent draw than its "baseline" then it sets a malfunction light...
On the resistance note, I=V/R. If R (Resistance) goes up, I (Current) goes down, V (Voltage) is constant.

In other words, one is inversly proportional to another.
 

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yes your right on the law of electricity. but in order to measure resistance of each bulb there would be lots of exra wiring and thus more cost. so lexus simply moniters the entire circuit without any extra wires via measuring the current draw on the main power supply wire.
 

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Lextech1 said:
yes your right on the law of electricity. but in order to measure resistance of each bulb there would be lots of exra wiring and thus more cost. so lexus simply moniters the entire circuit without any extra wires via measuring the current draw on the main power supply wire.
Let me rephrase.
Each bulb has certain resistance. Based on that resistance, there is a certain current draw. Should the resistance change, so will the current draw. Therefore, in this case, monitoring resistance or current is the same thing in the end.
 

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yeah, i know, and i agree with you. I thought you ment it was monitering each bulb seperatly. that would make the lamp failure computer stupidly complex. (although it would be nice for it to tell yah exactly what bulb was out )
 

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Discussion Starter · #16 ·
thanks for the info once again. i havent been able to check each bulb individually, but with the weekend approaching, i should be able to do so.

my IS is stock...no body mods whatsoever. only thing ive added is XM sat radio following the guide posted on IS300.NET, center arm rest and dash tray and finally tints.

i understand what you are saying in that the system monitors current draw collectively and individually.

when i do check the lights, i will be certain to by the 7443 bulb to avoid any future troubles!
 
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