• Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.

Center (3rd) brake light doesn't turn on at all

29 July 2023
To register a rebuilt titled car in CA, we have to do the usual SMOG but also the Brake and Lamp check. As part of Brake and Lamp, all original brake lights that came with the car has to be functional. My center brake light doesn't come on at all. This is the horizonal bar of LEDs under the wing. Ebay has new ones at $500 from Japan. I also saw a listing for a used one at $200, all cracked up. I didn't want to spend $500 on this just yet but need something quick.

I did all the usual wiring checks per the service manual and nothing. So I removed the led bar and had a good look at it. Right where the wire harness goes into the LED section, I saw something unusual, looks like a dead spider. That shouldn't be there.

Since my led bar had many cracks already, I decided to cut a piece off to see the inside. The dead spider is actually a resistor that had dissolved. If you look closely, there is another one under it, also dissolved into its elements.


I cut them out but there is not enough left to read the color codes to see the resistance of these resistors. Two red bars are all I can make out.

So I soldered some leads on the posts of the cut resistors and use clips to test different resistors to see if the bar will light up (bar hooked up to a 12V battery).
I started high (1 MOhm) and worked my way down. More and more LEDs would light up as I decreased the resistance. I stopped at 100 Ohm (each, there are two of them) and was able to light up most of the LEDs in the bar. A few didn't light up at all and a few were brighter than the rest. I left the LED bar on for 30 mins and the resistors were warm (but not hot) to the touch. I didn't want to go lower, why ruin a good thing.
Soldered the resistors in. Clearance is not good so the solder job is not visually appealing.
Then glued the cut piece using clear silicon glue. The part goes under the wing and is not visible at all.
Hope this helps someone in a pinch.
BTW, I passed Brake and Lamp but failed SMOG. HC measured at 111 while max is 85 (@15 mph), HC measured at 74 while max is 50 (@25 mph). CO and NO were a tick below max and they passed.

Thinking of an attack plan: fuel injector cleaner, switch out the cats with another set of used units, etc. Maintenance is up to date: new spark plugs, coils, oil& filter, O2 sensors (all 4 - I have a 95).
What year is the car?
Before you go out and replace your cats. Was the catalyst monitor set before the test. If the catalyst monitor failed to set then yes, you may have dead cats. If the monitor set, I would not go out and replace them just yet.

Since your car is OBDII, do you have a scanner that is able to display the PIDs in real time? If so, the short and long term fuel trim values and the O2 sensor voltages may give you an idea as to what is going on. If you are running high negative trim values then the ECU is trying to correct fuel over delivery and the problem might be leaky fuel injectors or excessive fuel pressure.

The other thing that can cause an engine to run rich is a manifold air temperature sensor that has gone out of spec and is reading cold or a manifold temperature sensor that has become crudded up with PCV and EGR residue which can cause it to read low. The manifold air temperature does not have a huge effect on AFR; but, I have no sense as to how much being below 14.7 changes free HC in the exhaust. If you have that OBDII scanner you should be able to read the manifold air temperature with the engine off (but switched on) and if it matches the ambient air temperature then the sensor is likely in spec; but, it could still be crudded up.
Old Guy, always appreciate you chiming in. I got OBDII to "Ready" for everything except for the cats. I couldn't get the cats to be in Ready after about 50 miles of mixed driving. I was hoping eventually it will be Ready but not yet. When I bought the car, it had cats but they were hollow (basically straight piped). Bought a pair of cats from ebay but one was visibly clogged with something. Tried various ways to clean it but couldn't dislodge much of it. I have another pair of cats coming from a forum member. If that doesn't work, I will look into the others as you mentioned. Got a bottle of injector cleans in the fuel tank just in case that does anything.
If the O2 monitors achieved ready status; but, the cat monitor failed to achieve ready status then dead cats would be a definite possibility.

I don't use it; but, Techron seems to be a favorite for some NSX owners. However, you have to be using it regularly for an extended period for it to do anything. If you purchase Chevron / Texaco / Caltex premium (all owned by Chevron) you are getting Techron in your fuel already; however, Caltex does not appear listed as a Top Tier fuel vendor. I just purchase my fuel from a Top Tier registered vendor so that the car is on a steady diet of fuel system cleaner which is probably a 'Techron like' package.