I put LED brake lights in my 5th generation accord. As typical, the dash panel brake light came on. I put the original brake lights back in and the dash brake light still comes on now. I confirmed both lights work. The brake light does not come on until I depress the brake. The brake reservoir is at a good level. I measured the circuit resistance by cutting one of the wires that feed into the right light and I got a 2.3 ohm reading with the car turned off. Does the ECU monitor the third brake light or just the left and right brake lights? I tried hooking up 6 ohm load resistors in series and parallel to introduce resistances from 1.3 to 12 ohms with no luck having the dash brake light disappear. I am stuck on how to troubleshoot further. Any suggestions?

 

There are 2 brake lights on the cluster. One is the light that should turn on when you pull the emergency brake. The other brake light is below the door open/closed indicators on the gauge cluster that warn you a brake light is out.

Which brake light is illuminating?

The brake light failure sensor only detects the rear bulbs and not the 3rd high mount brake light.

 

It is the light below the door open/closed indicator that illuminates.

 

That brake warning light is for the rear brake bulbs. There is a black box on the rear driver's side brake light housing that sends a signal back to the cluster if a bulb is burnt out. I don't have the electronics in front of me to provide specific tests. Since you worked on installing LEDs in that area, check to see if you damaged or grounded any wires and check that the connectors are plugged in securely.

Did you have to modify any wiring when you installed the LEDs?

 

I did check on the appearance of the sockets and cleaned the terminals. The lights shine with equal looking brightness when the brake is depressed. I only have a LED hooked up to the third light now. There were no wiring modifications to the left and right brake lights.

 

It has been a while since I worked on this, but I found something interesting. When it gets really hot outside, the dash brake light is off. I feel that the hot weather is changing the resistance in the circuit to a value that the failure sensor does not activate. Does this sound correct?
Would anyone be able to measure their circuit resistance or current so that I could get a reference value? I cannot find anywhere the range of resistance where the failure sensor does not trip.

 

I am using all led bulbs now. I checked the resistances of the incandescent bulbs (~1.1 ohms) vs. the LED bulbs (~10Mohm) and deduced that a load resistor (~6 ohms) is not going to do anything to put the LED light in the resistance range of an incandescent light. The resistance of a load resistor is negligible to that of a LED bulb. Resistance would have to be subtracted from the LED bulb to match the incandescent, which is not possible.
Therefore I rewired the brake light failure sensor to have the relays always open (attached) to prevent the warning trigger. It works to keep the dash brake light warning off all the time.