Thanks PA, yr a genius. I think we're getting close to solving this. Here's the results:

Drivers side:
green-white running into failure sensor: 12/13V
[brake light works, so no problem there]

Passenger side:
g-w into failure sensor: 12/13V
g-w out into brake lamp: 0V

So there is power running into the failure sensor but not back out again. I switched the sensor itself out already but didn't fix the problem. What/how would be the smart next troubleshoot?

 

Where did you test the grn/wht wire out, at the brake failure sensor, or at the bulb socket? Did you do the testing with the brake failure sensor plugged in?

 

Also, can you tell me the wire colors going to the passenger and driver's side failure sensors?

 

On the passenger side, there are four wires running in: green-white, green-red, green-blue, and green.

I tested the green-white before by sticking a pin through the wire before it enters the failure sensor (12/13V reading). I did the same with green-white wire running out of the failure sensor into the brake lamp casing/unit itself (0V reading).

 

1. At the harness connector to the right (passenger side) brake light failure sensor, test separately for voltage (+) on both the Grn/Red and Grn/Blu wires. Both should have voltage coming through the failure sensor with the brake pedal depressed.

2. If there is no voltage on both the Grn/Red and Grn/Blu wires, then try the following:

Locate connector C715, disconnect the plugs. Insert on end of a spare piece of wire into terminal no. 6 (Blk wire) and plug the connectors back together. Touch/connect the other end of the spare piece of wire to bare metal on the car's chassis (body). With the brake pedal depressed, does the brake lights work?



Inside the failure sensor are several relay circuits, that require power (+) and ground (-) to energize coils to close the relay contacts. If the replacement failure sensor is good, the cause is probably wiring and/or terminal contacts.

 

Hi Redbull,

Thanks, that's helpful. I checked the Grn/Red and Grn/Blu by pricking them on the lines running from the harness connector to the failure sensor. Got 0V reading on both of them w/ brake pedal depressed.

I then followed yr advice. I opened the harness connector/c715 and inserted a spare wire into the 6 slot (inside the C715) and then closed it up, depressed brake pedal and touched wire to chassis. Nothing happened to brake light bulb. I did the same thing, except now jamming the spare wire into the 6 slot (black) that runs out of the C715, pressed brake pedal and touched to chassis. Also did not light up bulb.

I used just a extra piece of low grade wire (and not auto electric) so let me know if that would cause a problem possibly.

 

For back-probing, I'd suggest pushing a t-pin into the back of the electrical connector for the wire you want to test.

Can you tell me the wire colors going to the driver's side sensor? Also the wire colors going to the passenger, driver, and high mount brake light? I'm trying to figure out which wiring diagram to use.

Also, when you replaced the failure sensor, what was the brand and part number you used?

 

Still sounds like an issue with the brake light failure sensor.

As a last resort, there is a way to bypass the sensor; but, it requires cutting part of the wiring. The Grn/Wht power supply wire would need to be connected directly to the following wires:

Grn/Red - Right Inner Brake Light
Grn/Blu - High Mount Brake Light
Orange - Right Outer Brake Light

Something like this Ideal push-in four port connector could be used.

Ideal 34 Yellow In-Sure 4-Port Connector (10-Pack)-30-1334S - The Home Depot

Do at your risk; but, should work.

 

Hi PA, the part number (written on outside is) DX SD 14. This came from a Honda dealership. I just switched this replacement failure sensor over onto the driver's side and it does work there (ie brake light comes on when pedal is pressed)--so it seems like the issue is not the replacement sensor.

The wire colors are as follows. Coming out of the driver's side connector harness: (level 1) green-red, red-black, green-white, green (2) white-green, black, green-yellow. Coming out of the passenger's side: (level 1) green-red, red-black, green-white, green-blue (2) green, black, green-yellow.

 

Hi Redbull,

I just switched this replacement failure sensor over onto the driver's side and it does work there (ie brake light comes on when pedal is pressed)--so it seems like the issue is not the replacement sensor?

Is there anything else you could think of? Maybe I should try cleaning the connector that runs into the failure sensor? I'm not sure the best way to do that...the openings are so tiny and maybe there is corrosion inside the housing?

I've got power flowing into the sensor (along the G-W) but not out...so maybe that could a place to troubleshoot?