HOW TO: 2 Minute Fix for FAULTY Brake Light Failure Sensor Module.
12-31-13, 10:01 PM
#1
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HOW TO: 2 Minute Fix for FAULTY Brake Light Failure Sensor Module.
Didn't see this posted anywhere so I figured I would take it upon myself to do so. Like many people before me, I ran into an issue with the brake lights on my 99 RX300. When I pushed the brakes, no lights would come on at all.
*First thing to do is obviously check the fuse. It was fine.
*Second, check power at the brake sensor at the brake pedal. These DO go out, but often times are NOT the issue. The two wires connected to the sensor are Green/Black and Green/White. The Green/Black comes from the battery and should have 12v. When the brake pedal is depressed, power flows through the switch and out of the Green/White wire. There isn't much room down there to fiddle around with testing those wires, so here is an easier way to test that below:
-The BRAKE LIGHT FAILURE SENSOR MODULE is located on the cargo area underneath the fabric lining. Once removed, it is a tan colored box clipped to the back side of the sheet metal. From HERE, we can test if the BRAKE SENSOR at the pedal is bad. As I mentioned above, once the pedal is depressed, it sends 12v through the green/white wire. This wire leads back to the BRAKE LIGHT FAILURE SENSOR MODULE in the cargo area. So here, take your voltmeter and test the GREEN/WHITE wire on the module harness while the KEY IS ON and the BRAKE PEDAL IS DEPRESSED. If your BRAKE SENSOR is working, you will get 12v. If you get no power, your brake sensor is bad.
*NOW...if you DO get power at the GREEN/WHITE wire, but you DO NOT have brake lights still, you will now test PIN #1 on the same harness. This is the GREEN/YELLOW wire. CHANCES ARE, you WILL NOT get 12v at this wire. Again, test with the KEY ON and BRAKE PEDAL DEPRESSED. If you DO NOT get 12v at the GREEN/YELLOW wire, then your BRAKE LIGHT FAILURE SENSOR MODULE is bad. This seems to be the most common issue when the brake lights don't work all of a sudden.
*****A NEW MODULE WILL RUN YOU UPWARDS OF $300 FROM THE DEALER!!!!*****
*We don't want to pay this ridiculous amount of money for a small plastic box. And with a couple minutes, you can fix the sensor YOURSELF and be back to working in no time.
These sensors are just like the main relays on Honda's...one pin in general ends up getting a broken solder joint. This is caused by many heat cycles on/off. The solder heats up when power goes through (BRAKES APPLIED) and cools when there's no power (BRAKES RELEASED). With the Honda relays, it is usually the starter solder joint that ends up cracking. Anyway, back to our modules. With the constant heat cycles and the robotic welds on the board itself, the design is prone to failure from the factory...AS WE KNOW.
*Once your module is out, take the blue cover off of the back, you will see the circuit board. You will see the pins for the connector along the top. PIN #1 is the one that we are working with here. It is where the GREEN/YELLOW wire will be when the plug is connected. If you check it out, chances are you will see that the solder has cracked and broken away from the pin. You will see all of the other solder joints are solid but the solder on PIN #1 looks like THIS:
As you can see, there is a clear difference in the way the solder flows. The pictures don't do justice to what you see in person, but it is definitely noticeable in my pictures.
*You can two one of two things here. First would be to use solder braid and remove all of the old solder, then resolder the pin afterward. OR apply a tad bit more solder to the already existing solder. The existing solder has become a cold solder joint due to cracking, as you can see. Reheat the old solder and flow new solder onto the pin. After you are done, you will get something similar to THIS:
After you flow new solder, you can clean up the surrounding area with your solder braid and alcohol. Put the blue cover back on the module box and plug it in. Step on the brakes and ENJOY the fact that you didn't have to spend $300.
My car is a 99, it took 14 years for the solder joint to fail like it did. Resoldering this with a GOOD solder joint should last the rest of the life of the car. I've repaired multiple Honda main relays like this and even years later, there hasn't been an issue again. My brakes are working perfect in the RX now. Time will ultimately tell how long this fix lasts, but just remember that the natural design of the module is prone to failure to begin with...so even if you were to buy a brand new module, it will fail again at some point. Maybe not before your car dies, but you get the point.
Hope this can help someone out!
*First thing to do is obviously check the fuse. It was fine.
*Second, check power at the brake sensor at the brake pedal. These DO go out, but often times are NOT the issue. The two wires connected to the sensor are Green/Black and Green/White. The Green/Black comes from the battery and should have 12v. When the brake pedal is depressed, power flows through the switch and out of the Green/White wire. There isn't much room down there to fiddle around with testing those wires, so here is an easier way to test that below:
-The BRAKE LIGHT FAILURE SENSOR MODULE is located on the cargo area underneath the fabric lining. Once removed, it is a tan colored box clipped to the back side of the sheet metal. From HERE, we can test if the BRAKE SENSOR at the pedal is bad. As I mentioned above, once the pedal is depressed, it sends 12v through the green/white wire. This wire leads back to the BRAKE LIGHT FAILURE SENSOR MODULE in the cargo area. So here, take your voltmeter and test the GREEN/WHITE wire on the module harness while the KEY IS ON and the BRAKE PEDAL IS DEPRESSED. If your BRAKE SENSOR is working, you will get 12v. If you get no power, your brake sensor is bad.
*NOW...if you DO get power at the GREEN/WHITE wire, but you DO NOT have brake lights still, you will now test PIN #1 on the same harness. This is the GREEN/YELLOW wire. CHANCES ARE, you WILL NOT get 12v at this wire. Again, test with the KEY ON and BRAKE PEDAL DEPRESSED. If you DO NOT get 12v at the GREEN/YELLOW wire, then your BRAKE LIGHT FAILURE SENSOR MODULE is bad. This seems to be the most common issue when the brake lights don't work all of a sudden.
*****A NEW MODULE WILL RUN YOU UPWARDS OF $300 FROM THE DEALER!!!!*****
*We don't want to pay this ridiculous amount of money for a small plastic box. And with a couple minutes, you can fix the sensor YOURSELF and be back to working in no time.
These sensors are just like the main relays on Honda's...one pin in general ends up getting a broken solder joint. This is caused by many heat cycles on/off. The solder heats up when power goes through (BRAKES APPLIED) and cools when there's no power (BRAKES RELEASED). With the Honda relays, it is usually the starter solder joint that ends up cracking. Anyway, back to our modules. With the constant heat cycles and the robotic welds on the board itself, the design is prone to failure from the factory...AS WE KNOW.
*Once your module is out, take the blue cover off of the back, you will see the circuit board. You will see the pins for the connector along the top. PIN #1 is the one that we are working with here. It is where the GREEN/YELLOW wire will be when the plug is connected. If you check it out, chances are you will see that the solder has cracked and broken away from the pin. You will see all of the other solder joints are solid but the solder on PIN #1 looks like THIS:
As you can see, there is a clear difference in the way the solder flows. The pictures don't do justice to what you see in person, but it is definitely noticeable in my pictures.
*You can two one of two things here. First would be to use solder braid and remove all of the old solder, then resolder the pin afterward. OR apply a tad bit more solder to the already existing solder. The existing solder has become a cold solder joint due to cracking, as you can see. Reheat the old solder and flow new solder onto the pin. After you are done, you will get something similar to THIS:
After you flow new solder, you can clean up the surrounding area with your solder braid and alcohol. Put the blue cover back on the module box and plug it in. Step on the brakes and ENJOY the fact that you didn't have to spend $300.
My car is a 99, it took 14 years for the solder joint to fail like it did. Resoldering this with a GOOD solder joint should last the rest of the life of the car. I've repaired multiple Honda main relays like this and even years later, there hasn't been an issue again. My brakes are working perfect in the RX now. Time will ultimately tell how long this fix lasts, but just remember that the natural design of the module is prone to failure to begin with...so even if you were to buy a brand new module, it will fail again at some point. Maybe not before your car dies, but you get the point.
Hope this can help someone out!
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01-01-14, 09:25 AM
#6
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Thread Starter
Youre welcome guys.
As far as the locstion of the module...it is in the drivers side rear quarter. Pull out all the plastic trays and the fabric lining on the side near the strut tower. Also the upper plastic panel around the rear window needs to be pulled away as well. Just need enough clearance to get a hand/arm behind there.
Youll see a thick wiring loom with two smaller bundles that branch off. One goes to the tail light amd one looks like it trails off near the back window. Its this harness that connects to the brake failure module. If you look closely you will see a squeeze-tab roughly 1 inch in length...should be tan colored. If you feel behind the sheet metal panel, youll actually feel the box. Its quite small.
I used a screwdriver to press in one side of the tab and push it back then just took the box out the rest of the way. From there you can pull the whole box out from behind all of the plastic panels and crap and do your power testing. From there, its just a matter of using a small flathead to remove the blue plastic cover and youll have access to the back of the circuit board where you will find Pin #1 EASILY by the way it looks
As far as the locstion of the module...it is in the drivers side rear quarter. Pull out all the plastic trays and the fabric lining on the side near the strut tower. Also the upper plastic panel around the rear window needs to be pulled away as well. Just need enough clearance to get a hand/arm behind there.
Youll see a thick wiring loom with two smaller bundles that branch off. One goes to the tail light amd one looks like it trails off near the back window. Its this harness that connects to the brake failure module. If you look closely you will see a squeeze-tab roughly 1 inch in length...should be tan colored. If you feel behind the sheet metal panel, youll actually feel the box. Its quite small.
I used a screwdriver to press in one side of the tab and push it back then just took the box out the rest of the way. From there you can pull the whole box out from behind all of the plastic panels and crap and do your power testing. From there, its just a matter of using a small flathead to remove the blue plastic cover and youll have access to the back of the circuit board where you will find Pin #1 EASILY by the way it looks
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Trick1978 (10-06-23)
01-11-14, 08:49 PM
#7
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Thread Starter
Just to update - brake lights have been working just fine ever since resoldering the joint for pin #1. I took the module back out to see if anything had changed and it still looks exactly the same as when I soldered it. 
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Trick1978 (10-06-23)
Trending Topics
01-19-14, 10:25 PM
#9
Good to see other folks success!!
[[/SIZE]
Yes it is good to see other folks having success with these threads. I have a 2000 RX300
and just love it. It looks like I will die before it will. Unfortunately, that is not a joke. But hey,
we all have to die sometime. I got a lung disease: never smoked~~~~
Still all is good. My Lexus is going strong. Ok, the gas mileage is not so good....
Nick
Yes it is good to see other folks having success with these threads. I have a 2000 RX300
and just love it. It looks like I will die before it will. Unfortunately, that is not a joke. But hey,
we all have to die sometime. I got a lung disease: never smoked~~~~
Still all is good. My Lexus is going strong. Ok, the gas mileage is not so good....
Nick
The following users liked this post:
leirazepol (04-27-22)
01-21-14, 08:26 PM
#12
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Trick1978 (10-06-23)
03-19-14, 09:08 AM
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any photos on getting to the module, how difficult to remove the panel to get into the area. The trays you mention, are they on the panel itself. thanks. I didnt even know my lights were out, got a citation and an order to inspect, cant pass inspection until I fix. thanks a million.
As far as the locstion of the module...it is in the drivers side rear quarter. Pull out all the plastic trays and the fabric lining on the side near the strut tower. Also the upper plastic panel around the rear window needs to be pulled away as well. Just need enough clearance to get a hand/arm behind there.
Youll see a thick wiring loom with two smaller bundles that branch off. One goes to the tail light amd one looks like it trails off near the back window. Its this harness that connects to the brake failure module. If you look closely you will see a squeeze-tab roughly 1 inch in length...should be tan colored. If you feel behind the sheet metal panel, youll actually feel the box. Its quite small.
I used a screwdriver to press in one side of the tab and push it back then just took the box out the rest of the way. From there you can pull the whole box out from behind all of the plastic panels and crap and do your power testing. From there, its just a matter of using a small flathead to remove the blue plastic cover and youll have access to the back of the circuit board where you will find Pin #1 EASILY by the way it looks[/QUOTE]
As far as the locstion of the module...it is in the drivers side rear quarter. Pull out all the plastic trays and the fabric lining on the side near the strut tower. Also the upper plastic panel around the rear window needs to be pulled away as well. Just need enough clearance to get a hand/arm behind there.
Youll see a thick wiring loom with two smaller bundles that branch off. One goes to the tail light amd one looks like it trails off near the back window. Its this harness that connects to the brake failure module. If you look closely you will see a squeeze-tab roughly 1 inch in length...should be tan colored. If you feel behind the sheet metal panel, youll actually feel the box. Its quite small.
I used a screwdriver to press in one side of the tab and push it back then just took the box out the rest of the way. From there you can pull the whole box out from behind all of the plastic panels and crap and do your power testing. From there, its just a matter of using a small flathead to remove the blue plastic cover and youll have access to the back of the circuit board where you will find Pin #1 EASILY by the way it looks[/QUOTE]
08-30-14, 07:29 PM
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Oh man hope this is the problem with mine. I already changed the Brake light switch, the bulbs and fuses and nothing seems to work. The Brake lights won't come on at all. But they work when I switch all the lights on. I don't know what to do anymore. Gonna go check this method and hopefully thats it.