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I suspect that the BACKUP switch itself (or the connector at the backup switch) may be the real culprit.

With the incandescent bulbs installed, ignition on, and shifter in reverse, measure the voltage at the following points:
1. Downstream side of the IG1 fuse;
2. B+ supply side of the backup switch;
3. Switched side of the backup switch.

If the voltage is low at the IG1 switch, you have excessive resistance in the wiring somewhere between the fuse and the battery;

If the voltage is low at the B+ side of the switch, you have excessive resistance in the wiring between the B+ side of the switch and the IG1 fuse;

If the voltage is OK at the B+ side, but low at the switched side, the resistance is within the switch itself.

One other thought ... are you ABSOLUTELY sure you don't have some other electrical accessory connected to, and drawing current from, the backup light circuit? Like a "converter box" or other jury-rigged wiring for trailer lighting?
 

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Discussion Starter #22
I suspect that the BACKUP switch itself (or the connector at the backup switch) may be the real culprit.

With the incandescent bulbs installed, ignition on, and shifter in reverse, measure the voltage at the following points:
1. Downstream side of the IG1 fuse;
2. B+ supply side of the backup switch;
3. Switched side of the backup switch.

If the voltage is low at the IG1 switch, you have excessive resistance in the wiring somewhere between the fuse and the battery;

If the voltage is low at the B+ side of the switch, you have excessive resistance in the wiring between the B+ side of the switch and the IG1 fuse;

If the voltage is OK at the B+ side, but low at the switched side, the resistance is within the switch itself.

One other thought ... are you ABSOLUTELY sure you don't have some other electrical accessory connected to, and drawing current from, the backup light circuit? Like a "converter box" or other jury-rigged wiring for trailer lighting?
Ok good notes. One clarification...when you say "backup switch" you are referring to the rear backup sensor activation button and not my aftermarket backup lights that I installed? My aux backup lights are running to their own relay under the hood and powered in one of the available KEY ON open slots in the fuse panel. I can get the exact here shortly.

I'll triple check everything again, but I don't think I have anything else wired to that. My lighting and electrical mods at this time include the following PLEASE NOTE - ALL DISCONNECTED DURING THESE TESTS):

1- Interior LED trim and accent lights.
2- Some LED PUCK lights underneath side mirrors that are tapped into the ceiling lights.
3- Fog/driving lights.
4- Rear Aux LED backup lights.
5- Aftermarket Pioneer stereo with Backup camera. Camera was originally tapped into that YELLOW/RED line. I have removed it completely.
6- Interior LED Map light

I did install the factory OEM trailer hitch harness that didn't come standard when i purchased my FJ new back in '06. I bought the part from Toyota directly. I could disconnect that perhaps?
 

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Watching this thread. I have a similar problem and noticed by backup lights were flashing in time with the beeps of the backup sensor. Disconnected the backup sensor from the tap (installed by the dealer before I bought the vehicle) and things improved, but lights will often flicker or die completely.
I strongly suspect that the tap has damaged the wire, and I do quite like having the backup sensors, so now that I have some time on my hands I might just pull the interior trim out (tap is behind the driver side tail lights) and solder it all together & heatshrink. If that doesn't work I'll check the switch, because working reverse lights are generally good to have :)
 

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Ok good notes. One clarification...when you say "backup switch" you are referring to the rear backup sensor activation button and not my aftermarket backup lights that I installed? My aux backup lights are running to their own relay under the hood and powered in one of the available KEY ON open slots in the fuse panel. I can get the exact here shortly.

I'll triple check everything again, but I don't think I have anything else wired to that. My lighting and electrical mods at this time include the following PLEASE NOTE - ALL DISCONNECTED DURING THESE TESTS):

1- Interior LED trim and accent lights.
2- Some LED PUCK lights underneath side mirrors that are tapped into the ceiling lights.
3- Fog/driving lights.
4- Rear Aux LED backup lights.
5- Aftermarket Pioneer stereo with Backup camera. Camera was originally tapped into that YELLOW/RED line. I have removed it completely.
6- Interior LED Map light

I did install the factory OEM trailer hitch harness that didn't come standard when i purchased my FJ new back in '06. I bought the part from Toyota directly. I could disconnect that perhaps?
The "backup lamp switch" is located on the transmission, and senses when the transmission shift linkage is placed in the REVERSE position. It's item #42 in the illustration below. It has nothing to do with the backup sonar system except to provide a signal that the transmission is in reverse.

Because of its location, it is exposed to mud, road salt, dust, and possibly oil leakage from the engine.

None of the other electrical accessories you mentioned or OEM trailer lighting harness should affect the backup lights.

1125701
 

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Discussion Starter #25
The "backup lamp switch" is located on the transmission, and senses when the transmission shift linkage is placed in the REVERSE position. It's item #42 in the illustration below. It has nothing to do with the backup sonar system except to provide a signal that the transmission is in reverse.

Because of its location, it is exposed to mud, road salt, dust, and possibly oil leakage from the engine.

None of the other electrical accessories you mentioned or OEM trailer lighting harness should affect the backup lights.

View attachment 1125701
I think you are 100% right on the switch being the potential culprit. I'm just going to go ahead and order a new one since its only around $40. I'll solder the tapped wire as well and see what happens. Thank yo.
 

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I think you are 100% right on the switch being the potential culprit. I'm just going to go ahead and order a new one since its only around $40. I'll solder the tapped wire as well and see what happens. Thank yo.
But ... rather than just blindly replacing parts, why not measure the voltage drop across the switch contacts, or the resistance when the switch is closed?

This is where your mid-grade digital multimeter will instantly pay for itself ... if the voltage drop across the switch is more than 100 millivolts when the switch is closed (in-circuit test), or the resistance is more than 0.1 ohm (switch disconnected from harness), then the switch is bad.

If these measurements are good, then the switch is NOT your problem.
 

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Discussion Starter #27
But ... rather than just blindly replacing parts, why not measure the voltage drop across the switch contacts, or the resistance when the switch is closed?

This is where your mid-grade digital multimeter will instantly pay for itself ... if the voltage drop across the switch is more than 100 millivolts when the switch is closed (in-circuit test), or the resistance is more than 0.1 ohm (switch disconnected from harness), then the switch is bad.

If these measurements are good, then the switch is NOT your problem.
Can you recommend a good mid grade digital multimeter?
 

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No clue where you're located, and I usually find that the majority of Harbor Freight tools should be considered "one-use, disposible", but I did purchase several HF Cen-Tech multimeters years ago for my kids to learn with, and they were actually of decent quality.

However, I don't see those models currently offered, but they do have an "Ames DM600 Digital Multimeter" that is relatively inexpensive ($39) and might meet your needs. Bear in mind that a good-quality multimeter like a Fluke will cost you $200 - $500, but that's way overkill for your application.

DM600 Compact Digital Multimeter 64014 alternate photo #1

DM600 Compact Digital Multimeter 64014 alternate photo #2

DM600 Compact Digital Multimeter 64014 alternate photo #3

DM600 Compact Digital Multimeter 64014 alternate photo #4

DM600 Compact Digital Multimeter 64014 alternate photo #5

AMES
DM600 Compact Digital Multimeter
 

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Discussion Starter #29
No clue where you're located, and I usually find that the majority of Harbor Freight tools should be considered "one-use, disposible", but I did purchase several HF Cen-Tech multimeters years ago for my kids to learn with, and they were actually of decent quality.

However, I don't see those models currently offered, but they do have an "Ames DM600 Digital Multimeter" that is relatively inexpensive ($39) and might meet your needs. Bear in mind that a good-quality multimeter like a Fluke will cost you $200 - $500, but that's way overkill for your application.

DM600 Compact Digital Multimeter 64014 alternate photo #1

DM600 Compact Digital Multimeter 64014 alternate photo #2

DM600 Compact Digital Multimeter 64014 alternate photo #3

DM600 Compact Digital Multimeter 64014 alternate photo #4

DM600 Compact Digital Multimeter 64014 alternate photo #5

AMES
DM600 Compact Digital Multimeter
Thanks! Ironically, I was having some of this behavior back when I initially installed the LED bulbs back in 2018. I was just cleaning out some of my FJ stuff and came across a brand new Backup switch I purchased :) I never installed it because the problem went away and the lights worked fine. Then about a year ago, the lights started to intermittently work. 6 months they stopped all together and I relied on my AUX backup lights. With the Coronavirus I finally had some time to investigate. I'm going to check the switch tomorrow (if its nots raining) and proceed from there.
 

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Discussion Starter #30
Thanks! Ironically, I was having some of this behavior back when I initially installed the LED bulbs back in 2018. I was just cleaning out some of my FJ stuff and came across a brand new Backup switch I purchased :) I never installed it because the problem went away and the lights worked fine. Then about a year ago, the lights started to intermittently work. 6 months they stopped all together and I relied on my AUX backup lights. With the Coronavirus I finally had some time to investigate. I'm going to check the switch tomorrow (if its nots raining) and proceed from there.
Hi, so I went ahead and swapped out the backup switch and BOOM! its working! I really appreciate all your time and efforts to help me pinpoint this issue. I have definitely learned a few things from this experience and feel liked a saved myself a bit of money at the same time. I also thought it would be helpful to attach this document that I had stored about the entire backup system and how it is wired and laid out. It help me understand all of this a bit better.
 

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Hi, so I went ahead and swapped out the backup switch and BOOM! its working! I really appreciate all your time and efforts to help me pinpoint this issue. I have definitely learned a few things from this experience and feel liked a saved myself a bit of money at the same time. I also thought it would be helpful to attach this document that I had stored about the entire backup system and how it is wired and laid out. It help me understand all of this a bit better.
Glad to hear that you verified that the root cause was high resistance across the switch internal contacts.

I sent you a Private Message requesting the opportunity to perform a failure analysis on your switch; please don't throw it away!
 

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Hi, so I went ahead and swapped out the backup switch and BOOM! its working! I really appreciate all your time and efforts to help me pinpoint this issue. I have definitely learned a few things from this experience and feel liked a saved myself a bit of money at the same time. I also thought it would be helpful to attach this document that I had stored about the entire backup system and how it is wired and laid out. It help me understand all of this a bit better.
dantonb14, are you still out there??

Please check your messages ...
 
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