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Discussion Starter #1
Hello FJ and forum friends! So thankful for this site and community. I'm hoping someone out there can help me resolve a backup light issue I'm having. Hi, I have a 2007 FJ. I'm currently experience a low-voltage drop with my reverse lights. A few years ago I replaced the OEM backup bulbs with some Diode Dynamic bulbs. After some initial low output glitches the lights have worked perfectly. About 6 months ago the lights begin to intermittently stop working and then eventually stopped all together. I thought the bulbs might be the issue and had Diode Dynamics swap out the bulbs under warranty. That did not resolve the issue. Graciously, they then sent me their latest model that has built in resistors and unfortunately I'm still experiencing the same issue. A few years back I tapped the reverse light (yellow/red wire) underneath the drivers side door panel for a backup camera. I thought maybe that was the issue and removed the tap and camera. The lights still did not work. When I checked the cable at the TAP POINT the voltage reading was very low at around 8V. I replaced the rear backup light with the original OEM bulb, heard an audible BEEP, and then the voltage when back up to 12V. The LEDs and the OEM bulb lit up. I put the LED back in and everything seemed fine. However, eventually the voltage reading drops back down and the lights go dim or off. I have repeated this process a number of times. I do have a number of auxiliary lights (driving lights, backup lights, LED trim lights on the interior) wired up but nothing excessive. I also just had the electrical system checked out and alternator and battery are OK. I had them replace a bad Positive terminal cable and they said the vehicle's ground checked out OK. So, I'm at a bit of a loss here and hoping someone might have some insight to help me investigate where or how this might be happening. I'm going to replace the battery anyways, but I'm sure that is not it. Everything else with the electrical components are all operating normally. Thank you all in advance.
 

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How about the next time you read your 8 volts try something different. Run a wire to the negative side of the battery and check voltage


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Discussion Starter #3
How about the next time you read your 8 volts try something different. Run a wire to the negative side of the battery and check voltage


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Don't the OEM reverse light sockets ground back through the fuse panel? Could you explain that a bit more? Thanks!
 

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I question the integrity of the ground you used to read the 8 volts. Your putting in a new battery for some reason likely not associated with your initial problem. If your existing battery only had 8 volts it wouldn’t spin the starter motor. So do you have dirty terminals in your light socket maybe some corrosion going on that you don’t notice. Something in your voltage trouble shooting is flawed. If your trouble shooting is flawed you are going nowhere fast.


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Discussion Starter #5
What's even more weird...just testing everything again.
I question the integrity of the ground you used to read the 8 volts. Your putting in a new battery for some reason likely not associated with your initial problem. If your existing battery only had 8 volts it wouldn’t spin the starter motor. So do you have dirty terminals in your light socket maybe some corrosion going on that you don’t notice. Something in your voltage trouble shooting is flawed. If your trouble shooting is flawed you are going nowhere fast.


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That makes sense. I checked the sockets and at the place I tapped. I’ll try running a ground to battery to see. I’ll also spray some electronic cleaner on contacts to see if that helps. I also noticed A new behavior tonight.the backup sensors would only work when I removed the bulb. If the bulb was in the socket the rear sensors wouldn’t work even though they were switched on. This is definitely beyond my skill set. Thanks for your time. Really appreciate it.
 

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Discussion Starter #6
I question the integrity of the ground you used to read the 8 volts. Your putting in a new battery for some reason likely not associated with your initial problem. If your existing battery only had 8 volts it wouldn’t spin the starter motor. So do you have dirty terminals in your light socket maybe some corrosion going on that you don’t notice. Something in your voltage trouble shooting is flawed. If your trouble shooting is flawed you are going nowhere fast.


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I ran my meter to a different ground and were still getting readings of around 8V. Today, I noticed I had a full 12V reading when I had no bulbs in the reverse light sockets. With no bulbs in the rear backup sonar sensors would work as expected. When I put a bulb in the voltage would drop to zero or around 5V and the light would not work at all and the backup sonar sensors would not work. I'm so confused. I cleaned all the connection points, replaced fuse, etc... At this point I'll probably take it in, but was hoping to avoid that cost. Thanks.
 

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Are we using incandescent or led now? Poorly built LED can have some polarity problems. Poorly built does not necessarily mean inexpensive it can can also be a expensive poorly built LED. Quality control and quality forgiveness is typically better with incandescent, fewer parts to get in trouble with.


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Discussion Starter #8
Diode dynamics. I have tried 3 sets of leds and have gone back to original incandescent bulbs. still getting the same issue.
 

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OK, let's look at this step-by-step.

I assume that you have actually measured battery voltage, and confirmed that it is somewhere between 12.6V and 12.9V with the engine NOT running.

First, let's look UPSTREAM of the sockets, at the B+ supply to the backup light circuit. You stated that you had previously tapped into this wire to run a backup camera, had disconnected the camera, made a voltage measurement at the tap point, and saw only 8V.

The backup light electrical system is very simple. B+ for the backup lights is supplied directly from the battery through the ignition switch, the IG1 fuse, and switched via the BACKUP LIGHT SWITCH on MT vehicles, or via the PARK/NEUTRAL switch on AT vehicles. The switched power then goes directly to the backup bulb sockets.

IMPORTANT! Please clarify exactly which wire you tapped for your backup camera. The YELLOW wire with RED stripe (which you identified as the location of your tap) is the constantly-on B+ supply for the backup light circuit. If you actually tapped into this wire for your backup camera, it would have been on all the time.

The RED wire with YELLOW stripe is downstream of the backup light switch, and voltage is only present when the backup switch is closed (transmission in reverse).

(In Toyota schematics, the first color is the basic wire color, the second color is the ID stripe.)

So, if your tap point is truly on the YELLOW/RED wire, and you measured only 8V to a solid chassis ground, you either have high resistance in the wiring somewhere between your tap point and the battery, or the battery voltage is down around 8V.

If you actually did tap into the SWITCHED side of the backup light circuit (RED wire with YELLOW stripe) wire, and you are measuring 8V, then the suspect is high resistance in the backup switch contacts, or high resistance where the wiring harness connector plugs into the backup switch.

Go back and verify which wire you actually tapped into, and repeat the voltage measurement, making sure the ignition is on (but obviously with the engine not running), the shift lever is in reverse, and that you are picking up a solid ground point for your meter.

While monitoring the voltage at your tap point, move the shift lever rapidly between the P and R, or N and R, positions multiple times and see if the voltage stays at exactly 8V, or varies slightly with each shift. If it varies, the problem is most likely contaminated contacts within the reverse switch.

(Also, what type/make/model of meter are you using to make these voltage measurements?)
 

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Discussion Starter #10
OK, let's look at this step-by-step.

I assume that you have actually measured battery voltage, and confirmed that it is somewhere between 12.5V and 13.5V with the engine NOT running.

First, let's look UPSTREAM of the sockets, at the B+ supply to the backup light circuit. You stated that you had previously tapped into this wire to run a backup camera, had disconnected the camera, made a voltage measurement at the tap point, and saw only 8V.

The backup light electrical system is very simple. B+ for the backup lights is supplied directly from the battery through the ignition switch, the IG1 fuse, and switched via the BACKUP LIGHT SWITCH on MT vehicles, or via the PARK/NEUTRAL switch on AT vehicles. The switched power then goes directly to the backup bulb sockets.

IMPORTANT! Please clarify exactly which wire you tapped for your backup camera. The YELLOW wire with RED stripe (which you identified as the location of your tap) is the constantly-on B+ supply for the backup light circuit. If you actually tapped into this wire for your backup camera, it would have been on all the time.

The RED wire with YELLOW stripe is downstream of the backup light switch, and voltage is only present when the backup switch is closed (transmission in reverse).

(In Toyota schematics, the first color is the basic wire color, the second color is the ID stripe.)

So, if your tap point is truly on the YELLOW/RED wire, and you measured only 8V to a solid chassis ground, you either have high resistance in the wiring somewhere between your tap point and the battery, or the battery voltage is down around 8V.

If you actually did tap into the SWITCHED side of the backup light circuit (RED wire with YELLOW stripe) wire, and you are measuring 8V, then the suspect is high resistance in the backup switch contacts, or high resistance where the wiring harness connector plugs into the backup switch.

Go back and verify which wire you actually tapped into, and repeat the voltage measurement, making sure the ignition is on (but obviously with the engine not running), the shift lever is in reverse, and that you are picking up a solid ground point for your meter.

While monitoring the voltage at your tap point, move the shift lever rapidly between the P and R, or N and R, positions multiple times and see if the voltage stays at exactly 8V, or varies slightly with each shift. If it varies, the problem is most likely contaminated contacts within the reverse switch.

(Also, what type/make/model of meter are you using to make these voltage measurements?)
Hi FJtest, Thank you for taking the time to respond. I tested the line again today. I'm attaching a photo of the line that I have been using to power the backup camera. I original tapped this spot (under driver's side door panel) based on another forum posting. The camera would always turn on automatically when put in reverse when it was tapped in this spot, but you could be right that I tapped the wrong spot. Also, one correction. The line is actually a RED WIRE with a YELLOW STRIPE. (see photo).

I retested the line again and also ran a GROUND WIRE from the battery to double check that I was getting a good ground. Ground seems fine. What is happening now is this:

1- Battery is testing poor @ around 11V ( my mechanic confirmed this last week and will be replacing battery this week)

2- NO LIGHT BULBS in SOCKET - the line reads 10V and the BACKUP SENSOR SYSTEM works

3- ONE LIGHT BULB or TWO LIGHT BULBS in SOCKET - the line is DEAD and BACKUP SENSOR SYSTEM doesn't work.

4- PULLING BULBS AFTER TEST - There is an AUDIBLE BEEP (similar to when you stick the key in the ignition or engage the reverse gear) and everything works again.

5- Just a reminder that its 6speed manual. The LINE IS HOT when in REVERSE. The LINE is DEAD when its in NEUTRAL.

I'm using my grandfather's old meter which is a Micranta. I tested it with another meter and there readings are the same.

1125630
 

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OK, I think the photo of the wire and the damage caused by your "crimp-on, insulation displacement" tap may tell the whole story.

Unless they are very carefully installed, the crimp-on taps end up cutting multiple strands of conductor in the wire. Depending on how many strands were cut, this decreases the effective wire gauge, increases the resistance of the wire, and increases the voltage drop, so the voltage seen at the load is less than the supply voltage at the battery.

The fact that the voltage DROPS to 8 volts with the bulbs installed, and INCREASES to 11 volts with them removed, clearly indicates that you have a high resistance somewhere in the backup light circuit. The voltage drops as soon as you begin to draw any current through the circuit.

ACTIONS:
1. Get the battery replaced, verify the charging circuit is operating correctly, and that the battery voltage indicates that the battery is fully charged (around 13V).

2. Re-measure the voltage at your tap point WITH THE ORIGINAL INCANDESCENT LAMPS INSTALLED, ignition ON but engine not running, and shift lever in REVERSE.

3. Repeat measurement #2, but at the bulb socket with the bulb installed, back-probing from the wire-entry side of the socket.

Let us know what your voltage measurements are.

If you are going to try to perform any real electrical troubleshooting, you're going to have to get a modern, mid-grade digital mulitimeter that can accurately resolve tenths of a volt and tenths of an ohm.

Your grandfather's 40 year old "Micronta" (Radio Shack) analog meter probably isn't going to cut it. Comparing it against another uncalibrated meter of unknown accuracy doesn't achieve anything.

And never, NEVER us a crimp-on, insulation-displacement wire tap for ANYTHING.
 

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Discussion Starter #12
OK, I think the photo of the wire and the damage caused by your "crimp-on, insulation displacement" tap may tell the whole story.

Unless they are very carefully installed, the crimp-on taps end up cutting multiple strands of conductor in the wire. Depending on how many strands were cut, this decreases the effective wire gauge, increases the resistance of the wire, and increases the voltage drop, so the voltage seen at the load is less than the supply voltage at the battery.

The fact that the voltage DROPS to 8 volts with the bulbs installed, and INCREASES to 11 volts with them removed, clearly indicates that you have a high resistance somewhere in the backup light circuit. The voltage drops as soon as you begin to draw any current through the circuit.

ACTIONS:
1. Get the battery replaced, verify the charging circuit is operating correctly, and that the battery voltage indicates that the battery is fully charged (around 13V).

2. Re-measure the voltage at your tap point WITH THE ORIGINAL INCANDESCENT LAMPS INSTALLED, ignition ON but engine not running, and shift lever in REVERSE.

3. Repeat measurement #2, but at the bulb socket with the bulb installed, back-probing from the wire-entry side of the socket.

Let us know what your voltage measurements are.

If you are going to try to perform any real electrical troubleshooting, you're going to have to get a modern, mid-grade digital mulitimeter that can accurately resolve tenths of a volt and tenths of an ohm.

Your grandfather's 40 year old "Micronta" (Radio Shack) analog meter probably isn't going to cut it. Comparing it against another uncalibrated meter of unknown accuracy doesn't achieve anything.

And never, NEVER us a crimp-on, insulation-displacement wire tap for ANYTHING.
Thank you! That is a great lesson and I understand you completely. I'm definitely teaching myself and don't have much experience in this department, but I like learning and trying to work on my car myself. So thanks for you help. :) I get the new battery on Tuesday and will test again. Since I have compromised the integrity at my tap location would you advise me to just cut the wire completely and either solder the wire back together or using a wire connector?

Also, would those Posi-taps be a better solution or is that still something you would advise against.

Thank you in advance.
 

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Let's wait and see what your voltage readings are with the new battery before attempting any repair of the damaged wire.

Are you experienced with electrical soldering, have a good quality, appropriate wattage soldering iron, rosin-core solder, and heat-shrink tubing?

The best solution would be to cut the wire, perform a lap-splice, and insulate the splice with heat-shrink tubing, but if too many strands are NOT cut, you may be able to just tape the damaged area to insulate it.

One other thought ... do you have ANY other electrical loads that are being driven by the backup light circuit? Additional backup lights, etc.?
 

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Discussion Starter #14
Let's wait and see what your voltage readings are with the new battery before attempting any repair of the damaged wire.

Are you experienced with electrical soldering, have a good quality, appropriate wattage soldering iron, rosin-core solder, and heat-shrink tubing?

The best solution would be to cut the wire, perform a lap-splice, and insulate the splice with heat-shrink tubing, but if too many strands are NOT cut, you may be able to just tape the damaged area to insulate it.

One other thought ... do you have ANY other electrical loads that are being driven by the backup light circuit? Additional backup lights, etc.?
Ok sounds good. Not sure I will have a new meter by Tuesday, but I'll order one for sure. I have another one that I found in my family's stuff CB-instruments GMT-18A meter. Not sure that is any better.

I have a done a small amount of soldering over my lifetime. From RC cars as a kid, to stereo/speaker work, and now tinkering with aux lighting in the FJ. I have some 60/40 Rosin Core Solder wire, plenty of shrink tube.

I don't have any other loads currently hooked up to the backup light. I removed my backup camera from the reverse light at the present time, but hoping to somehow tie it back into the reverse light at some point. My AUX rear flood lights are manually controlled through an aftermarket switch that I installed.

As I previously mentioned it sounds like the rear backup sensor system is powered through the same cable because it won't work when I have lightbulbs in the socket.

Thanks.
 

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Ok sounds good. Not sure I will have a new meter by Tuesday, but I'll order one for sure. I have another one that I found in my family's stuff CB-instruments GMT-18A meter. Not sure that is any better.

I have a done a small amount of soldering over my lifetime. From RC cars as a kid, to stereo/speaker work, and now tinkering with aux lighting in the FJ. I have some 60/40 Rosin Core Solder wire, plenty of shrink tube.

I don't have any other loads currently hooked up to the backup light. I removed my backup camera from the reverse light at the present time, but hoping to somehow tie it back into the reverse light at some point. My AUX rear flood lights are manually controlled through an aftermarket switch that I installed.

As I previously mentioned it sounds like the rear backup sensor system is powered through the same cable because it won't work when I have lightbulbs in the socket.

Thanks.
The backup sonar system is powered through a separate circuit, but has a "sense" line connected to the backup light circuit to provide a signal to the backup sensor ECU to tell it when the transmission is in reverse and turn on the sonar system.

The "beep" you heard was from the backup sonar system as it was getting spurious low-voltage trigger signals from the backup light circuit. If the voltage in the backup light system is too low, it won't properly trigger the backup sonar system ECU to turn on.
 

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Discussion Starter #16
The backup sonar system is powered through a separate circuit, but has a "sense" line connected to the backup light circuit to provide a signal to the backup sensor ECU to tell it when the transmission is in reverse and turn on the sonar system.

The "beep" you heard was from the backup sonar system as it was getting spurious low-voltage trigger signals from the backup light circuit. If the voltage in the backup light system is too low, it won't properly trigger the backup sonar system ECU to turn on.
I thought it was a different circuit from what the manual says and the fuse box descriptions. Didn't know it had a "sense" line. Thanks for that info. I'll wait for the new battery and see how the voltage readings compare. Thanks for your time and help.
 

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Discussion Starter #17
So I installed a new battery today. The voltage is back up, but the same issues are prevalent with the backup light wire. It definitely could be my meter, but I'm getting similar readings.
1- At place of tap - jumps up to 11-12V, but then goes back down to 5-6V. Since it seemed to SPIKE a few times I think it could be the damage here. However, I could not duplicate the SPIKES.

2- The RIGHT REAR LIGHT SOCKET jumped up to 12V at one point, but pretty much reads around 5-6V. I tried a few different ground points to compare

3- The LEFT REAR LIGHT SOCKET pretty much is around 5-6V.

4- The line is completely dead with the OEM bulbs in the sockets.

My thought would be to try and repair the damage at the point that I tapped then line. Let me know what you think. Thank you!
 

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Discussion Starter #18
I thought it was a different circuit from what the manual says and the fuse box descriptions. Didn't know it had a "sense" line. Thanks for that info. I'll wait for the new battery and see how the voltage readings compare. Thanks for your time and help.
The backup sonar system is powered through a separate circuit, but has a "sense" line connected to the backup light circuit to provide a signal to the backup sensor ECU to tell it when the transmission is in reverse and turn on the sonar system.

The "beep" you heard was from the backup sonar system as it was getting spurious low-voltage trigger signals from the backup light circuit. If the voltage in the backup light system is too low, it won't properly trigger the backup sonar system ECU to turn on.
So I installed a new battery today. The voltage is back up, but the same issues are prevalent with the backup light wire. It definitely could be my meter, but I'm getting similar readings.
1- At place of tap - jumps up to 11-12V, but then goes back down to 5-6V. Since it seemed to SPIKE a few times I think it could be the damage here. However, I could not duplicate the SPIKES.

2- The RIGHT REAR LIGHT SOCKET jumped up to 12V at one point, but pretty much reads around 5-6V. I tried a few different ground points to compare

3- The LEFT REAR LIGHT SOCKET pretty much is around 5-6V.

4- The line is completely dead with the OEM bulbs in the sockets.

My thought would be to try and repair the damage at the point that I tapped then line. Let me know what you think. Thank you!a
 

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If there is sufficient wire free length, go ahead and perform a lap splice at the damaged area, overlapping the conductors by 3/8-1/2 inch and carefully soldering. Make sure to install the heat-shrink tubing before soldering, and slide it far enough away from the splice so it doesn't start to shrink during soldering.

I'm a little skeptical that your only problem is the damaged wire strands where you had your tap; there may be another high-resistance point in this circuit.

Perform the splice, and see if that completely resolves the voltage drop problem.

If not, the next steps are to check for any corrosion at the IG1 fuse, and check the backup switch for internal resistance.
 

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Discussion Starter #20
If there is sufficient wire free length, go ahead and perform a lap splice at the damaged area, overlapping the conductors by 3/8-1/2 inch and carefully soldering. Make sure to install the heat-shrink tubing before soldering, and slide it far enough away from the splice so it doesn't start to shrink during soldering.

I'm a little skeptical that your only problem is the damaged wire strands where you had your tap; there may be another high-resistance point in this circuit.

Perform the splice, and see if that completely resolves the voltage drop problem.

If not, the next steps are to check for any corrosion at the IG1 fuse, and check the backup switch for internal resistance.
Ok thanks. I'll do a lap splice and see how that goes, but I agree that I don't think its going to fix it. As far as checking for corrosion at the IG1 fuse. I have replace the actual fuse even though the other one look ok. If I was going to investigate for corrosion any further any tips on where to look?
 
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