Lights/Radio Electrical

[SteinRunner]

Hi All

To be frank I posted this in the problems/warranty thread and soon figured the 3rd gen specific forum is the appropriate place for it. Apologies for the duplicate

I've run into a very peculiar issue with my 99 4runner limited and I believe it's mostly revolved around the lights. Please see below for a little detail.

Tail and sidemarker lamps remain on regardless of switch to the left of steering wheel being off or clicked forward once (you would assume this would turn them on).

After pulling head and taillight relay it seems as though the switch itself is working appropriately (when you click the switch to the left of the steering wheel forward once once you can hear the relay, and if you click the switch forward again to headlight on you can hear the relay once more).

After getting a little curious, I started trying different headlamp scenarios. I noticed regardless of key being in the car or not if you click the headlight switch forward once (this would generally turn on the tail and side marker lamps) the accessories power on (antenna, radio etc..) as well as the lamps.

This got me thinking maybe it has something to do with the accessories themselves so I pulled the accessory fuse. With the fuse pulled as you would expect if you turn the key to accessory nothing comes on. However, (this is with the accessory fuse pulled) if you turn the headlamps the same one click as previously explained the radio, antenna etc.. still powers up.

What's even further strange is, as long as the accessories fuse is pulled the headlights operate normally (i.e. with the key in the accessory or on position I don't have the tail and side marker lamps remaining on as I normally would in the off position).

At this point I'm starting to think somehow the headlamp switch is linked into the accessories or overriding them, but I know (or I'm almost certain) this should not be the case.

Apologies for the diatribe, but I feel as though there has to either be something stupid I'm missing or I truly do have a wiring issue.

Any and all help is greatly appreciated,

Josh

 

[vwtech]

You need a wiring diagram to see what powers what specifically, and usually when things are on that are not supposed to be on, or when you turn something on, and something else works, it is usually a ground issue.

 

[TheDurk]

Do you have anything aftermarket, alarm, etc. that might be tied into the headlights? Half the really weird stuff is due to crapo aftermarket installations. Otherwise, I have assume physical damage to wiring somewhere.

What year and do you have DRLs? (Very important, the circuits are quite different) I'll post some diagrams once I know.

What happens with the TAIL fuse pulled?

 

[SteinRunner]

As far as I know nothing aftermarket. I purchased the car from my aunt (she bought it brand new Jan of 99) a month ago and I'm truly unsure if the issue was there at the time of purchase.

It is however interesting you mention wire damage, after speaking with her she mentioned at one point mice chewed through a wire to the starter (she didn't know which one). The car wouldn't start and she had someone out to her place to replace it.

It's a 99 limited, DRL's I do not. Based on my ignorance I thought maybe that were the issue, but upon looking for the plug near the fender wall by the battery I realized it wasn't there. After digging in more I realized it were only the tail and side marker lamps staying on.

Also interesting you mention the tail fuse. When you pull the tail fuse the tails no longer come on using the light switch, however with the key turned to accessory bingo and they come back on.

Again, I'm fairly ignorant to the electrical system of this vehicle, the rear defrost doesn't work either, but I was planning on tackling that after getting the light/radio issue figured out.

 

[TheDurk]

Here is the Taillight circuit. This from 2002 but it is identical to the circuit in my '99 paper EWD manual.

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/024tl.pdf

Thanks be that you don't have DRL. I hate that circuit.

Anyway, you have already narrowed it down to the circuit in green with the fuse test I asked for. If you want to keep going, leave that fuse out and pull the 1C plug out of the Body ECU and see which lights come on with the accessories. Check both front and back.

You can see where Plug 1C is on p. 24 here (again, 2002, but same as '99):

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/relayloc/relayloc.pdf

We'll keep narrowing it down until we find it.

 

[SteinRunner]

Here is the Taillight circuit. This from 2002 but it is identical to the circuit in my '99 paper EWD manual.

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/024tl.pdf

Thanks be that you don't have DRL. I hate that circuit.

Anyway, you have already narrowed it down to the circuit in green with the fuse test I asked for. If you want to keep going, leave that fuse out and pull the 1C plug out of the Body ECU and see which lights come on with the accessories. Check both front and back.

You can see where Plug 1C is on p. 24 here (again, 2002, but same as '99):

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/relayloc/relayloc.pdf

We'll keep narrowing it down until we find it.

Hey Durk

Really appreciate the help on this one. Apologies for the not getting back sooner, I was traveling for work. Just had a shot to look at this.

Pulled the taillight fuse (under the hood)
Pulled 1C from the back of the body ECU (fun to get to)

As expected using the light switch (nothing). Turn the key to accessory and both the tail and sider marker lights comes on as they did previously.

Any thoughts on where to go from here?

Again, really appreciate it. Owe you a beer if you're ever in Cincy.

Josh

 

[TheDurk]

Hey Durk

Really appreciate the help on this one. Apologies for the not getting back sooner, I was traveling for work. Just had a shot to look at this.

Pulled the taillight fuse (under the hood)
Pulled 1C from the back of the body ECU (fun to get to)

As expected using the light switch (nothing). Turn the key to accessory and both the tail and sider marker lights comes on as they did previously.

Any thoughts on where to go from here?

Again, really appreciate it. Owe you a beer if you're ever in Cincy.

Josh

Need to know about the front parking lights....I assume they came on with 1C connected....this was the point of the exercise....

 

[SteinRunner]

Need to know about the front parking lights....I assume they came on with 1C connected....this was the point of the exercise....

If by parking lights you mean what generally occurs when you would click the the headlight knob once forward then yes. I think (my ignorance again) I'm calling it the side marker and tail lamps. Unless I'm missing a piece. I just want to be sure I'm getting it right.

What was occurring with the lamps happened with 1C connected and disconnected.

 

[TheDurk]

If by parking lights you mean what generally occurs when you would click the the headlight knob once forward then yes. I think (my ignorance again) I'm calling it the side marker and tail lamps. Unless I'm missing a piece. I just want to be sure I'm getting it right.

What was occurring with the lamps happened with 1C connected and disconnected.

Aww, crap. I must have had dirty glasses when I wrote 1C. I needed you to pull 1E. I'm very sorry. I hope you didn't put it all back.

Anyway, to move this along--if with 1E removed, the tail lights still come on, then leave 1E out and remove 1B and see what happens. That should get us well on the way to isolate what branch problem is on or if inside Body ECU.

 

[SteinRunner]

Aww, crap. I must have had dirty glasses when I wrote 1C. I needed you to pull 1E. I'm very sorry. I hope you didn't put it all back.

Anyway, to move this along--if with 1E removed, the tail lights still come on, then leave 1E out and remove 1B and see what happens. That should get us well on the way to isolate what branch problem is on or if inside Body ECU.

Continued diagnosis:

I pulled 1E which resulted in the side lamps up front no longer staying on with the key on accessory mode. The tail lights however stayed on.

I then pulled 1B and the drivers side passenger lamp is now out in accessory mode, but the passenger side remains on.

Any thoughts on the next place to look or thoughts?

Again, really appreciate all your help,

Josh

 

[TheDurk]

Continued diagnosis:

I pulled 1E which resulted in the side lamps up front no longer staying on with the key on accessory mode. The tail lights however stayed on.

I then pulled 1B and the drivers side passenger lamp is now out in accessory mode, but the passenger side remains on.

Any thoughts on the next place to look or thoughts?

Again, really appreciate all your help,

Josh

Excellent. That's real progress. The good news is you have ruled out the Body ECU, which is a really expensive part to replace. The short is between the 1B Plug Pin 5 and the passenger tail light. There is nothing in the light assembly that powers on with accessory, so I figure the fault is along that green wire to the passenger tail light from the Body ECU.

There are two places to break it so we can narrow it down further. Plug 3F in the Center Junction Box in the dash by the steering column tube, or Plug IL1, in the right kick panel. You can see where 3F is on p. 26 in the link above. Plug IL1 in the right kick panel, and is a white 3-row plug with 17 pins (6 vacant, so 11 wires) and you should see the green wire on PIN 16. Its a harness-to-harness type plug.

You get to choose which one you want to do first. Depending on what happens, you may not have to do the other one. Leave 1B disconnected while you do this. We should have it narrowed down to a relatively short run of continuous wire, so keep your eye open for any physical damage or ham-handed PO amateur wiring.

Good luck, and good work!

 

[SteinRunner]

Excellent. That's real progress. The good news is you have ruled out the Body ECU, which is a really expensive part to replace. The short is between the 1B Plug Pin 5 and the passenger tail light. There is nothing in the light assembly that powers on with accessory, so I figure the fault is along that green wire to the passenger tail light from the Body ECU.

There are two places to break it so we can narrow it down further. Plug 3F in the Center Junction Box in the dash by the steering column tube, or Plug IL1, in the right kick panel. You can see where 3F is on p. 26 in the link above. Plug IL1 in the right kick panel, and is a white 3-row plug with 17 pins (6 vacant, so 11 wires) and you should see the green wire on PIN 16. Its a harness-to-harness type plug.

You get to choose which one you want to do first. Depending on what happens, you may not have to do the other one. Leave 1B disconnected while you do this. We should have it narrowed down to a relatively short run of continuous wire, so keep your eye open for any physical damage or ham-handed PO amateur wiring.

Good luck, and good work!

I pulled IL1, easier to get to in my book, please don't judge. When pulling this the tail no longer comes on. The connection looks pretty lubed up whether that's good or bad. I can post a picture tomorrow if it warrants a look. Almost looks like someone smeared dielectric grease on it.

Any thoughts on the next move?

 

[TheDurk]

I pulled IL1, easier to get to in my book, please don't judge. When pulling this the tail no longer comes on. The connection looks pretty lubed up whether that's good or bad. I can post a picture tomorrow if it warrants a look. Almost looks like someone smeared dielectric grease on it.

Any thoughts on the next move?

Hmmm. Dielectric grease would not be an issue. But you never know if some nimrod used petroleum jelly instead. Dielectric grease does not conduct, petroleum jelly does and would really screw things up..

Do you have a meter or test light? I'd like you to test that PIN 16 that connects to the green wire in the front half of the plug for presence of voltage when key is to Accessory. You can use that bolt that holds the kick panel clip to the body for a ground. Works great. Post back if you need help on how to do that. And yes, I'd like to see pics of both halves as well.

If Pin 16 tests positive, then test the pins immediately adjacent, and see if a nearby pin has voltage, too. Then pull the ACC fuse and see if that voltage goes away at the adjacent pin and at Pin 16. If it does, use alcohol and compressed air or whatever you prefer to clean that sucker up.

OK, assuming that's NOT it, once that's done, reconnect IL1 and replace ACC fuse. Now you have to pull that 3F plug under the dash. Sorry. We need to know if short is between Body ECU and Center J/B or between Center J/B and IL1, or possibly inside Center J/B. If tails light with 3F pulled, it's between 3F and the Body ECU. To rule out the Center J/B, if the tail no longer shorts to ACC with 3F pulled, then take a paper clip or piece of copper wire and jump Pins 13 and 17 (both green wires) in the 3f plug and test again. If the short does not come back, issue is inside Center J/B. If it does, it's between 3F and IL1.

Getting closer. It's narrowed down to about four feet between the Body ECU and the kick panel.

 

[SteinRunner]

Hmmm. Dielectric grease would not be an issue. But you never know if some nimrod used petroleum jelly instead. Dielectric grease does not conduct, petroleum jelly does and would really screw things up..

Do you have a meter or test light? I'd like you to test that PIN 16 that connects to the green wire in the front half of the plug for presence of voltage when key is to Accessory. You can use that bolt that holds the kick panel clip to the body for a ground. Works great. Post back if you need help on how to do that. And yes, I'd like to see pics of both halves as well.

If Pin 16 tests positive, then test the pins immediately adjacent, and see if a nearby pin has voltage, too. Then pull the ACC fuse and see if that voltage goes away at the adjacent pin and at Pin 16. If it does, use alcohol and compressed air or whatever you prefer to clean that sucker up.

OK, assuming that's NOT it, once that's done, reconnect IL1 and replace ACC fuse. Now you have to pull that 3F plug under the dash. Sorry. We need to know if short is between Body ECU and Center J/B or between Center J/B and IL1, or possibly inside Center J/B. If tails light with 3F pulled, it's between 3F and the Body ECU. To rule out the Center J/B, if the tail no longer shorts to ACC with 3F pulled, then take a paper clip or piece of copper wire and jump Pins 13 and 17 (both green wires) in the 3f plug and test again. If the short does not come back, issue is inside Center J/B. If it does, it's between 3F and IL1.

Getting closer. It's narrowed down to about four feet between the Body ECU and the kick panel.

This is great. Again, really appreciate it. As irritating as it can be I actually (in a strange way) enjoy digging into this stuff.

There's a photo of the male end of the plug below, I'll try to get the female end this evening when I start digging back into it after work. I honestly have no clue what's on it, but it looks pretty gross. I assume I wouldn't want to dowse the plug in alcohol, but use pads to clean it up, then use compressed air to finish off the job?

I have both a test light and a meter and I'll process the above test this evening.

 

[SteinRunner]

This is great. Again, really appreciate it. As irritating as it can be I actually (in a strange way) enjoy digging into this stuff.

There's a photo of the male end of the plug below, I'll try to get the female end this evening when I start digging back into it after work. I honestly have no clue what's on it, but it looks pretty gross. I assume I wouldn't want to dowse the plug in alcohol, but use pads to clean it up, then use compressed air to finish off the job?

I have both a test light and a meter and I'll process the above test this evening.

Update:

I did the test you said to do. Pin 16 and the Pin directly next to it both had power with the key in accessory. After pulling the accessory fuse I got no power to either. I went ahead and cleaned up the male and female ends of the plug. I'm waiting on them to dry entirely and then I'm going to re test.

 

[SteinRunner]

Update:

I did the test you said to do. Pin 16 and the Pin directly next to it both had power with the key in accessory. After pulling the accessory fuse I got no power to either. I went ahead and cleaned up the male and female ends of the plug. I'm waiting on them to dry entirely and then I'm going to re test.

Problem still exists after cleaning IF1, moving on to 3F. Will be sure to let you know what I find.

 

[TheDurk]

Cool.

Is 3F still pulled? If not, pull it and do the same test.

Assuming you have pulled it, or get the same result when you do, even if the cleaning does not resolve it, you have narrowed down the short to between 3F and IL1 on the green wire. That's only about 4ft of run. I can't help you any more because that's a straight shot. No plugs or junctions. So you have to find the fault following the green wire with the old Mark I eyeball. You probably need to pull the glove box to do that. Somewhere there is physical damage or an after-build wire tap that's messed up.

In the worst of worlds, you can't find it so you cut the green wire close to those plugs and run a new one between the cuts.

Good luck. You're close.

 

[SteinRunner]

Cool.

Is 3F still pulled? If not, pull it and do the same test.

Assuming you have pulled it, or get the same result when you do, even if the cleaning does not resolve it, you have narrowed down the short to between 3F and IL1 on the green wire. That's only about 4ft of run. I can't help you any more because that's a straight shot. No plugs or junctions. So you have to find the fault following the green wire with the old Mark I eyeball. You probably need to pull the glove box to do that. Somewhere there is physical damage or an after-build wire tap that's messed up.

In the worst of worlds, you can't find it so you cut the green wire close to those plugs and run a new one between the cuts.

Good luck. You're close.

I just finished up testing this A.M. when pulling 3F the issue goes away.

After jumping Pin 13 and 17 the issue is still gone. Am I safe to say the issue is inside Center J/B. Based on everything you've been saying it seems as though this is the case or do you think further testing is warranted. With 13 and 17 jumped the issue with pins adjacent to pin 16 having power in IL1 is gone as well. If it is Center J/B I find myself wondering.

A why would this unit go bad

B can I replace the whole piece

Again, you've been beyond helpful. I would probably be stuck with a $800 plus mechanic bill if it weren't for you.

Really do appreciate it.

 

[TheDurk]

I just finished up testing this A.M. when pulling 3F the issue goes away.

After jumping Pin 13 and 17 the issue is still gone. Am I safe to say the issue is inside Center J/B. Based on everything you've been saying it seems as though this is the case or do you think further testing is warranted. With 13 and 17 jumped the issue with pins adjacent to pin 16 having power in IL1 is gone as well. If it is Center J/B I find myself wondering.

A why would this unit go bad

B can I replace the whole piece

Again, you've been beyond helpful. I would probably be stuck with a $800 plus mechanic bill if it weren't for you.

Really do appreciate it.

Your instincts are right. The J/B itself is unlikely to fail.

I sorta misspoke. The short came from inside the Center J/B TO the TAIL circuit, but the fault isn't actually THERE, in all probability. If you look at the circuit diagram for the Center J/B on p.27 of the Relay Locations link, all the J/B does is connect Pins 10-20 of 3F to each other. So what is probably happening is that some wire other than 13 or 17 is picking up the ACC power and passing it on to all those other pins. These are probably things like the glovebox and dashlights and I don't know what else. What we have done is rule out the TAIL circuit as the problem. It's some other circuit tied to TAIL. Hey, we had to start somewhere.

Sorry, but this is going to take some more work. You need to do two things. Pull 3F, and test each of those pins in the bottom row for 12V+ voltage with key on to ACC. Then you should test any one (remember, they are all connected inside) of the matching holes in the Center J/B the same way just in case it really does originate from inside there (I doubt it). You picked a lousy circuit to have a short in. Those green wires go everywhere.

Hopefully you can report back to me with a single pin number (and please get the wire color it connects to--but it's probably probably green again). Then I have the minor PIA job of going through the EWD to try to figure out what that connects to so we can trace it. The Overall EWD is a pain to read but it can help us here.

You're doing a great job. I wish everyone I helped could work with me as well.