165 - Tail Light Problem

MisterKrazee

New member
Yesterday I bought a 165 with a JDM 3S-GTE swap from a 92 MR2. It's having issues with the tail lights not working. I have gotten the STOP lights working. The white power wire going under the fuse box in the engine bay was unplugged. This thread helped with that problem... http://www.alltrac.net/phpBB2/viewtopic.php?f=21&t=30356&hilit=brake+lights
I've gone through several other threads on here and have come to a point where I'm not sure what to try next.

Per this thread... http://www.alltrac.net/phpBB2/viewtopic.php?f=22&t=6328&p=57142
When I jump the two 15 amp fuses my corner, guage and license plates light up constantly. Even when the key is not in the ignition. This definitely is an issue. The headlights function as well, this may be normal, not sure.

I have also tried jumping the tail light relay according to that thread with no progress.

All fuses and bulbs appear to be good.

The yellow lamp failure box has "bad" written on it. I'm not sure what the deal with that is or if it is actually bad and contributing to the problem.

Any help would be much appreciated.
 

Dracov

Member
If the yellow box is hosed that could explain the behavior. They are susceptible to water damage because of their location. Mine goes wonky after it's been raining heavily but it clears up after everything dries off. Try to see if you can get a known working replacement
 

MisterKrazee

New member
That's pretty much the last thing I have to check before I start digging into the fuse box/wiring harness. I found some info on bypassing it that I will try for testing tomorrow. If that ends up working I'll source a replacement. I'm ready to get this thing back on the road. Fingers crossed!
 

88gt4DE

Active member
Looking at the wiring diagram ... power comes into light failure relay at terminal 10 which is green. comes out of light failure relay and goes to lamps on the light green wire terminal 4 . Vehicles that did not have the failure relay , this wire is connected. Hope this helps yer efforts. If ya cant find a relay quickly you can prol run a fused jumper in between those wires and it will work for ya temp.... 8)
 

MisterKrazee

New member
I tried bypassing the Light Failure sensor with no luck. At first neither the STOP lights or tail lights were working. After scratching my head a bit and looking through the BGB again I realized it was a female plug and I was counting the pins wrong. :bangshead:

It was a little frustrating looking up how to bypass the Light Failure Sensor. Most info I found was for Supra's and Camry's. Apparently some of them use the same exact sensor, but the wire colors are different than the AllTracs. I finally found which pins supposedly needed to be jumped together.

Jump 4 and 10 together.
Jump 7 and 1 together.

At that point I had STOP lights, but still no tail or corner lights. So, either I still have the pins wrong or my problem lies elsewhere.
 

MisterKrazee

New member
Okay, so I have good news and bad news. The good news is that those are the correct pins to jump to bypass the Light Failure Sensor. The bad news is that I still have a problem.

It appears I have a power issue in the driver side kick fuse box. After bypassing the Light Failure Sensor, I jumped the 15 amp Stop and Tail fuses according to the thread I linked to in my first post. At this point all lights worked, including the tail lights. Although they are still on constantly.

Any ideas as to why this would be?
 

MisterKrazee

New member
Made a little more troubleshooting progress tonight. I began checking voltages at the fuse box starting with the tail light relay. The multimeter I was using is kind of crappy so I can't give exact voltages, but I can compare it to what I measure from the battery and know if I'm getting full voltage or not.

With my light switch turned off I get full voltage on the fuse box when I measure the top two connectors taht the tail light relay plugs in to. I get no voltage on the bottom two. I would think this is normal.

With my light switch turned on I get full voltage across the top two connectors still, but only half voltage on the bottom right connector. Is this correct, or am I supposed to be getting full voltage here as well?

With the light switch turned on and a new relay plugged in I do not get any voltage at the tail light fuse. If the voltages going to the relay are correct, I'm assuming the connection between the relay and the fuse is bad. Is this connection made by a wire behind the fuse box or just a connection within the fuse box?

My fuse box is held in pretty tight by the wiring harnesses so I would rather not try to get behind it or inside it to check the connection. I feel this could end up creating even more problems moving the old wires around. I have no problem building a small wiring harness utilizing the working connectors on the fuse box, while relocating the tail light relay and tail light fuse off of the fuse box thus bypassing the bad connection. Although keeping everything as stock as possible is preferred.

I guess the main information I need is if I'm getting the correct voltages at the tail light relay. Any other input is appreciated as well.
 

MisterKrazee

New member
I wasn't able to find a solution to the voltage problem, but I was able to get the lights working so I'm street legal. I ended up using connectors and wires to basically bring the tail light relay off of the fuse box. It is still wired through the proper fuse. Since I don't have fog lights i wired the switch into the 12v switched side of the relay. I just have to remember to flip that switch whenever I turn my headlights on, which isn't too difficult since the gauge lights are in the same circuit.
 

88gt4DE

Active member
Good you found the issue though and ran a correction that is fuse also ... I think mine little relay is starting to screw up. If I have the lights on and turn the turn signals on the lights in my HVAC panel start flashing with it ... or they get brighter if I hit the brake. Had the classic water leak in the left quarter glass so I'm sure it screwed that thing up ... It been a few years since the leak and it still does it ... oh well ... :shrug:
 

sefiroxx

New member
When doing electrical diagnostics, find a good power source and ground point that you can
A) verify the meter is working
B) have connection points to use during testing.

Test your meter against the battery to see what system voltage is. (Turn on lights to see what it drops to)

When moving to the symptom area, find local positive/ground points that provide the same reading as the baseline. You might have to move up/down the circuit to find stable points.

A typical circuit has a primary fuse, primary switch (ie ignition), secondary fuse, and secondary switch. A relay utilizes 2-3 circuits. The control circuit is routed through the light switch and is low power/amperage. The headlight switch might control the per power leg on the relay box or the ground leg. The primary power to the headlight is a second circuit that has its own fuse and then routed to the relay. (A third circuit might be fed from the relay for certain applications where power is sent one of two directions pending switch settings.

To test the relay box/holder. You typically need the writing diagram to see which legs are hot and which are the load/ground legs. Test the hot leg to a known ground point (see beginning of post) to verify proper voltage. Engage switches, remove fuses etc to verify voltage. Do the same on the ground/load leg by utilizing the continuity check of the meter , checking the key to the known good ground point.
 
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