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Tail Lights / Parking Lights - not working

145K views 37 replies 20 participants last post by  mitchsusername 
#1 ·
I have an '04 3 which has been intermittently having issues with the instrument panel not going to "night time mode" when I turn the headlights on. I've discovered that this is probably connected to the parking lights and tail lights. I checked to see if either the parking lights or tail lights were having troubles, and they are not lighting up.

I checked the appropriate fuses, so my question is - is this more than likely a problem with the switch on the steering column, or a problem with a relay, which I understand means a new body control module (under glove box).

Is there a way to test the switch? If I replace the BCM, which I have located with correct part number, does the dealer have to touch it, or is it plug and play if I get the right one?

Any help is appreciated.

Thanks,

Brawndo
 
#2 ·
I would first check contact at light switch.
When TNS OFF, continuity is A-E
When TNS is ON, continuity is A-B-E-K

If switch is fine, then possibly TNS relay.
TNS relay is built-in at PJB, you can purchase PJB but it's pricey...

You don't need dealer to install, if you get right PJB and transfer all fuses, connect back all connectors.

I hope it's not TNS relay,,so pricyey replace PJB
 
#3 ·
Forgive my ignorance, can you translate "TNS" and A-E and A-B-E-K

I guess I should add that the problem (dash lights portion) started off intermittently, and has since become consistent every time. I can only assume that the parking and tail lights are triggered were also intermittent. Never made the connection until today.
 
#4 ·
TNS is name of wire system that related to parking, tail light, interior illumination switching.
TNS relay triggers when you turn parking light ON. (When this relay is ON, parking lights, tail lights, interior illumination comes ON, dims)

A-E and A-B-E-K is continuity check terminal of headlight switch.

TNS ON means
When you turn switch one notch(parking light ON=TNS ON)




If switch isn't making proper contact, TNS relay won't triggers.


But if switch is fine, and still have issue, then, possibly problem at TNS relay that are built-in at PJB
You can't replace only TNS relay unfortunately, so you need to source entire PJB relay/fuse unit.
(I believe what you calls BCM is PJB( relay/fuse unit under glove box))
 
#5 ·
Have you been able to solve this issue yet? I have the same problem and I noticed that I i tap the PJB they come back on. Sometime I need to hit it harder than others. I took the whole dash apart and tracked it to there. I check the connectors and didn't notice any issue so I figure it is the PJB. I want to try and clean the connectors first before I get a new one but I was hoping you found a solution to this problem that may help guide me in another direction. Any luck?
 
#6 ·
My solution has been to keep a long screwdriver tucked just under my passenger seat and when I notice the Green Dash light go out, I tap the PJB and the lights come back on, like magic. I am probably going to try and locate a replacement PJB, since this is getting old. Kind of silly for what is probably a $6 relay, but Mazda doesn't make things easy...
 
#35 ·
My 2004 Mazda 3 hatchback has gotten to the point where a really hard slap is necessary, sometimes up to 30-40 slaps. I use an old running shoe, holding it by the toe end and slapping the heel against the left side of the passenger seat console (presumably this is the PJB location).
 
#7 ·
Hi upashi,

Thanks for your helpful contribution to this thread. I am having the same troubles as the original poster, but my connector at the headlight switch is different than the schematic you posted. I have an 05 Mazda3, with standard headlights (no auto on, no hid, etc etc). My connector has six pins in one row, and 4 or 5 on the other row. Is there a schematic available, with the testing procedure as well, for the 2005?

Thanks again,
Jerry
 
#9 · (Edited)
taillights, dashlights.

My taillight, dashboard are not functioning properly.

Duel bulbs have been replaced(work when brake is applied).
Fuses have been checked.

Headlight switch unit by steering wheel has been replaced.

The most interesting thing I've discovered is the taillights and dashlights will function early in the morning when the weather is cold and frosty, and will also work
Intermittently when I hit the side of the dash board with my hand.

I've removed most of the dashboard and plastic, and initial diagnosis suggests the problem is with the fuse box unit, or the wires Running from it.

I will try changing the fuses related to the taillight/dashboard for brand new ones

Any ideas?
 
#10 ·
An update....if anyone cares.

So my problem is like due to a faulty taillight relay, which is integrated into the PJB(passenger junction box). I have bought a 2nd hand one off eBay with the exact same part number.

I've read that once the new one is installed it MUST be reprogrammed by ONLY a Mazda dealership.

A service man at The Mazda dealership in Lexington, ky, told me they won't touch the 2nd hand PJB, because it may or may not be faulty.

So basically their take on changing fuse boxes like a pjb is you must first buy one from them($900). Then pay them an extra $150 for labour/reprogramming cost.

So I seem to be stuck between a rock and a hard place😖
 
#36 ·
An update....if anyone cares.

So my problem is like due to a faulty taillight relay, which is integrated into the PJB(passenger junction box). I have bought a 2nd hand one off eBay with the exact same part number.

I've read that once the new one is installed it MUST be reprogrammed by ONLY a Mazda dealership.

A service man at The Mazda dealership in Lexington, ky, told me they won't touch the 2nd hand PJB, because it may or may not be faulty.

So basically their take on changing fuse boxes like a pjb is you must first buy one from them($900). Then pay them an extra $150 for labour/reprogramming cost.

So I seem to be stuck between a rock and a hard place😖
So to finally address this issue.... this worked for me and IT FIXED MY PROPLEM. You can check our my Mazda3 3 by my Instagram, ugotmail56. I have a 04 Mazda 3 hatchback 2.3, A/T, Fog lights, no sunroof, manual seats, power windows and power side view mirrors, NON adjustable headlights * for the life of my vehicle, I never used the key fob remote as I never received one from the dealership, so I don't know if what I mention below will work for those of you that have that remote unlock/lock feature.*. .

I had issues with the taillights going out, like people are describing here. The part number for my junction box (JB) was BN8B 66730 C. I went to the junkyard and found both, a 2004 and a 2005, both were the same trim as what I described above with the exception of the 04 Mazda, which had adjustable headlights. The part number for both the 04 and 05 was BN8B 66730 F. This model had 1 extra pin, which I figured was for the adjustable headlight controls, although the 05 did not have that feature, I take it, it was a lot faster and cheaper to use the same junction box for the later models as the pin would simply just be there not connected to anything...


anyways...

I went and purchased it for 30 bucks. Before I installed it. I recheck my JB, and sure it enough, it did it again. I hit the Jb and my tail lights began to work. I disconnected all the connects and compared both. Like I mentioned above, the only difference was the extra pin. I reconnected everything back. Got a trouble that states that the vehicle lost connection to JB. Deleted trouble code and everything worked. radio, power windows, all headlights, fog lights, and FINALLY my TAIL LIGHTS!!!!. Vehicle drove fine, no transmission issues, no ignition reprogramming. Again, I never had nor used the remote unlock and lock feature, so if you do have that feature, take caution.

TLDR: replaced my BN8B 66730 C JB with model BN8B 66730 F and my tail lights are finally working again.
 
#12 · (Edited)
I myself am having the same exact issue. The best option i found for myself is wiring a 12v with key on power (i used the Cigar source) to the 7.5 fuse using a fuse tap. So when i have the key on i can then use them as normal. The problem is in the Fuse box itself and a replacement is hard to get at a reasonable price.
 
#15 ·
I posted other related thread, but if only TNS relay sticking problem, I think you can bypass it to duplicate its function mostly.



All wiring arrange can be done right at PJB

TNS relay's 30 is at J-01 connector terminal F
87 will be split to

Interior illumination J-03 terminal H Which is fused 7.5A

License plate, parking light
J-01 K J-05 AB fused 7.5A
J-01 AC J-05 G Fused 7.5A


To trigger relay, you can extract signal from light switch which also can be find at PJB conveniently.
J-03 terminal I

As long as you bypass those lines, you should be able to copy circuit. Bit of wire work but better than not working relay or paying for entire new PJB
 
#19 ·
Unfortunately, no information about inside of PJB how circuit is lay out...

So you must trace lines, but corresponding terminal should give you idea which relay is related.


or just replace them all with equal spec relays.


Are those reflow SMD? or thorough hole type?
 
#23 ·
i found this thread After the fact, i personally dont see how the relay can be replaced with another, because its 3 boards soldered together, im new to soldering, so i may be wrong, but i dont see how it can be desoldered when the rear of the board is covered by another

This, a rattling engine and blown 3rd gear are the reasons i got my car so cheap, i drove my car first night after switching tags over, and learned of this Light issue, i stayed up LATE figuring out why the dash n tail lights wouldnt work, so i found people saying "give it a good whack" i smacked the crap out of it, and sure enough, my lights came to life........ Sourced another about 100 miles away, went and picked it up, swapped it out, and its good to go, no programming needed

i was a bit worried i had walked into a nightmare, im glad it came out to be something so simple
 
#24 ·
I have the same issue with my '05. I didn't notice until after I did the Duratec swap since I mainly drive the car during the day. A light tap with a snow brush and the lights work. SMFH, what a POS design.

For those that have swapped out the PJB, was the replacement from a car with the same type of transmission you have in your car (i.e. manual to manual) or does it matter?
 
#28 ·
Well, my replacement PJB with the same part number didn't work. While the car started with the replacement box my high beams wouldn't work, the e-brake light stayed on and I couldn't get the car to go into the key fob program mode. I was trying to fix the car before selling it so now I'm just going to tell the buyer the issue and drop the price a little. I've rebuilt this car from the ground up and it slays me that something so simple yet important hasn't been addressed (my version of a rant).

I am going to call Mazda in the morning and discuss the issue with them because this is BS. This is a known issue and they've known it for some time. It probably won't do much good, but I want to hear what the service manager has to say.

Anyhow, I'm meeting the buyer tomorrow so this will likely be my last post and the last Mazda I ever own...I'm going back to Subaru as fast as I can.
 
#29 ·
something tells me you either A. didnt do something right. or B. you were given a faulty unit, but im leaning more towards A. misdiagnosing a problem incorrectly will drive people crazy, i coming from a Cursed Honda civic, am Absolutely satisfied with my 04 mazda 3 fusion swap, much better vehicle than i anticipated, and whoever previously worked on the car was inexperienced, i purchased my car for a deal, because of the PJB problem, rattling engine, and blown 3rd gear, and had to cut the inner tie rods in half to get the outers out, then i replaced both sets and put it back together properly, the wrong tools, approach and technique make a worlds difference in how a problem is solved
 
#32 ·
OK, I know this an old thread, but I had something weird happen. Per the original problem, tail lights and dash lights going off and on randomly, off more than on, and many times per short trip, I took a chance and ran a fused positive wire from the battery back through the body to the trunk, cut the wire to the tail lights and wired them direct with a switch under the dash to turn them on. Worked fine, just still had the dash lights going off and on randomly, as well as the front running lights, but it got me by legally for a while. Then two weeks ago I got brave and reconnected one tail light wire to backfeed current to the dash and running lights. After just one trip backfeeding this way, my fuse box/relay seems to be working fine again. I haven't had to use "the switch" to turn them on in many trips now, they come on and stay on! I have no idea how/what this did, but I like it.
 
#37 ·
I've just addressed this issue with an '04 Mazda3, 2.3L I bought for my daughter to drive to college. The car was owned by her friend, who kept something in the car to bang on the passenger side junction box (PJB) when the taillights didn't come on. I attempted to fix it by ordering a matching PJB from ebay. The replacement functioned but had the same problem, so I sent it back. The relay inside the PJB is called the TNS relay. TNS stands for taillight/number/side and provides power to the taillights ( & license plate) as well the gauge cluster. On my car, there is a small black wire with white stripe (B/W) running from the headlight switch to the PJB. It enters the PJB through a large connector on the top side, left. When the headlights are on this TNS control wire is connected to ground which activates the TNS relay and powers 3 circuits; right taillight, left taillight and illumination (gauge cluster). On my car these are fuses F46, F81 & F82, 7.5A. Power for these circuits enters the PJB on a large pink wire with a blue stripe (P/L) before passing through the TNS relay. The P/L wire enters the PJB through the large connector on the top side, right.

I was able to bypass the TNS relay using an external 30A relay and connecting the coil across the wires B/W & P/L. The power for the relay was attached to the wire P/L and the output of the relay was fed through 3 external fuse holders and the 7.5A fuses removed from the PJB. The output was then fed back into the 3 fuse sockets on the load side of the fuse using just one lead from the fuse extender. Each fuse socket has a source side and a load side. In my case the load side was the lower one on F46 & F81 and the upper one on F82. The fly leads must connect to the load side of the fuse sockets because the internal TNS relay will still be connected to the source side.

These wires/fuses may not apply to all models/years. Before attempting this fix, test with some wire piercing leads and verify that the control and power wires are correct. Remove the fuses one at a time to verify that they are the right ones and probe the fuse sockets to verify the source and load sides of the sockets. There is a risk that you will damage the PJB so be prepared to get a replacement if things go wrong.

Good luck!

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