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PJB / BCM Part Numbers?

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29K views 13 replies 8 participants last post by  Euri2004  
R
#1 ·
Just bought my first Mazda3, a 2004 S 2.3 MT Hatchback, and love it, except for one problem. I’m having the intermittent TNS relay issue: No tail lights, parking lights, dash lights when I turn the headlights on. When I tap on the PJB, the lights come on, so I'm 98% sure it's the TNS relay.

I know it’s possible to wire in another relay to bypass the faulty TNS relay, but I decided to try to swap PJBs first. So I got a salvage PJB on ebay, hoping for a simple plug-and-play swap with no reprogramming necessary. My original PJB part number is BN8B-66730-C and the one I bought is BN8B-66730-J. I had assumed that the J model was just a later version of the same part, but I later read that the J model is for Canadian models with running lights. Can anyone confirm what the different letters mean, and how critical it is for a successful swap out?

Thanks,
Ray
 
#2 ·
Arggg... I can't tell you how many threads on the subject of the PJB/BCM I have read only to find them end with no answers.

My granddaughter's Mazda 3 i has this problem too. I can easily get the same part number (BN8B-66730-C) but can't find anything definitive about the replacement and whether dealer programming is required or not. Some say absolutely yes and others say absolutely not. My assumption is that if the donor car has the exact same features/options then, assuming that the p/n is the same, it should be a simple plug & play. Have you found out anything on this?

Also, you say that you "know it’s possible to wire in another relay to bypass the faulty TNS relay". Have you run across a procedure for doing this that gives the relay p/n and wire colors for doing it? If so, would you mind sharing?

Here's hoping that you set up email notification when you posted this...
 
#4 · (Edited)
Lots of People are having problems with their internal instrument lights/ taillights/license plate lights cutting out intermittently. After changing bulbs, the light switch, and using a bulb current tester, along with wire diagrams, I tracked the problem down to the intergrated 'taillight relay' located behind the gloove box, in the passenger junction box(pjb). The fuses (80,81 & 46) all looked good. Tapping on the PJB will turn the lights back on sometimes.

The only way to fix this is replace the whole PJB!! & the Mazda dealer will charge you $1000+ for the privilege :(

So for my 2004 Mazda 3 sedan, I bought a PJB with the exact same part number
(BN8B-66730-C) from eBay. Disconnected the battery. Unplugged the 6 connectors on the PJB and simply plugged in the new one.(make sure the connections are snug in their sockets, pull the latches all the way open, before inserting).

All lights are now working, A/C comes on straight away, even central locking works.

NO reprogramming or flashing required.
Cost : 100 or so buck

Oh you're welcome :wink2:
 
D
#6 ·
I have a question...

Do you NEED to perform the configuration procedure shown here?... oops, it won't let me post the link because I am a first time poster

The link says "Replacing the PJB without performing the configuration procedure will result in system malfunction."

You make it sound pretty easy (plug and play) with no programming.
I want to take your word for it and proceed but what kind of "malfunction" would I possibly be looking at.
Someone in the other thread listed above said that after the swap their auto function on the headlights doesn't work anymore.
Like him, I can live with that (as long as my headlights will TURN OFF!! lol).
I just don't want to create more issues.
I know this is an old thread so if you reply I am very grateful, thanks in advance.
 
#5 ·
Hi guys,

I've been having the same TNS relay issue for a pretty good while now. Up until recently I've been using the hit-the-BCM-with-a-screwdriver method but it's becoming increasingly less reliable. I want to do a BCM swap, but the closest part number I can find is off by one letter. My car has the number BN8B-66730-E and the closest one I can find online has the number BN8B-66730-F.

Is this part going to be plug and play since it's pretty close or should I hold off until I can find one with the exact same part number?
 
P
#7 · (Edited)
I know I'm reviving an old thread, but I thought I would add my experience, and hopefully help someone else with a similar PJB issue. Picked up an '04 Mazda 3 hatchback, and noticed after the sale that the tail lights, license plate lights, and interior illumination weren't working. Did some research, and with the help of this forum, narrowed it down to the TNS relay inside the PJB. Without access to the backside of the circuit board to unsolder the relay, I came up with a relatively easy workaround.
I didn't want to buy a used PJB module, or attempt to separate the two circuit boards. Instead, I carefully removed the old relay using a dremel and thin cutoff wheel, leaving a portion of the copper legs soldered to the board.
I bought 5 relays on Ebay, and waited the week for the slow boat from China:
5Pcs CQ1-12V Power Relay Automative Relay 20A 12VDC 5 Pins | eBay
I removed all the plastic bits to allow for a good solder joint and then soldered the new relay in place on the outside of the board. The new relay sits about 1/8" off the board, which is fine.

Total cost = < $20 (and I have 4 spare relays in case another one goes bad)
Hope this helps someone out there.
 
E
#14 · (Edited)
Same as the OP, I just swapped my PJB for one I purchased on eBay. I went out on a limb and ordered one that was the "J" version instead of the "C" version the car originated with (BN8B-66730-C). I noticed that the J version has two more fuses that the C version does not: F38 and F74 (seat warm). All worked perfectly (luck?), no issues with the keyfobs or any other functionality. I noticed the A/C button responded more solidly than before; it would normally not kick on/light up for about a few seconds.

I feel better that now I at least have a backup and just ordered the relays that picassodavinci noted (much thanks!) and will try and replace it once it comes in.

Also, I just went onto NHTSA and reported this as a safety issue. Maybe if enough of us do the same they will open up a case with Mazda about this.
 
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