New here and need some help, fellas!

I've got an '05 Mazda 3 4dr with some odd fuse/wiring issues.

It started off in February that I replaced the fuse (21 horn 15A) which goes to the horn and brake lights. Since then it has shorted out about every 3 months and now, it wont work at all with a new fuse.

A year ago, one of my headlight went out and I changed both at the same time. In May, my passenger side headlight went out. I replaced that and now the driver's side headlight is out.

Any ideas? Is this a bad ground or a wiring shorting somewhere in the system? Has anybody had any similar issues?

Thanks for the help!

-Adam

 

search on the forum, I know I saw someone with horn issues that was similar to this, and I think it ended up being a bad Passenger Junction Box (PJB) - seems like that is the source of many issues, and has been a majority of the posts i've helped on so far.

Look at http://www.mazda3club.com as well, that's where I recall some other horn issue - like the horn messed with the lights or something to that effect.

 

Thanks for the help!

Its clear I either need to clean the contacts and/or replace the Passenger Junction Box(PJB).

My question is, if I attempt to remove and clean it myself, does the computer need to be reflashed? I would think simply disconnecting the battery, removing it the PJB and cleaning the terminals wouldn't necessitate the computer needing to be reprogrammed, right?

 

You can pull the box out with no issues, though it will reset the cluster trip odometer, and I think you loose clock power - other than that there is no other information lost on the car. It's a good idea to disconnect the battery, but it's not required. I believe that you can swap another one in without reflashing anything either.

How is "Its clear I either need to clean the contacts and/or replace the Passenger Junction Box(PJB)."... take a connector off and have a look first. Some of the wires may fall off in your hand, or similar with the pins - breaking off in the connector if they are corroded apart. If that's the case you'll need some new wiring as well as a PJB, but just have a look at it first and see if there are any obvious isuses with corrosion.

 

I pulled the PJB out and it looks completely fine. No corrosion or rust anywhere. I took the entire assembly apart very carefully and didnt touch anything inside. There was some very light dust, however, which shouldn't make a difference.

Now that I've ruled out the most expensive piece in the puzzle, where do I look to next?

 

Electrical issues are almost always fun. The rule of thumb is to start from either end and work your way back to the other end.
If I understand your post, it's pretty clear you have a open in the circuit somewhere. What you said is you have a new, good, working 15A fuse in the circuit but still no horn or brake lights, right?

Since you think the headlight situation may be related, why not start with the battery cables, making sure they are not corroded, and not just at the battery either. The other ends are even more suspect, as are any engine to body/chassis grounds. Since these are all dry, pressed fit to the cable, pull them all off and make sure there isn't corrosion inside the connectors.
From there, just work your way back to the brake lights, checking everything else in the path.
I know its a time-consuming, often frustrating PITA, as I've been there and done that before myself, but it may be necessary. Sooner or later you'll come across the offending connection.