Melted O2 Plug
 

Searched on this and it turned up a few results but really no clear answer. So I got the P0038 code and purchased a new O2 sensor. Went down there today to put it on and the sensor plugs are melted together. Does anyone have any suggestions on how to get around this?

Clarify please. Pic?

The connector between the harness and the old plug has melted into a solid-ish block of plastic.

You don't have too many options here. The cheapest and easiest would be to cut out the plugs completely, being careful to understand which wires are which, and cut off the connector off the new plug, and just wire them together.

The only other real option would be to get the tail end of the wiring harness that leads to the plug, and splice that in so you can have the connectors still.

You would have to replace the whole engine harness I believe, to replace the connector without any splicing.

Thanks for savin the day RIWWP. I was just confused by what he meant. I've never had this problem... Hmm..

Slap me if this is stupid. But could someone use their COBB accessport on my car to just delete the code?

I believe he mean this, see attachment, except mine is WAY worst

Believe it or not, u can pull it out with brute force, the connector melt but they are not exactly bonded together.

U can replace the connector with another connector. I seen them online somewhere.

How does that solve a melted connector?

I think he wants to just delete the code, and leave the melt plug as is.

First I would find out why the connector melted. Either you are missing a heat shield, the connector/wire came unclipped from where it was secured, or you have a bigger problem like a clogged cat that generated enough heat to melt it.

^Yeah, I would be paranoid about the "why?"

in my case, everthing were secured to their location, so I would "assume" it was a clogged cat,

cuz after I saw what happened to the connectors, I dropped the cat and cat back, the front of the cat looks fine, but I found broken pieces of cat in the muffler. so the I think the 3 way cat's rear part melt, flew into the muffler causing blockage, which killed the engine.

I got the car dirt cheap with a dead engine (frt rotor 4.x, rear cannot be measured, too low), so i am not complaining, gonna try to do a complete MT swap. already got all wiring I need, now just gotta source the rest of the small parts here and there.

Im gonna get a brand new Mazdaspeed cat and new muffler and start from there.

Yeah the cat is good. No rattling and can't see through it. I run the car hard and no glowing what so ever. I am assuming the connector broke free somehow and just melted from the heat of the cat? Not 100% sure.

I asked about the Cobb because I know the rear O2 is not vital so thought that could be potentially a very easy solution.

You'll need your own AP because they get married to the car. If someone were to flash your ECU and unmarry the COBB from it, It would revert back to stock maps... leaving you with a CEL again.

So I spliced the wires together and reset the computer. Light went off for .1 miles and then came back on. I was stumped so took it to a shop. They said they traced the electrical and the sensor is good. the wiring is good. But when they got to the ECU the mainframe and transistor were fried and need to be replaced. They said it would be $1400 to replace this. Does this make any sense? The only code on the car is P0038 but now my entire mainframe, that is what he is calling it, needs to be replaced. The car runs perfectly. Just has a check engine light and wont pass smog because of the P0038 code.

Yes, I had this happen in another car. Basically the internal resistor that takes incoming 12v and drops it to the 5v signal for the O2 sensor is fried, probably because of damaged wiring earlier. Yes, replacing the ECU is the only real solution, since the damage is inside of it, on a board.

There are cheaper options, but you have to be very careful about what ECU you get if you get one used, you need one at least of the same engine, generation, and region that yours is, though if you can get one of the same year and trim, that would be best. You will need a dealer to program the ECU into the various components correctly, since every other module in the car is specifically looking for that ECU's serial.


The only other possibility is to basically find replacements for the damaged board components, and have them added in-line between the ECU and O2 sensor. It may not work though. Someone with more electrical knowledge than I would have to help out with exactly what electrical components you would need to try.

What kind of detrimental effect does this have on the car? If it is something I cannot immediately fix will it cause significant problems to the vehicle?

Assuming that this is the rear O2 (I don't see you specifying which, just implying), then no harm to the car, just an inability to pass OBD2 inspection. I ran without a rear O2 sensor (and catless) for years.


Edit: Though yes, you could get an AccessPORT or MazdaEdit to block those codes from ever showing.

Yes sorry. It's the rear O2 sensor. And I was thinking of doing the COBB instead but wasn't sure that would work. I figure if I am going to spend some money I might as well do a mod that will give the car a bit more efficiency and power.

Yup. You will have problems if you ever sell the car and don't include the flashing device and it's tune, but you should be fine that way.

You don't note the year or mileage, but it just occurred to me that the ECU is one of the major components covered by the 8yr 80,000 federal emissions warranty, so if you are under that, you might be able to get the ECU replaced by a dealer for free.

I don't think it's covered. I did have the engine replaced at 80,000. But mazda said the replacement only has a one year 12,000 mile warranty. Which I'm guessing they re-used all the old ECU components.

The car itself is at 106K.

Yes, they would have reused everything but the engine itself, including plugs, wires, harnesses, connectors, etc...

And at 106k, you are out of the 80k emissions warranty. Figured I'd just toss it out there just in case.

Thank you RIWWP for the wise words. I am thinking I will most likely go with the accessport. I've been wanting to get one for awhile anyways and like they say, no time like the present.

Have had it happen numerous times on the secondary O2 sensor when the connector comes loose off the bracket and then gets up against the cat converter during hard cornering. You have to break the plastic connector apart without damaging the wires and connector pins. Most people don't realize that the connector pins are designed to come out of the connector (depinned or depinning) which allows you to replace broken plastic connector housings. It kind of comes down to how good you are at DIY stuff. Once you have the pins out from the melted housing they just slip right into the replacement housing. You have to get the order position right, so make a diagram using the wiring colors or use the OE electrical diagrams to get it right.


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Mark

His issue now is that the prior damage fried/popped the internal resistor in the ECU.