Mitsubishi released a TSB mid-2006 that addressed a worn input shaft on the transmission as being the root cause of the P0300. The first step is to get their latest P0300 reflash. If the car is still triggering the code and meeting a few other criteria (i.e. full operating temp while cruising at freeway speeds), they're supposed to rebuild the transmission and replace the input shaft with an updated part along with the input half of 5th gear.

 

There is no cure. Learn to live with it or replace your ECu with a standalone. Sorry to tell ya.
I have it on and off for 3 years and there is absolutely no drivability issue with this code.
Hoping to try ECU+'s new firmware to see if that would help. But I am not hold my breath :}

 

There IS an easy fix. I had this code almost a year ago. I would disconnect the battery and about 2 days later the CEL was back. Go to the dealer and get the LATEST reflash. I did this and did not have a CEL in about 10 months now. The initial dealer reflashes did not work but the new ones do from my experience and others I have read on here.

The bad news is if you have a flashed ECU you will lose your tune. So if you do just buy a creader and dont waste time with plugs and such as that is usually only a very temporary solution from what I have read. Just my thoughts though...

 

The Mitsu reflash doesn't work in a number of cases. My P0300 was held at bay for about 2 months, but has since returned. Others don't last 2 miles. WORKS integrates the Mitsu flash with our Brain Flash for all of our customers who've had their tunes flashed over by the dealer.

The only true fix we've encountered has been replacing the worn input shaft.

 

+1 reset the ecu and drive on the highway do like 80+ and if the light come on then it the tranny or shaft

 

I had this annoying problem for months on end. Finally about 3 weeks ago, I changed the spark plugs and the car doesn't do it anymore. I drove it hard, and cruised at 80mph for a while to make sure letting off a bit, and giving it a bit gas to try and get it, but it was fine.

Went from the BPR7EIX plugs gapped at .026 then .022. Finally changed to the BR8ES plugs gapped at .022 which is what now works. So far so good.

Heard ignition amps like the Hyperforce or HKS DLII work for it, but they can get pricey.

 

I'm loving the fact that virtually every problem I've had that should be covered by warranty has started happening around 80k+ miles. I can't wait to pay for work on a problem that's affecting tons of people with all kinds of varying mileage meaning mileage has nothing to do with it. That won't stop them from taking my money and smiling though.

I'm all stock, 94k miles. New plugs, wires, cores, tranny fluid. Sickening really. I do tons of driving on my days off and it's ruining all the fun since roads outside of the city usually have that perfect speed limit that keeps you right in the SES 0300 throwing range. Incredibly annoying.

As for saying it doesn't affect driving, one has to wonder the long term effects of constant misfires/fuel cuts/etc on engine wear and a flakey accelerator at speed is not the most comfortable feeling in the world. If I can drive 15 other random cars without any issues at all when pressing the throttle and this car misfires or whatever it's doing at random, how can anyone argue that it doesn't affect driveability? Driving without any confidence in power delivery on the highway is not the way I enjoy driving.

So the "might fix it" fixes are:

Dealer reflash
CReader (although this doesn't seem to address the issue since I get a stutter and then the SES not the other way around so clearing the code is simply a visual annoyance fix)
Rebuild or new tranny
Standalone ECU?

Am I missing anything? Did I mention this sucks? heh

 

^ My car, on the other hand, does NOT exhibit any type of studdering or missing AT ALL. the light comes on every so often but that is just it. I would agree with you had my car acted differently.

 

This code is actually harm performance of the car, it's not just anoying. When I'm at the drag with this code on, my car ran like sh*t. Reset and it's ok again.

 

How does a worn input shaft cause a random engine misfire code?

 

The signal comes off of timing the crank shaft position sensor. The brains that figured this out knew that the only thing that could cause a sudden change in crank rpm is a misfire. In the real world it seems that other things, things not related to emission problems, can change crank rpm such as slop feeding back from the drivetrain.

What makes this confusing is that some people really do experience misfire and the code is there to tell them. So, they replace spark plugs and post that as the fix. The next person has a tranny problem and gets the same code. No amount of spark plug changing is going to help the owner with the tranny problem.

 

Is it true that the 03 ECUs are more sensitive (i.e. more likely to throw) to this code?

I've had this ever since I went back to the stock ECU (from DSMLink -- 2G ECU) and attributed it to the 272s and slightly lopy idle. Is that not the case? I just naturally assumed that 272s would result in this code.

 

It has more to do with the fact that the '03 tranny uses a different input shaft, which was "upgraded" with the '04 model year. The '04+ models do have some P0300 issues (and corresponding ECU updates from Mitsu), but not to the extent the '03 models do.

 

So I have an 03 with 47k miles... I have had a reflash and I still get the code. For me I get a constant misfire every five seconds...

Literally every five seconds on the highway. Sometimes I can accelerate slowly/keep the same speed and it won't studder.

So if I get a creader is it just going to clear the code? Or will it stop the constant, horrible, (makes me want to blow up the car) studder?

Any info would be great.

BTW someone said earlier that Mitsu will rebuild a tranny. Is this for the 60k warranty? So this would include me correct. Or is this a complete recall and includes everyone with the problem.

 

Gsxtremedsm, I would try changing out your plugs. Your stumbling sounds like a legitimate misfire.