how to install different front seats - with no fault codes
 

Here are tips for avoiding fault codes and warning lights when putting in different front seats. Most of these have already been posted and are known, but I think a couple of them are new - the correct resistance of airbags in front seats, and how to avoid fault codes for the passenger weight sensor system.

I'll describe in two parts, it depends on whether you replace your seats with other OEM Lancer seats, or with aftermarket seats. Disconnect battery before starting any of this.

INSTALLING DIFFERENT OEM FRONT SEATS
Driver's seat should be "plug and play", no issues. Problem on passenger side is weight sensors and related ECU module under the seat, these are uniquely coded to the central SRS ECU in the vehicle. Here's how I avoided this fault code. Take out the complete original passenger seat. The sliders and the seat float and mount on 4 weight sensors, these shiny weight sensors are also attached to what I'll call the bottom bracket. Under each weight sensor, there are two matching nuts. Undo the 8 nuts, then lift seat off the bottom bracket. Attached is a photo of one of the weight sensors, showing one of the eight nuts to undo. Also a photo of the bottom bracket, with the 4 weight sensors and related ECU module still on it. Swap this bottom bracket onto your new OEM seat and install in car. Central SRS ECU sees the original weight sensors and ECU module, so there is no fault code.

INSTALLING AFTERMARKET FRONT SEATS
A couple more issues to deal with. First, to deal with the passenger side weight sensors, keep the bottom bracket described above. You'll need to fabricate an adapter on which to put your new seat rails or new seat, so that the new seat mounts onto the original weight sensors on the original bottom bracket. Fabricating the adapter with flat metal bars is the best way to go.

Also, if you ditch the 3pt belts and only use harnesses, you will have to deal with the belt buckle sensors in the female part of the buckle. I got a couple of "dummy" female buckles with the male inserted in them, secured under each seat, and plugged electric leads to harnesses. Can source these from a junkyard if you don't want to sacrifice your originals. Central SRS ECU now sees both front seat belts as on all the time. There may be an easier way to do this, maybe use resistors instead?

Driver's seat has another sensor - the seat slide position sensor, it controls how the steering wheel airbag deploys - one stage or two stages. Photo of the sensor is attached. Go get one from a junk yard, or keep the one from the OEM seat you removed. Secure to the floor or under your new seat, plug lead into harness. This sensor normally works thus: with the seat slid forward of a certain point, a steel prong or plate covers the sensor and the SRS deploys the steering wheel airbag one stage, based on driver being close to the steering wheel. If the seat is moved backward of that point, the sensor is not covered by the plate, SRS deploys stage two of the airbag, based on driver being further away. So when you secure the loose sensor under the seat, you can choose to have the business side of the sensor either facing or not facing a piece of steel (e.g. your new seat bracket), to choose whether you want stage one or stage two steering wheel airbag deployment. The business side of the sensor is the side opposite the one with the writing on it.

Last but not least - if you put in aftermarket front seats, you will get SRS fault codes for not having the airbags in the seats. I measured the resistance of the airbag in the front seats, it is 2 ohms. Went down to Radio Shack, they had no 2 ohm resistors, but I got two 5-packs of 1/2 watt 10 ohm resistors, one 5-pack for each seat. Connect five 10 ohms in parallel, you get 2 ohms. I connected these to the yellow connectors in the harness coming out of the flow. Central SRS ECU sees two air bags still there.

I think that's everything that enables front seat swaps with no fault codes. Much of this was already known, maybe all of it, I thought it might help to put everything down in one place. But what I had not found on the list when I first looked was the resistance of the airbags in the seats, and how to avoid the passenger weight sensor fault codes.

Now the disclaimer - this all worked for me on my 2008 Evo, but I can't guarantee it will work on all 2008/2009 Lancers/Evos. ALSO, always disconnect battery before disconnecting or reconnecting air bags. And if you store airbags or leave them lying around, bridge the connector with a wire, to avoid stray sparks setting them off.

i could be wrong but once you unplug the passenger seat sensors under the seat you will need to have the seat recalibrated already. i read a while back that some guy just took his seats off to run some wires and as soon as he put the seats back on he had the light come on.

There should be no problem if you first disconnect the battery before messing with the seat connections, and not reconnect the battery until after you have eveyrthing hooked up again. I have had my passenger seat in and out several times with no problems, no fault codes. The only time I got a fault code is when I put in a seat with different sensors/module than the ones that came with the car.

YMMV

I have read here of folks getting the dealer to reprogram and recalibrate for different weight sensors and module. My dealer could not do it. I talked directly to the tech, he appeared knowledgeable and thoroughly trained, and described how/why the fault code would show up again. He claimed that he also checked with Mitsu directly.

Anyway, it then became a moot point for me. I did not want to pay the the dealer again for more re-programming and/or fault clearing experiments, nor trying other dealers in town and have to pay them too, possibly with no joy too, nor to spend any more time commuting to dealer(s). I eventually found the solution I described, the main advantage of which is that it is cheaper because you do not need to go to the dealer at all. And quicker too. And easy to re-install the original passenger seat if/when you want to sell the car stock.

this is extremely valuable information. Thank you very much! BRIDE SEATS here I come!!!

Question.. when you say you wired the resistors in parallel, were talking about grabbing 5 10 ohm 1/2 watt resistors, and connecting the all the ends of one side to one wire, then all the ends of the other side to another wire.. ending up with two leads that you plug into the harness... is that right?

*EDIT. Just soldered the 5 10 ohm resistors and tested it using a voltmeter... resistor came in at 2 ohms! My Drivers side BRIDE seat is installed! no error codes, no airbag lights... The passenger rail is plugged in and the stock passenger recaro is out! Just waiting for some custom fabrication for my lower seat rail so I can install the passenger side Bride seat! Exciting exciting!

so it looks like I spoke too soon :( The airbag light came on today on my way to work.. It took about 4 miles of driving before the light came on... OP, any ideas? I have the resistors alligator-clipped to the harness coming from the floor of the car... The position sensor on the drivers side is zip tied to the bride seat rail...

As for the passenger side, the original bottom part of the rail is intact and plugged to the car.... Currently driving with no passenger seat....

^my "feeling" is that the light came on not because of your drivers side BUT rather your passenger side. as what i mentioned above, once you disconnect the passenger side that's it, you are going to need to visit the dealership unless a bypass can be found.

beetle, i think you might be right.... I removed the stock rails off the seat completely on the passenger side and left everything plugged in though. I also did this with teh battery disconnected. I think maybe the rail tripped the light because its sitting there sensing ABSOLUTELY NO WEIGHT at all...

But if i throw my stock passenger seat back on the rail, i wonder if the light will need to be reset by dealer regardles...

damn it!!!

PS. Found solution to seatbelt bracket.

i just remembered what i had posted a while ago when i did the MR seat swap. From what the tech told me this is how mitsu assumed when they did the airbags. mitsu assumed that 100% of the time a driver will be over 65 lbs, hence no point in turning off the airbags, hence no lights. on the passenger side though is the opposite. once the seat "detects" there is weight on it and is less than 65 lbs the airbags are turned off (light on) BUT when passenger is over 65 lbs then airbags are activated (light off).

just like my previous post i regret that once the passenger seat is unplugged, regardless whether you disconnected the battery or not you are going to pay the dealership a visit.

We need a Genius.
i'm prty sure the one that find how to bypass this sh..t can make some money.
come on guys!!!

UPDATE: This morning, I threw my stock RECARO PASSENGER SEAT back onto the STOCK rail that is chilling in my car.... I didnt bolt anything down. On my way to work... NO AIRBAG LIGHTS, NADA.

Beetle, you were right, looks like the weight sensors need to sense AT LEAST some weight on them in order not to trigger the light. Looks like the 2ohm resistors are doing their job. Will report later when I get more seat time behind the wheel!!!!

This is getting EXCITING again.

Let us know. i'm dying for some serius bride or sparco

great to hear {thumbup} i guess i could have saved $100 by swapping out the sensors underneath my GSR recaros to my MR recaros.

archiebabes is selling some brides but unfortunately he is not local, i would be more than happy to sell my MR seats but the light is also turning me off.

UPDATE AGAIN: Happy to report I'm on day 3 of driving around. I have logged about 60~80 miles in the last couple of days... STILL NO LIGHTS. Looks like its working! ... and this time, my passenger BRIDE seat is fully installed and everything is good to go.

Thanks OP!

Glad to hear this all worked out.

AFAIK and FWIW, there may still be some history of a former error in the SRS ECU, even though the cause of the error is now gone. I may have that too on my car - but as long as there are no #$%%$!@# lights on to annoy me, I don't care!