About 2 days ago I got a catback exhaust system and a strut bar, then yesterday the check engine sign came on. I tried resetting the ECU by disconnecting the batteries but it still came on... I heard that there is a way to use your ECU and it's LED lights to figure out what the specific problem is... I already found the ECU but can't find where the mode selector and the LED lights are... please help me! (1996 240sx)

PS the guy at Meineke said that my rear o2 sensor's out could that be the cause of the check engine light (but I read in an earlier post that the front one is the one that the ECU checks) but the guy at Meineke said my front o2 sensor is still fine... he checkedthe temp. of the pipe between the 2 catalytic converters and the temperature was close to 400 while everything from the cattalytic converter back was only 200 something. He said my converter's gone also I was just wondering what would be the next step for me to take if I don't want to spend too much $.

I was thinking maybe use the ECU to check where the problem is that's why I was asking how to take out the ECU and find the mode selector screw and LED lights. If ANYONE could shed some light PLEASE help... Thanks!

Hello. I just had the same problem. I got my cat back put on and 2 weeks later the check engine light went on. (Do you see something in common...) Go to http://www.240sx.org, Find the "FAQ" on the top of the page. Scroll down on the right hand side and find "ECM, finding trouble codes for DOHC" (I am pretty shure you have a DOHC and not a SOHC). Follow the instruction on how to take the ECU out and test it. (DO NOT DISCONNECT THE ECU!!!) I tested mine and I could not find the RED LED. However, when I followed the instrutions, I found that my check engine light would flash on and off instead of that red led (so use the dash light....) If it is the rear 02, it should flash 7 times slowly, than 7 times fast (which means 77). The consensis is that the Rear 02 is useless. So do not get it changed (according to Nissa...)Hope that helps.As for your cataletic converter, make shure the guy knows what he is talking about. I am not shure if the Canadian cars are the same as the American cars because my cat. is beside the manifold. If you are talking about that round thing with a flange on it that is bumpy, it might be a "Sub muffler" and not a cat. Go to Nissan and have them take out the sheet with the underneath of your car. Most mecanics make that mistake and think this part is really a cat.............so you might not have a "true" cat-back.....but thats okay. Nobody know but us Nissan guys.If I got anything wrong, I have only been in this for one year. So anyone can correct me....

Paul1997 240SX

YES! I solved the problem! I reset the ECU w/o using the ECU. At first I disconnected the batteries for about coupla minutes and then reconnect them, that didn't clear the ECU -- but I disconnected the batteries overnight the next morning the lgiht was gone! My dad (he works w/ computers) says that he thinks it's because most computers have a chip that can store information for several hours in case of a power out (I tihnk most computers these days can store information even longer than a couple of hours)... so by disconnecting the battery all night, the pweor ran out. Note: I had to reprogram all the clocks in my car which is exactly... 2 hehee.

yeah, the ECU drops its codes after 24 hours. you could have done it by turning a screw a few times back and forth, but it's solved either way.