Check engine light question - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Lilredsx · 05-19-2013, 06:59 AM

I’ve had my 240, a 95 with an auto box, for almost a year and the check engine light has always been on. As money permitted I’ve replaced or repaired things that were messed up on the car. I also took the car to Advance to get a scan to see if I could figure out the reason for the light. The codes pointed to the transmission, and indeed the TPS was bad and the tranny would slam into gear. Changing the TPS fixed the hard shifting but the light stayed on.

Recently I had to take out the exhaust behind the cat, to change out my subframe bushings. In my rush to put everything back together I messed up the stud on the cat so there was an exhaust leak. This Friday I tried to take out the cat to fix the stud and ended up breaking a bolt from the cat to the downpipe. Since time didn't permit I had to drive to work with an open exhaust until I can either get the bolt taken out and the stud fixed or a test pipe or new cat.

On the highway to work, I happened to notice that my check engine light is no longer on. I figured that the bulb must have burned out. When I got a chance, once I was stopped, I turned the car off and then on. All the warning lights lit up, including the check engine light, and then all went out as normal.

So, why would my taking off the cat cause my check engine light to suddenly go out? And funny thing about the cat is that it was straight through. No baffles or anything, is this normal for the 240s?

*fliprayzin240sx* · 05-19-2013, 02:32 PM

Cat could have been clogged up...

Silvia716 · 05-19-2013, 05:11 PM

Cuz of your 02 sensor and you probly could use a new cat too

Lilredsx · 05-19-2013, 05:20 PM

I was trying to find a picture of what the inside of a cat is supposed to look like. There is nothing inside this one at all, it goes straight through.
I found this link and I did not have the shield that he has under his cat on mine, so maybe someone before me gutted the cat.
http://zilvia.net/f/s-chassis/427317...t-install.html

i guess I'll get the bolt and studs fixed and see what it does then.

cotbu · 05-19-2013, 07:34 PM

If you have a front 02 and a rear 02 there is supposed to be a difference in the reading with a cat installed. This is what i think happened, your gutted cat didn't allow for a change in the reading, check engine light on.
when you created a leak, there was a difference in the reading no check engine light. Maybe loooong stretch?

05-19-2013, 06:59 AM	#1
Lilredsx Join Date: Jun 2012 Location: FL Posts: 16 Trader Rating: (0) Feedback Score: 0 reviews	Check engine light question I’ve had my 240, a 95 with an auto box, for almost a year and the check engine light has always been on. As money permitted I’ve replaced or repaired things that were messed up on the car. I also took the car to Advance to get a scan to see if I could figure out the reason for the light. The codes pointed to the transmission, and indeed the TPS was bad and the tranny would slam into gear. Changing the TPS fixed the hard shifting but the light stayed on. Recently I had to take out the exhaust behind the cat, to change out my subframe bushings. In my rush to put everything back together I messed up the stud on the cat so there was an exhaust leak. This Friday I tried to take out the cat to fix the stud and ended up breaking a bolt from the cat to the downpipe. Since time didn't permit I had to drive to work with an open exhaust until I can either get the bolt taken out and the stud fixed or a test pipe or new cat. On the highway to work, I happened to notice that my check engine light is no longer on. I figured that the bulb must have burned out. When I got a chance, once I was stopped, I turned the car off and then on. All the warning lights lit up, including the check engine light, and then all went out as normal. So, why would my taking off the cat cause my check engine light to suddenly go out? And funny thing about the cat is that it was straight through. No baffles or anything, is this normal for the 240s?

05-19-2013, 02:32 PM	#2
fliprayzin240sx Man w/ CTSV & a Car Seat Join Date: Aug 2002 Location: Tampa Posts: 17,998 Trader Rating: (19) Rides Gallery: fliprayzin240sx Feedback Score: 19 reviews	Cat could have been clogged up... __________________ If you think Zilvia has too many assholes... CLICK HERE!!!

05-19-2013, 07:34 PM	#5
cotbu Post Whore! Join Date: Sep 2005 Location: SWFL Age: 47 Posts: 3,318 Trader Rating: (3) Feedback Score: 3 reviews	If you have a front 02 and a rear 02 there is supposed to be a difference in the reading with a cat installed. This is what i think happened, your gutted cat didn't allow for a change in the reading, check engine light on. when you created a leak, there was a difference in the reading no check engine light. Maybe loooong stretch? __________________ LoverTechnologies "Half Broken Things!"

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05-19-2013, 05:11 PM	#3
Silvia716 Zilvia Junkie Join Date: Aug 2010 Location: buffalo ny Posts: 302 Trader Rating: (1) Feedback Score: 1 reviews	Cuz of your 02 sensor and you probly could use a new cat too

05-19-2013, 05:20 PM	#4
Lilredsx Join Date: Jun 2012 Location: FL Posts: 16 Trader Rating: (0) Feedback Score: 0 reviews	I was trying to find a picture of what the inside of a cat is supposed to look like. There is nothing inside this one at all, it goes straight through. I found this link and I did not have the shield that he has under his cat on mine, so maybe someone before me gutted the cat. http://zilvia.net/f/s-chassis/427317...t-install.html i guess I'll get the bolt and studs fixed and see what it does then.