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Failed Emissions With A Vengance

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Old 07-13-2007, 05:51 PM
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I can't figure this out, I ran the codes on the ECU again. I did it because for the past 2 days my CEL has been coming on. It will be off most of the time, but for periods (10 minutes to a half hour) it will come on, sometimes flickering on and off for 2 or 3 second intervals at idle. So I ran the codes, and right off the bat I get code 34 (knock sensor circuit), which in the FSM isn't even supposed to trigger the CEL to come on. That's the only code I get. I turn the switch back and back to test and it then gives me 55 (no problems). I'm stumped here.
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Old 07-14-2007, 09:52 AM
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when you turn it back and forth, its not rechecking, thats how you clear codes. thats why it gives you a 55. you just cleared them.

knock sensors go bad and will cause your issue. its a PITA to change, you ive always just gotten another one and bolted it to the intake manifold on my personal cars. no problems then
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Old 07-14-2007, 12:33 PM
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Good luck if it is the knock sensor, I cant eve get to it with my big hands. Resetting codes you usually have to wait 30miles or until the ecu calibrates to TP.
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Old 07-14-2007, 10:05 PM
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Okay, but if there was more than one code stored it would have flashed it right after the knock sensor code, right? The FSM says that the knock sensor doesnt throw the CEL. How would the knock sensor make me fail emissions?

I just looked online and knock sensors are expensive as *****. DOH!

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Old 07-15-2007, 07:44 AM
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knock sensors DO throw CEL!! obviously, bc theres a damned CEL code for it!!

when knock sensors go bad, it puts the motor into a 'safe' mode and makes it run incorrectly.

as far as pricing, brand new anythings are expensive! you can buy a used SR MAF for 50 bux, but new theyre $4XX!!! just find a decent used one at a junkyard off a KA. most junkyards offer 5 finger discounts for parts this small!
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Old 07-15-2007, 10:56 AM
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lol I know, I would "borrow" it from the junkyard but didn't you say it was a pain in the *** to get out?

Heres the page from the FSM. See, it says it shouldn't throw the CEL.
Name:  240sxcodes.jpg
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Old 07-15-2007, 12:58 PM
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Originally Posted by Durdan
knock sensors DO throw CEL!! obviously, bc theres a damned CEL code for it!!

when knock sensors go bad, it puts the motor into a 'safe' mode and makes it run incorrectly.
The safe mode makes the engine run rich, this will increase HC's, and CO's.

When my speed sensor went out I was running rich on HC's. When my egr temp sensor went out I was runing rich on HC's and almost didn't pass CO's. The smog tech happen to be one of my friends so on the dyno we did a third gear pull to pass the sniffer under load.
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Old 07-15-2007, 10:18 PM
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Is there a way to eliminate the knock sensor, like cutting it off and tying the wires together, that will make the car get out of safe mode? Or do I absolutely have to get another knock sensor? My registration is due soon and I've been working a buttload.
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Old 07-15-2007, 10:23 PM
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I have a knock sensor sitting right here ill sell you for 30 shipped
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Old 07-15-2007, 10:37 PM
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I may have to take you up on that. Lemme mull it over.
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Old 07-15-2007, 10:43 PM
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Werd it's not going anywhere
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Old 07-16-2007, 01:35 PM
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Ry Ifeel you on this crap... I have to smog my S14 like... soon. My reg is due next month and I might have to go in for jury duty tomorrow... This is one PITA issue I have to face every time.

Hope everything is getting better for you buddy.
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Old 07-18-2007, 10:13 PM
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loserkid, I will buy that knock sensor from you. I PMed you.
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