Code 34 Knock sensor issues - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Zach321 · 09-12-2013, 11:37 PM

I've got a freshly rebuilt dohc ka, s13.

I checked my ecu for codes a while back, and it threw 34 for the knock sensor.

I replaced the knock sensor, still threw the code. After that, I replaced the subharness that goes from the wiring harness to the knock sensor.

I ohmed the old sub harness and it had read 0 ohms, I ohmed the new one and it had 0.5 Mega ohms, I believe, or could be Kilo ohms.

Thinking I had fixed the problem, I reset the ecu and it threw 34 once more. I checked the sender wire and it was sending 5v to the sensor, as I read that it should be. So after replacing everything, its still throwing the code.

The CEL doesn't normally come on when I'm driving when the engine is cold, but it comes on when its warm and when I'm accelerating, under deceleration the light goes off. I'm completely stumped. When the CEL lights on, I can feel it miss a bit and it doesn't feel right. But when the lights off, it runs pretty smooth.

What could this be? I've read things like, bad neutral position switch, bad transmissions, mounts and leaky injectors. Far out things that wouldn't have anything to do with the knock sensor but I just don't even what to do now.

Should I bypass it?

Davidna2fi · 09-20-2013, 05:52 PM

Nope, nissan ECU needs the knock sensor signal so adjust timing depending on load so it reduces knock or elimates it. I would double check the ignition timing settings first, possible that the engine is really detonating a lot if its' too far advanced. Does it seems really sluggish before it gets into boost, or takes too long to spool? Could be signs of timing issue. Also slight bucking without boost also can indicate timing issue. But if you step into it and it goes like a bat out of hell, more than likely the timing is really advanced beyond what the factory ECU can compensate for. Search for timing check, it's not as simple as you think, Nissan has a trick so that the ECU will lock in the base timing so it can be seen, you can't just stick a light on and then it shows correctly. By all the things you've done, it's nothing to do with the knock sensor circuit since it happens when driving a certain way. If it was circuit or sensor issue it would happen regardless of driving cylce.

AS240 · 09-21-2013, 09:38 AM

^Agreed. From what you're saying, it seems like the knock sensor is actually doing it's job. It does sound like a timing problem to me. How long did your car sit? Are you still running on the fuel that sat in the tank while you rebuilt your motor? And is it 93 octane?

Zach321 · 09-21-2013, 09:46 AM

I'm not running boost, it's n/a. It's 20 degrees BTDC at idle like it should be, but when I giving throttle the timing seemed to advance very inconstant and didn't seem right when I let off throttle. I'm no master with timing or a timing light. I do have a noise in the head somewhere, could be timing chain guide. The upper guide that's on the head under the valve cover broke while I was driving one day, and was getting thrown around by the cams. Could that have possible damaged something and causing that noise?

My car sat for about 8 hours and I started it, let it idle until operating temperature, and it drove home flawlessly, and the CEL didn't come on once. But when I got to my house I turned it off and started it again, and the CEL came on. I looked at all my plugs and they seem to be fine, gapped to spec, etc. I use premium gas so I'm doubting that it's an actual detonation knock.

Maybe my ecu is tripping out? Still stumped. Sometimes when I try to check the codes my ecu won't throw any. Not even a 55 (all systems go) or 34, what it normally throws. Almost everything is new. Maybe I have a short or bad ground somewhere?

Thanks for the reply!

Zach321 · 09-21-2013, 09:49 AM

Quote:

Originally Posted by AS240

^Agreed. From what you're saying, it seems like the knock sensor is actually doing it's job. It does sound like a timing problem to me. How long did your car sit? Are you still running on the fuel that sat in the tank while you rebuilt your motor? And is it 93 octane?

I run 92 octane and my tank looks great. I put a walbro in yesterday and my tank looked way better than I expected. I've got 12k on the motor and never used that shitty fuel that was in there.

Could something other than detonation cause my knock sensor to send signals?

Zach321 · 09-21-2013, 09:50 AM

Quote:

Originally Posted by Davidna2fi

Nope, nissan ECU needs the knock sensor signal so adjust timing depending on load so it reduces knock or elimates it. I would double check the ignition timing settings first, possible that the engine is really detonating a lot if its' too far advanced. Does it seems really sluggish before it gets into boost, or takes too long to spool? Could be signs of timing issue. Also slight bucking without boost also can indicate timing issue. But if you step into it and it goes like a bat out of hell, more than likely the timing is really advanced beyond what the factory ECU can compensate for. Search for timing check, it's not as simple as you think, Nissan has a trick so that the ECU will lock in the base timing so it can be seen, you can't just stick a light on and then it shows correctly. By all the things you've done, it's nothing to do with the knock sensor circuit since it happens when driving a certain way. If it was circuit or sensor issue it would happen regardless of driving cylce.

I'm not running boost, it's n/a. It's 20 degrees BTDC at idle like it should be, but when I giving throttle the timing seemed to advance very inconstant and didn't seem right when I let off throttle. I'm no master with timing or a timing light. I do have a noise in the head somewhere, could be timing chain guide. The upper guide that's on the head under the valve cover broke while I was driving one day, and was getting thrown around by the cams. Could that have possible damaged something and causing that noise?

My car sat for about 8 hours and I started it, let it idle until operating temperature, and it drove home flawlessly, and the CEL didn't come on once. But when I got to my house I turned it off and started it again, and the CEL came on. I looked at all my plugs and they seem to be fine, gapped to spec, etc. I use premium gas so I'm doubting that it's an actual detonation knock.

Maybe my ecu is tripping out? Still stumped. Sometimes when I try to check the codes my ecu won't throw any. Not even a 55 (all systems go) or 34, what it normally throws. Almost everything is new. Maybe I have a short or bad ground somewhere?

Thanks for the reply

09-12-2013, 11:37 PM	#1
Zach321 Join Date: Sep 2013 Location: Tennessee Age: 32 Posts: 4 Trader Rating: (0) Feedback Score: 0 reviews	Code 34 Knock sensor issues I've got a freshly rebuilt dohc ka, s13. I checked my ecu for codes a while back, and it threw 34 for the knock sensor. I replaced the knock sensor, still threw the code. After that, I replaced the subharness that goes from the wiring harness to the knock sensor. I ohmed the old sub harness and it had read 0 ohms, I ohmed the new one and it had 0.5 Mega ohms, I believe, or could be Kilo ohms. Thinking I had fixed the problem, I reset the ecu and it threw 34 once more. I checked the sender wire and it was sending 5v to the sensor, as I read that it should be. So after replacing everything, its still throwing the code. The CEL doesn't normally come on when I'm driving when the engine is cold, but it comes on when its warm and when I'm accelerating, under deceleration the light goes off. I'm completely stumped. When the CEL lights on, I can feel it miss a bit and it doesn't feel right. But when the lights off, it runs pretty smooth. What could this be? I've read things like, bad neutral position switch, bad transmissions, mounts and leaky injectors. Far out things that wouldn't have anything to do with the knock sensor but I just don't even what to do now. Should I bypass it?

09-21-2013, 09:38 AM	#3
AS240 Zilvia Addict Join Date: Jul 2007 Location: Austin, Tx Age: 35 Posts: 683 Trader Rating: (18) Feedback Score: 18 reviews	^Agreed. From what you're saying, it seems like the knock sensor is actually doing it's job. It does sound like a timing problem to me. How long did your car sit? Are you still running on the fuel that sat in the tank while you rebuilt your motor? And is it 93 octane? __________________ '92 HB HX35 rb25 - sold '89 Coupe GTX35 VVT-I 2JZ - yeah buddy

09-20-2013, 05:52 PM	#2
Davidna2fi Zilvia Junkie Join Date: May 2008 Location: Houston, TX Posts: 513 Trader Rating: (18) Feedback Score: 18 reviews	Nope, nissan ECU needs the knock sensor signal so adjust timing depending on load so it reduces knock or elimates it. I would double check the ignition timing settings first, possible that the engine is really detonating a lot if its' too far advanced. Does it seems really sluggish before it gets into boost, or takes too long to spool? Could be signs of timing issue. Also slight bucking without boost also can indicate timing issue. But if you step into it and it goes like a bat out of hell, more than likely the timing is really advanced beyond what the factory ECU can compensate for. Search for timing check, it's not as simple as you think, Nissan has a trick so that the ECU will lock in the base timing so it can be seen, you can't just stick a light on and then it shows correctly. By all the things you've done, it's nothing to do with the knock sensor circuit since it happens when driving a certain way. If it was circuit or sensor issue it would happen regardless of driving cylce.

09-21-2013, 09:46 AM	#4
Zach321 Join Date: Sep 2013 Location: Tennessee Age: 32 Posts: 4 Trader Rating: (0) Feedback Score: 0 reviews	I'm not running boost, it's n/a. It's 20 degrees BTDC at idle like it should be, but when I giving throttle the timing seemed to advance very inconstant and didn't seem right when I let off throttle. I'm no master with timing or a timing light. I do have a noise in the head somewhere, could be timing chain guide. The upper guide that's on the head under the valve cover broke while I was driving one day, and was getting thrown around by the cams. Could that have possible damaged something and causing that noise? My car sat for about 8 hours and I started it, let it idle until operating temperature, and it drove home flawlessly, and the CEL didn't come on once. But when I got to my house I turned it off and started it again, and the CEL came on. I looked at all my plugs and they seem to be fine, gapped to spec, etc. I use premium gas so I'm doubting that it's an actual detonation knock. Maybe my ecu is tripping out? Still stumped. Sometimes when I try to check the codes my ecu won't throw any. Not even a 55 (all systems go) or 34, what it normally throws. Almost everything is new. Maybe I have a short or bad ground somewhere? Thanks for the reply!