| MixManMash |
Hey guys,
I ran an ECU diagnostic yesterday and I got a code 34 - detonation sensor (i.e. knock sensor).
So I clear the ECU, start the car and let her run for about a minute. She comes up code 55 - no problem :)
Then I start her up, take her for a drive. I get code 34 again. :(
The funny thing is that with code 34, I should be running in Safety boost. However, the stock boost guage (now, I know it is a POS) shows me about 500 mmHg = 9 psi. Isn't safety boost at 7 psi?
The other funny thing is that only after I drive the car, it returns with code 34. If I clear the ECU, then let her idle for a few minutes, it comes up clean. I tried this several times.
I am planning on taking my digital multimeter from work and ohming out the connections.
Very weird. Any suggestions (besides getting an after market boost guage)?
Thanks in advance.
Mahesh.:( |
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| Lococoin |
i dont know much about your car but id check the plugs to see if there is any signs of detonation at all.
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| vorpalz |
Code 34... not fun. You won't get a code while idling, as I believe the car has to be pulling in gear for the det. Sensor to be "active". You probably have a bad harness, pull the connector and clean with contact cleaner, or a small file to remove vertegris from the contacts. Connect it and drive around, pulling in 2nd or 3rd from ~ 2500 RPM. If that doesn't remove your code 34, you can buy a Nissan sensor and mount it on top of the engine, there is a write-up on www.twinturbo.net in the autoFAQ, I believe. I had code 34 before I had my engine rebuilt, and I soldered in a resistor in the ECU connector side of the harness, it fools the ECU into thinking the Det. Sensor is fine. Not what I would recommend as a permanent repair, you should really get the det. sensor and harness replaced. If you are going to pull the tranny for a clutch replacement, you may be able to replace the det. sensor in its stock location.
Good Luck!
Regards, |
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| Inzane |
quote:
Originally posted by Lococoin
i dont know much about your car but id check the plugs to see if there is any signs of detonation at all.
Having detonation, and pulling a code for a bad detonation sensor (the problem here), are two completely different issues.
MixManmash:
I haven't personally had any trouble with my detonation sensor (yet), but Rob's (VorpalZ) advice sounds good to me.
Try this link as well:
http://www.twinturbo.net/net/viewms...p;msg_id=786419
Good luck with your diagnosis.
Jason |
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| Lococoin |
ya i misread what he was asking. i thought the sensor was working but was going off, hence concerns about detonation. :)
Im unfamiliar with knock sensors as my b18a1 doesnt have one. So when your engine senses knock it cuts boost and retards timing? A code is only given when there is a problem just like any other code? |
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| Inzane |
quote:
Originally posted by MixManMash
The funny thing is that with code 34, I should be running in Safety boost. However, the stock boost guage (now, I know it is a POS) shows me about 500 mmHg = 9 psi. Isn't safety boost at 7 psi?
You're right, safety boost is normally ~ 7 psi (assuming you are not running a boost controller yet and have not changed your wastegate actuators, etc.). On a stock TT anyway.
If your detonation sensor detects detonation, it will put you in safety boost mode. But does code 34 (which doesn't necessarily mean the presence of detonation) automatically throw the ecu in safety boost mode... that I'm not 100% sure of. (Rob?) And it may depend on what's actually causing the code to appear. Bad sensor... bad connection... etc.
But yes, the stock boost gauge is crap and you can't rely on it for any bit of "accuracy" at all in terms of what your actual boost level is. |
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| MixManMash |
Thanks for your help guys. You guys are awesome :)
BTW, in my reading I did find somewhere that Code 34 does retard timing to low octane levels and does put the car into safety boost. I think it was either on twinturbo.net or 300zxclub.com
I am gonna try some more diagnostics tonight and hopefully figure out what's wrong and the solution.
I will post a response either way. |
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| MixManMash |
Hey Guys,
I ohmmed everything out and it seemed okay. except on the contact going to the det. sensor, I was getting erratic readings. So I cleaned it out with contact cleaner (thanks for the hint Rob) and started her up. She runs smoother. I drove nice and slow, warmed her up, took her up to about 3000 rpm and came back. Check the codes again and I am getting 55. Took her out for a hard run and ran the codes again.
ALL IS CLEAR - 55
:D
Thanks again guys. Appreciate your help and wisdom. |
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| MixManMash |
BTW,
the stock guage is crap is it is now closer to 700 mmHg = 14 psi. There is no way I am at 14 psi with stock everything except for the pop charger.
I guess I'll look into getting an aftermarket guage. Any hints on which one and where to get it are much appreciated. |
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| vorpalz |
Good Job! (you were lucky...) My Code 34 wouldn't disappear until I did the resistor trick. Safety Boost is pretty noticeable, the car is sluggish to accelerate (timing restriction) and boost is sharply restricted. Maybe you weren't in safety boost? Strange.
My understanding fo the Det. Sensor circuit is that Code 34 is thrown when the resistance from the sensor exceeds the parameters outlined in the ECU. It could be from corroded connectors causing a sensor malfunction. If you are getting safety boost from poor octane, the det. sensor is acting as it should, and you'll get no code, just poor performance until you switch the ignition off and on again.
As for boost gauges, everybody has their favorites, but I went with Autometer 2601 Boost/Vac guage and Autometer pillar pod. Got both from Mopac for ~ $ 80.00. Mechanical guage, easy to install, blends in well with the stock instrumentation.
Coming to next Thursday's meeting?
Regards, |
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| MixManMash |
I'll be there next Thursday.
Thanks. |
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| MixManMash |
Got code 34 again.
Measure the resistance from ground to the one lead on the harness going to the knock sensor and I am getting 20 megaohms instead of 1 megaohm....
Looks like I will be replacing the harness going to the sensor. I messed around with that harness a couple of times and it worked great for a couple of drives and then back to square one.
Question is: is it possible to replace this small harness while changing the clutch?
Thanks. |
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| ~30oZ~ |
quote:
Originally posted by vorpalz
Coming to next Thursday's meeting?
A meet next Thursday?:dunno: I didn't know of any...still need to come out and say Hi. |
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| vorpalz |
That meeting was Thursday Aug. 4th! Next club meet is Sept. 1 at the German Canadian Cultural Centre, 8310 - Roper Rd. C'mon out!
As for your question about the sensor harness, MixManMash, no less an authority on twinturbo.net Ash Powers says it can be reached with the tranny dropped. It's bolted to the block below the back of the plenum.
tt.net link
Sounds like something to do when the clutch is replaced.
Regards, |
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| MixManMash |
Okay. So I tried to get my hands on just the harness piece for the knock sensor. Apparently, it's not in the parts catalog according the the gentlemen at Mills Nissan (they are very close to where I work so I just zipped over there) and you have to buy the knock sensor which comes with the harness piece.
However, I did find it at courtesy parts.
http://www.courtesyparts.com/Mercha...;Category_Code=
Any other hints? If not, does anybody want parts from courtesy (trying to buy as much as I can to minimize the overall cost of shipping)? |
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