34 fault code if DET sensor detects knock ?!

Y

youngsyp

New Member
Hi,

I was having a play around with the car, and the Datascan software and noticed that the ecu was reporting a 34 fault code. It also stated that the car had been started 3 times since the code was logged.

Now, what I cant to know is, will the ecu throw up this code if it detects knock ? Or, will it only come up if, there's an issue with the knock sensor or it's circuit ?

I ask as, the car's been behaving just as normal, although, it has over boosted (quite a lot) as discussed in another thread.

I also cleared the code and went out for a play with my brother and his Evo 8 and it popped back up. Again, the car behaved as normal, with no loss of power or response etc... Again though, the car did slightly over boost (1.25 kg/mm).

Any thoughts would be great.

Paul
 
stumo

stumo

Active Member
if you're getting a code it means there's a fault with the circuit, which means either the wiring or the sensor itself, it doesn't mean it's detected knock.
 
Y

youngsyp

New Member
stumo said:
if you're getting a code it means there's a fault with the circuit, which means either the wiring or the sensor itself, it doesn't mean it's detected knock.
Click to expand...
Oh ****..... I thought that would be the response ! :doh:

Shouldn't a fault knock sensor or circuit, affect the way the engine behaves though ?!

Paul
 
stumo

stumo

Active Member
I believe that if there's a fault with the circuit (wiring or sensor) then the car won't run correctly as it goes into a sort of limp home mode, ie it doesn't give the engine full ign advance...that means less power.

If the fault dissappears then it will get full ign advance.

finding your intermittant fault will be a PITA. The loom goes round to the multiplugs on the drivers wing and also connects to the ECU loom.

Do all the usual earth checks etc

You can also check the wiring by measuring the resistance between the knock connector and the connector on the ecu plug (don't know which connector it is, i can find out on monday but i'm sure there's a connector diagram on here somewhere)

the knock sensor has a resistance of 600Ohms (from memory) on one of the connectors to earth (ie the back of the sensor as it earths through itself)
 
P

pulsarboby

Guest
as stu said above, it will put ecu into safe mode, but you wont notice a dramatic loss of power (just less althrough the range)
when engines cold there will be no difference atall as the ignition is automatically advanced anyway, but soon as the cold start comes off and it reaches running temp then you should notice a slight drop in power!
 
Braveheart

Braveheart

New Member
As above....
Also, ign timing is retarded by 6deg and the car will run rich and back fire alot more .
Under error code 34, my emissions were off the scale on CO2 tester.
I could reset ECU and clear the fault and the emissions would stablise.
New det sensor fixed the problem.
 
Y

youngsyp

New Member
Thanks Stu, Bob and Scott.

@stumo - I've got the service manuals on disc so, I should be able to find the wiring layout and plug/harness location.
I would expect it to go into limp/safe mode too but, there really is no change in performance. My brothers Evo 8 is running around 380 bhp and by his own admission, he could only keep up with me on a run and not gain any ground. We had a GPS timing device too and it matched his best 30-70 mph time down to the tenth of a second.
And I don't take the car over 3000 rpm or use any boost until the oil is at least 70 degrees C so, it's definitely warm.
There's also no back firing, overfuelling or loss in off boost performance that I'd associate with Scott's symptoms. Oh, and the base ignition timing was reported as 20 degrees BTDC, as expected on the Datascan.
With all that in mind, the fault code doesn't make sense.

I'll do a couple of datalogging runs later and see if anything obvious shows itself.

Cheers
Paul
 
Last edited:
Braveheart

Braveheart

New Member
I am not familiar with datascan
Maybe it's just throwing the fault up very breifly, recording it then clearing down and not there long enough for you to notice a drop in performace. This differs from my condition though. Fault code 34 would stay and the car would run like a dog until I reset the ECU.
It stayed clear for almost one week then latched on again... this happened 3 or 4 times before I decided to replace the sensor.
Think the det sensor wire comes out on pin 27 to ECU.

Sounds like the car is pulling fine and maybe you could live with this condition for now.
 
Fusion Ed

Fusion Ed

Active Member
Just thought I would say that some of the above is wrong.

If the ecu detects knock the ECU will change to the knock map, if the ecu still detects knock it will then report a fault. If the ECU has a problem with the knock sensor/wiring it will also show the knock fault and remain in the knock map. It will never enter limp with this condition.

It doesn't retard the ignition by 6 deg. It jumps to an entirely separate knock map, (and knock fuel map), this is the difference between the ign map and the knock ign map (ign map - knock ign=)

11 1 1 1 -1 0 -1 -3 -5 -1 -2 -3 -4 -3 -4 -6
11 1 1 1 -1 0 -1 -2 -5 0 -1 -2 1 -5 -5 -7
11 1 1 1 -1 1 0 -3 -5 3 2 0 -1 -3 -4 -5
11 1 1 1 -1 0 0 -3 -5 3 1 2 2 1 0 -2
11 1 1 1 0 1 -1 -3 -5 3 1 -2 3 0 -1 -3
11 1 1 1 0 1 0 0 -2 0 -1 -3 0 -2 -3 -5
11 1 1 1 -1 -1 -4 0 -5 -1 0 -4 1 -4 -5 -7
10 0 0 -2 -2 -3 -3 -4 -1 -3 -3 -7 -6 -1 -2 -4
10 0 0 -1 -3 -5 -5 -3 -1 -3 -3 -5 -6 -7 -8 -9
8 -2 -4 -3 -3 -4 -2 -4 1 -3 -5 -5 -7 -8 -9 -11
6 -4 -3 -2 -1 -4 -1 0 -3 -8 -7 -7 -8 -9 -10 -9
0 0 0 1 -3 -7 -7 -3 -10 -10 -11 -9 -10 -9 -10 -9
-5 -5 -5 -4 -4 -5 -3 -4 -12 -8 -9 -11 -12 -11 -11 -10
-5 -5 -5 -5 -8 -1 -2 -2 -8 -10 -9 -10 -11 -10 -9 -8
-10 -10 -10 -9 -2 0 -8 -11 -12 -9 -8 -9 -7 -8 -7 -7
10 10 8 8 8 7 -4 -7 -12 -7 -8 -7 -7 -5 -7 -5

Fuel when in the knock map is also altered, this is approximate AFR points different positive values would be richer and negative leaner.

-0.09 0.09 -0.09 -0.16 0.00 0.20 0.07 0.67 0.65 0.57 0.66 0.43 0.70 0.88 0.88 0.88
0.11 0.30 0.09 -0.10 0.43 0.23 0.66 0.49 0.46 0.50 0.82 0.67 0.59 0.76 0.76 0.76
0.31 0.50 0.60 0.84 0.69 0.41 0.31 0.43 0.28 0.59 0.68 0.58 0.45 0.65 0.48 0.48
0.52 0.52 0.52 0.79 0.74 0.27 0.26 0.55 0.31 0.15 0.45 0.37 0.35 0.45 0.34 0.34
-0.46 -0.46 -0.46 -0.58 0.00 0.10 0.84 0.90 0.43 0.62 0.64 0.52 0.48 0.63 0.34 0.34
-0.58 -0.58 -0.69 -0.46 -0.46 0.00 0.11 0.42 0.69 0.35 0.15 0.06 0.19 0.41 0.17 0.17
-0.58 -0.58 -0.58 -0.69 -0.23 -0.11 -0.11 0.00 0.00 0.50 -0.09 0.15 0.71 0.37 0.00 0.00
-0.95 -0.95 -0.83 -0.58 -0.34 0.00 0.00 0.00 0.21 1.03 0.17 -0.23 0.59 0.19 -0.12 -0.12
-0.46 -0.46 -0.35 -0.58 -0.23 0.11 0.11 0.11 0.21 0.21 0.64 -0.40 0.56 0.00 0.00 0.00
-0.58 -0.58 -0.35 -0.35 -0.34 -0.11 0.00 0.34 0.55 0.55 0.48 -0.25 0.22 -0.07 -0.07 -0.07
-0.46 -0.34 -0.34 -0.34 -0.35 0.00 0.11 0.23 0.23 0.34 -0.10 0.18 0.08 0.32 0.48 0.32
0.12 0.00 -0.11 -0.12 -0.12 0.00 0.00 0.11 0.11 0.23 0.09 -0.09 0.09 0.26 0.17 0.17
0.11 0.22 0.11 -0.22 -0.11 0.00 0.11 0.11 0.11 -0.41 -0.21 0.00 0.19 0.19 0.37 0.37
0.32 0.43 0.32 0.11 0.00 0.00 0.11 0.11 0.11 -0.21 -0.10 0.11 0.30 0.29 0.47 0.47
0.21 0.21 0.11 0.21 0.10 0.11 0.32 0.63 0.43 0.20 -0.21 -0.10 0.09 0.29 0.47 0.47
-0.55 -0.21 -0.10 -0.10 -0.21 -0.21 0.00 0.31 -0.20 0.00 0.00 0.11 0.09 0.29 0.47 0.47

If it were me I would clear the error codes, and see if it came back without over-boosting.
 
Fusion Ed

Fusion Ed

Active Member
Its possible to remove the knock sensor issue. Since they work over such a small range of engine region. I.e. full load BELOW about 4000 rpm (above this knock feedback is off) if you re-program the ECU with both knock and fuel maps the same it doesn't matter if the knock sensor error is there or not. Ok so its obviously nicer to have it all clear but in some cases you wouldn't want the knock sensor to play up if for example you were out in a race etc...
 
Y

youngsyp

New Member
Thanks Ed.

I'll check it again and if it's there, clear it down and change to a lower boost setting.
If it's still not reappeared in a week or so, I'll go back to the hi boost setting but, adjust it to reduce the spiking.

Paul
 
antgtir

antgtir

New Member
I had the Knock Sensor issue but mine by the sounds of it was more developed than yours Paul. My R was driving rough and felt like it held back so i ended up changing the sensor altogether. I re checked the ECU for the 34 fault code and all was gone, its not re appeared since.

The Knock Sensor issue was on top of my other hesitation / holding back issue (it never rains but pours lol).

When i removed my Knock Sensor i saw that there was a nasty crack around the sensor where the plastic sheath had split so it was probably the original and on its last legs.

If you need a sensor there is a guy that sells them, he has a 300ZX and advertises mainly for them. He is located on Ebay and lives just over the water from me. The part number is exactly the same as the GTiR sensor and as no one else bidded on this item at the time i had bid i managed to get the sensor (brand new, oe) for £50 bargain! you never know he may have another bargain waiting to be snapped up.

Hope you sort the issue mate.

Ant.
 
Y

youngsyp

New Member
Thanks Ant.

I reset the ecu yesterday and took it out for a couple of data logging runs with the max boost level set at 1.05Kg/mm.
Touch wood, after a WOT run, the fault code didn't return. I'll keep an eye on it this week and if it stays clear, I'll turn the boost up to the 1.15Kg/mm maximum but, re-set the AVCR so, it doesn't over boost.
That should be fairly easy as, it seems to 'go mad' just as the turbo reaches peak spool at between 3k and 3.5k rpm !

Paul
 
Y

youngsyp

New Member
Bastard 34 code's popped back up again, despite me just pootling around last week.

Datascan stated that it had been present for the last 6 starts of the engine. I reset the ecu on Monday and started the car much more than 6 times since this evening so, the fault is intermittent at best and again, doesn't impact performance.

So, what's the easiest way to get the plenum off, in situ so, I can check the sensor and it's wiring ?

Cheers

Paul
 
Y

youngsyp

New Member
Braveheart said:
It's a bitch to get at Paul.
There is a how to guide:
http://www.gtiroc.com/forums/showthread.php?t=31171
Click to expand...
Thanks for that Scott but, I was going to try a different approach... I.e. from the top down.

What I want to do is just remove the top half of the plenum, not the entire thing. I've seen it done with the engine in situ before but, they didn't let on how they got to the couple of pesky cap screws that sit just in front of the fire wall.

I'm guessing a cut down allen wrench and spanner ?!

Paul
 
Braveheart

Braveheart

New Member
OK Paul... best of luck.
I'd put money on it being the sensor although I still can't understand why the car runs fine. Keep us posted!
 
Y

youngsyp

New Member
Braveheart said:
OK Paul... best of luck.
I'd put money on it being the sensor although I still can't understand why the car runs fine. Keep us posted!
Click to expand...
Thanks Scott.

From further reading, it would seem that I'm going to have some fun removing the 'Y' bracket. :doh: :lol:

I've just seen a thread that mentioned a partially blocked fuel filter as a possible cause of the fault code. Mine needs changing so, I'll check that out first.

Paul
 
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