Mornin chaps!

This possibly follows on from my momentary power loss incident ( http://briskoda.net/forums/topic/162116-momentary-power-loss/page__p__1988846__fromsearch__1entry1988846 ).

After that happened, I drove all of about 10 miles, then parked the car up for the week. At that point I found no error codes, so went with the assumption that the momentary power cut was due to a shortage of fuel. So a week later I hop in the car, brim the empty tank with about 50 litres of Tesco 99, and set off on a 230 miles drive. After the drive I pick up the following code:

16712

(-163, KWP1281, 01/01)

Knock Sensor 1 (G61): Signal too High : P0328

That surprised me, as the car drove perfectly. After having a think, I decided it could have been caused by a sudden fuel shortage (lean mixture). Does anyone agree with this guess?! My dad then reminded me of the fact that it's not good to suddenly cut fuel on a turbocharged car, as you run the risk of putting a hole in a piston! Thanks for the support dad!! Anyway, I cleared the code and got back in the car.

I have since done 350 miles, and the code has not come back.

Now my question is why didn't that code pop up after the power loss incident, when I scanned it right after it happened, if they are related? And what does signal too high relate to on a knock sensor? Does it mean pre-ignition, knock, or no ignition etc?

The fuel in tank at the time of incident was probably about 4 weeks old (had a quiet month!), and the tank never really gets run dry, so I'm thinking the dregs of fuel in the bottom were of poor quality, and I experienced power loss due to a retarded ignition, caused by the knock sensor picking up pre-ignition or knock, which was caused by crappy/no fuel. Does that make any sense, or am I completely wrong?!

Sorry for rambling! Any comments appreciated, and thanks in advance

Edited 12 July, 201015 yr by Bodge

I think the issue needs a to appear a few times before it's picked by the ecu.

And I'm little dubious about the whole crap in the tank thing, dosen't the fuel filter cover this, fuel going off slightly maybe, but crap in the lines should'nt happen should it ??

I thought the "signal too high" faults usually indicated there was a fault with the sensor itself, rather than that there was knocking or pinking occuring? Thats certainly been the case on other sensors I've replaced (ABS sensor, coolant temp sensor)

I think the issue needs a to appear a few times before it's picked by the ecu.

And I'm little dubious about the whole crap in the tank thing, dosen't the fuel filter cover this, fuel going off slightly maybe, but crap in the lines should'nt happen should it ??

Yeah I thought that too about the fault needing to be picked up a few times. Confusing!

When I said crappy fuel I meant like low octane/poor quality fuel (like you say gone off fuel), rather than actually crap in the fuel. I agree the filter would stop any physical debris. I don't know enough about petrol to know how it might separate in a tank though. Just a guess!

I thought the "signal too high" faults usually indicated there was a fault with the sensor itself, rather than that there was knocking or pinking occuring? Thats certainly been the case on other sensors I've replaced (ABS sensor, coolant temp sensor)

Ahh that is something that I have ignored! An actual faulty sensor!

I just thought that it only happened once, and the sensor kicked up an error as it picked up a reading outside of it's set operating conditions. But I'm not even sure that it would do this.

If I get the error code back again, I will try changing the knock sensor. Don't suppose you know how much they are?! I'm guessing they are somewhere on the top edge of the block, or on the head somewhere.

Car is running perfectly so no rush luckily. I'll make sure I only use 98+RON fuel for now, just incase I do have a dippy knock sensor.

No idea how much they are but they're located on the front of the engine block itself, under the manifold, there's one for cylinders 1 & 2 and one for cylinders 3 & 4.

No idea how much they are but they're located on the front of the engine block itself, under the manifold, there's one for cylinders 1 & 2 and one for cylinders 3 & 4.

£45.57 retail from Skoda!

Thankfully I get a chunky discount as a regular customer! But it still turns out at around £36....

you need to run a log on the knock cf to see if its fecked but it really would run like a dog if it was

When you fit them, torqueing them down correctly is very important. I think that they contain a piezo electric layer which produces an electric signal when it is distorted by the engine vibrations, so it doesn't want to be distorted when you fit it.

Right I've had a good read up on this now.

They need to be torqued to 20Nm to work correctly (as Fordfan mentioned).

They have gold plated connectors on them, and on the loom pins.

Knock sensor #1 (G61) works for cylinders 1 and 2, and is at the left hand end of the block.

If a knock sensor fails, the ignition will be retarded on the two related cylinders (in this case 1 and 2) by 6 degrees. Causing a reduction in power output.

Symptoms can include stumble or hesitation on acceleration.

Googling "knock sensor G61" brings up a few, normally unanswered threads, on lots of Audi forums. This thread is now making its way up the list, so hopefully I clear this up!

Knock Sensor G61

There's another free Google bump for ya

Let us know if it's easy to access and change, in case anyone else has this problem in future

They are a pig to get to, a lot easier with the inlet manifold off.

OK so I changed knock sensor 1 yesterday. It's pretty easy to access, and easy to change. I'll get some photos of the job up later.

However, being a lazy twonk, I couldn't be bothered to drive to my mate to borrow his torque wrench, so just did it up by feel. A quick test drive down the motorway revealed that the same error code has popped up again, so I cleared it, and did another test drive today, with the same result. Dammit! Before it would take about 500miles for the code to appear, now it's like 5miles! So I've made it worse!

I'm going to re-torque it tonight to 20Nm, and see if that fixes it. If not then I've crushed the poor thing, and I'll have to shell out again for another sensor.

Part of me is open to the possibility that it is something else, but I don't know what. The plug was in perfect condition, and the wiring all looks fine externally. Absolutely no other fault codes. I need a wiring diagram really. I need to know if the wiring goes direct to the ECU, or if it passes through some sort of signal amplifier or something.

Is there any way of checking the sensor with a multimeter?

I'm annoyed with myself for just cranking it on there! Blame the hangover.....

Right, all sorted! I slackened it off for a while, then re-torqued to the correct 20Nm, and magically no more error code popping up on my test drive route as it has three times in the last two days. Also I was getting a flat spot at high revs under load. For example at 120mph in 5th it felt like it was hitting a wall in the power, and the power just ended. Now sorted, and the car feels noticably faster. So a note for future DIY'ers, torque the knock sensors to exactly 20Nm, or they won't work properly!

Part numbers:

Knock Sensor 1 (G61) is 030 905 377C @ £45.57+vat rrp

Retaining bolt is N01033520 @ £0.42+vat rrp

Note that the original sensor was made by Siemens and had a steel core, the new one was made by Bosch and had a copper core (both parts under identical part numbers).

Let the DIY begin!

This is where it's located (removed here). It's the non rusty hole to the right of the 'stat housing:

Once everything is disconnected, I find holding it all back with zipties works well:

Bosch vs. Siemens. I think the Siemens one failed due to corrosion. Looking at the patent for the Bosch design they are pretty sensitive things.

New sensor fitted and plugged in:

Here is the patent for the Bosch knock sensor: http://www.freepatentsonline.com/5398540.pdf

It explains how it works, and what all the internal components are. Pretty interesting.

The only problem I came across was myself not following the instructions! I think I was lucky to have not damaged the sensor, and managed to get away with it this time. Hopefully this thread helps lots of people googling this problem!

Case closed!

Did you use a universal joint and extension bar or was it easy to get a torque wrench straight onto it from that angle?

Edited 13 July, 201015 yr by chicken_eyebrow

Result !!!

Good write up / pics

Did you use a universal joint and extension bar or was it easy to get a torque wrench straight onto it from that angle?

When I first did it all, with the junk out of the way as shown in the photo, I could get straight at it with the 13mm socket on a straight extension, with a short breaker bar on the end (but you could use a slide bar or ratchet if you wanted to). Basically there was enough space to get straight onto it with an extension, rather than using a UJ. Which made it nice and easy.

Last night when I came back at it to slacken it off and torque it up correctly, I didn't have to remove anything apart from a quick connector on the alternator (removed in the first pic), just to avoid damaging it (I also don't run either engine cover). You can get onto the bolt by popping the 13mm socket onto a UJ, then popping that onto the extension and torque wrench/ratchet. That slides down the gap between the alternator/manifold/vacuum bracket nicely, and made the job super easy! So if you ever need to check the torque on knock sensor 1, it can be done in seconds. The same can't be said for the 2nd knock sensor! Looks like the 90degree breather pipe would need to be removed to gain access. Still, it's not a crazy hard job.

One thing I've discovered while working on this area of the car is gloves! For the first time ever I don't look like I've been punching a barbed wire fence!

Thanks Bodge, doesn't sound too hard then. I still have the UJ and other bits somewhere from when I changed my thermostat. Hopefully I won't ever need to change the knock sensor though

This is now up in the guides section

Thanks Bodge

This is now up in the guides section

Thanks Bodge

No probs buddy. Hopefully it will be of use to someone.

Sadly the bloody error code is back for me! The car drives perfectly, so I'm lost.

I'm going to overhaul the fuel rail (new FPR, injector seals, clips & manifold inserts), and change the spark plugs this week. So maybe that will sort it?! Expect a fuel rail refurb DIY soon.....

Any further thoughts are welcome. I'm hoping it's not a dodgy wire in the loom!

I've just bought two repair wires from our local VAG parts place to attempt to cure a recurring fault with a throttle body angle position sensor, and they only come out at around £2 each. You just clip the ends, solder them onto a long enough piece of wire to reach both connectors, unclip the existing wires from the plugs and tape them back, and patch the repair wire in. Hell of a lot cheaper than a full loom

I've just bought two repair wires from our local VAG parts place to attempt to cure a recurring fault with a throttle body angle position sensor, and they only come out at around £2 each. You just clip the ends, solder them onto a long enough piece of wire to reach both connectors, unclip the existing wires from the plugs and tape them back, and patch the repair wire in. Hell of a lot cheaper than a full loom

Don't suppose you have a pin diagram for the ECU so I can check the wires with a multimeter before?

This seems to be a fairly common issue across the Mk4, Leon and TT cars, but it sounds like I'm the first to get it on an Octy!

I might make my own temporary mini-loom up to replace the two wires. Any idea what spec the wire needs to be?

I don't but I may be able to blag one from the guy helping out with the fault. Failing that, I think the official service docs have one. The wires may well be different for each component as there are multiple part numbers in the catalogue for subtly different connectors - in my case we're dealing with signal wires so they don't need to handle a lot of power.