Knock Sensor 2 (G66) is it the front or rear sensor?

**getslideways** · 09-13-2008 09:10 PM

I have been receiving the error for Knock Sensor 2 (G66) signal to low, so i want to re-torq it to see if that fixes the problem before buying a new sensor. So what i want to know is this:

Knock Sensor 2 (G66) - is this the knock sensor at the front of the block, or is it the one at the rear of the block? or to phrase it another way, is it the one with the green connector or the one with the blue?

I have heard some different things from different users. One user had the same problem and changed the front sensor with the green connector and that fixed it, while i read another post saying that Knock sensor 2 is referring to the rear sensor and some of the written manual information is incorrect.

Just hoping for some clarification. and i hope its the front because the rear looks like a pain! thanks

**southpaw10** · 09-14-2008 12:15 AM

its the one closest to the firewall (the blue one). I was in the process of changing mine today, but it turned out to be too much of a pita. Couldnt get a socket on it so I went with a crow wrench, but I couldnt keep it straight so I said f it. I'll save it for another day when I have time to take the intake manifold off.

**Nebone** · 09-14-2008 12:20 AM

I found the error in the Bentley manual on this. G66 is the sensor near the firewall and tough to get to. It has the blue connector.

**getslideways** · 09-14-2008 02:24 AM

Originally Posted by southpaw10

its the one closest to the firewall (the blue one). I was in the process of changing mine today, but it turned out to be too much of a pita. Couldnt get a socket on it so I went with a crow wrench, but I couldnt keep it straight so I said f it. I'll save it for another day when I have time to take the intake manifold off.

Well if you tackle this project again and come out victorious please post up any and all tips that aid in the process lol!

**getslideways** · 09-24-2008 01:49 PM

just an update, i confirmed that what everyone was saying is correct, i unplugged the blue connector and started the car then vagged it, then it said i had both (g61) and (g66), so yup the knock sensor with the blue connector is the one i am after. Just wanted to update.

**southpaw10** · 11-29-2008 05:09 PM

I've finally got around to replacing knock sensor 2. Without any distractions I think I could have been done much quicker than 3hrs. If I had to do it again, it would certantly be a 1-1.5hrs job. I started by taking the throttle body off as I was going to clean it anyways. Then I moved onto the fuel rail and all the hoses connected to the intake manifold. Unbolted the intake manifold and pulled it out. Even with it out I could barely get at the bolt for the blue knock sensor. So I decided to dismantle the pcv hose from the block. With this removed I had enough room to fit a 13mm crow wrench with a swivel attachment on the bolt. Kind of a tight space to work in but finally swapped it out with the new one.

Put everything back on and tourqued the intake manifold to 10nm as well as the throttle body. From what I remember the knock sensors are suppose to be 8nm, but I tightened it a smidgen more than hand tight. Cleared codes and did a throttle body adaptation. It's got a little more kick as the timing is allowed to advance now that the sensor is functioning. No "knock sensor 2 signal too low" code yet so I think the problem is solved. Didnt start taking photos till everything was off. Pics didnt turn out too great, a little dark. Make sure you have some clamps to replace the one time use ones.
Knock sensor 2 is the bolt right above the green rubber O ring in the pcv housing

A little better picture here

The section of the pcv system I took off

New Intake Manifold Gasket. The section of the pcv system I disconnected is installed in this pic. Be sure to clean the surface before putting the gasket on

Walk through for throttle body
http://forums.audiworld.com/a4/msgs/1135779.phtml

Trevor

**getslideways** · 11-29-2008 06:32 PM

you are the man! thank you very much, i now feel brave enough to tackle this myself! So you said you did notice an added punch when driving? was it a little or pretty obvious? i was wondering if this would change once i got mine fixed, since it has been pretty sluggish ever since i bought it with the bad sensor. Any other changes since the swap? mpg or anything? Thanks again so much! I was thinking of getting the new sensor from ECS do you have any better suggestions? Thanks a lot!!!

**southpaw10** · 11-29-2008 07:11 PM

Before I replaced this, whenever I cleared the code I could do 1-2 pulls before the code would come up and power would drop down a notch. So yes there is a noticable difference. I dont think mpg would change after this, but If I notice something I'll be sure to post. I got the sensor from purems.com along with throttle body gasket and intake manifold gasket.