DTC Code PO331 - '95 850 T5 200K plus miles

[Linanas]

My OBD II sensor read,
"PO331 - Knock Sensor 2 CKT Range/Perf (Bank 2)"

What is the knock sensor 2? Is that something serious? And how do I go about reparing it?

I can't find any information on it for my 1995 850 T5. Not sure neither if it's because I have more than 200 K miles on my car. The reason why I say 200 K is because I just finally fixed my Odometer, thanks for THIS FORUM.

I found a part on FCP for for $129.
Link: http://www.fcpgroton.com/product-exec/p ... ory_id/116

Not sure is this is exactly what I need.

Any body have this same problem or knows how to fix it?
THANKS IN ADVANCE TO EVERYONE FOR THIER HELP!

[MadeInJapan]

Hi there...your car has 2 knock sensors... If you were to take your intake manifold loose you would see one to the left and another one just to the right of that, both sort of right of center, attached to your engine. When these sense that your air/gas mixture isn't right they will initiate a change in your mixture to compensate via your car's ECU (computer). This code is telling you that the sensor on the right (assuming 1 is left and 2 is right, also referred to as front and rear- your code is for the rear signal. The front is the timing belt side) is not able to compensate and the end result is that you're burning either too rich or too lean....not sure which (unless you have black smoke, then I would say rich). The good thing is this code only registers as "faulty" where there are other codes that come up as "permanent fault." So there is hope for the sensor, in my opinion.
You might even hear some knocking of the engine. This is not good because knocking could cause detonation. If you're using low quality gas (no name), or for instance regular gas in a turbo engine, this could happen if the sensor is weak. On turbo's the manual recommends premium gas, so if what I'm saying registers with you, I would try to fill up next time with premium gas and reset the code and see what happens. If that doesn't get it, you might be in for a new knock sensor. Wiring has been upgraded so you'll have to get the kit you posted a link of...unless you go to a pick-n-pull and get one off of another 850. Good luck and let us know how things go.

Oh, one other thing...if you decide to tackle this by yourself...notice the way the sensors are positioned- very important. One (I believe the left one) has the connector at 3:00 and the right one at 4:30 (positioned like a clock). The new sensors need to go back on EXACTLY in these locations.

[Linanas]

Thank you for MIJ, for you time and detailed explaination!
Very helpful.

I usually fill up with '89 gas. I mean you can't blame me... gas is so expensive. The first owner of this car had all records and timely required maintainance performed. He has been pumping with '89 gas, so I figured it would be okay to continue doing it. Still performs like a champ.
I also sometimes gun the turbo a lot.
I hope this combination hasn't been F*ing it up.

Nonetheless, I'll take your first suggestion and start fueling my car with '91 as it should deserve. Then we'll see what happens from there.
I already erased the code and I haven't heard any hard knocking.

Do you know if there are any guides to do it yourself? Do you suggest I bring it to a specialist rather than doing it myself?

I'll keep you posted. Thanks again.

[MadeInJapan]

Linanas,
If you can do some wrenching, you can do this job yourself (if it's necessary). The main thing that you'll have to deal with his taking the intake manifold off and it's just a bit quirky getting to the lower bolts. If it comes off that means that the fuel injectors also have to be pulled out, and you'll need an intake manifold gasket and possibly 0-rings for the injectors (highly recommended to replace them if you're already in there anyway). There are write-ups for the PCV replacement that will have pictures of what this will all take. Btw, if you get this far, you might as well change out your PCV system...you're already in there with the oil separator (AKA: oil trap, breather box) anyway and your car will love you for it. In the meantime, try the higher octane gas. My experience has been I get better mileage with the Volvo turbo's when I use better gas anyway. Also, being summer time, the lower octane gas often contains 10~15% ethanol which can also do a number on the knock sensors.

[Ozark Lee]

The P codes get a tad confusing on the '95 models since OBD-II wasn't a settled set of codes at that time.

The cross reference shows a P0331 to be a rear knock sensor rather than a front but I don't know how accurate it is. Try pulling (and clearing) the codes from port A-2 then buy a tank of premium fuel. If the code(s) come back on the A-2 port it will help narrow the problem down.

Once the code is set the ECU will go into partial limp mode which will limit the boost and limit the timing advance. It also forces the injectors to run rich to limit heat.

...Lee