More engine check light questions

Squeaky · Post by **Squeaky** » 18 Apr 2007, 23:53

My 1994 850 Turbo Wagon has been displaying its check light off and on ever since I bought the car two years ago (300,000 plus kilometres). Code readings vary, but they always include the knock sensor, and much less often the front co2 sensor. The knock sensor has been replaced twice at the dealer along with some sort of "uprade" kit.

Once in a while the light goes off by itself for a few days, but always returns. If I have the codes cleared, it will last up to a week before coming on again.

I've become so discouraged and pee'd about the ongoing situation that I've taken to ignoring it for at least the last 5,000 kms. All this time, it has continued to run and start flawlessly, it goes like stink, and gas consumption has been very good and very consistant.

My questions are 1) if there really is a problem, why does it run so well, 2) if there really is a problem, why would it self-correct from time to time, 2) is there any way to know if I am doing any harm by contuing to drive it with the light on, 3) should I be loooking or listening for any specific indicators that harm is being done, and 4) has anyone simply disconnected the bloody thing, and if so, what's the easiest way to do so?

Thanks folks,
Murray

Post by **srnkanator** » 19 Apr 2007, 08:39

I think you meant an bad front oxygen sensor. These do go bad with time. You can get them from www.fcpgroton.com and install yourself, it isn't that hard and there should be a info here on how to do it. But f you getting good mileage, I doubt it

If you are sick of seeing your CEL, the easiest way is to just neatly place a black piece of tape over the area, or take off you instrument panel and take out the bulb, but I don't know if that is what you would want to do. there are instructions for that here as well in the repair database.

Post by **MadeInJapan** » 19 Apr 2007, 16:23

Never cover up or take out the bulb for CEL....this light on could be an indication of something very very serious with your car....Instead, get your codes checked to help you diagnose what is really wrong.
About the knock sensor...it could be an indication of low octane gas. What type of gas and octane rating are you running? Turbo's should take high octane.

Now, covering up the service reminder light is another matter.

larryh · Post by **larryh** » 19 Apr 2007, 19:49

Squeaky wrote:My 1994 850 Turbo Wagon has been displaying its check light off and on ever since I bought the car two years ago (300,000 plus kilometres). Code readings vary, but they always include the knock sensor, and much less often the front co2 sensor. The knock sensor has been replaced twice at the dealer along with some sort of "uprade" kit.

Once in a while the light goes off by itself for a few days, but always returns. If I have the codes cleared, it will last up to a week before coming on again.

I've become so discouraged and pee'd about the ongoing situation that I've taken to ignoring it for at least the last 5,000 kms. All this time, it has continued to run and start flawlessly, it goes like stink, and gas consumption has been very good and very consistant.

My questions are 1) if there really is a problem, why does it run so well, 2) if there really is a problem, why would it self-correct from time to time, 2) is there any way to know if I am doing any harm by contuing to drive it with the light on, 3) should I be loooking or listening for any specific indicators that harm is being done, and 4) has anyone simply disconnected the bloody thing, and if so, what's the easiest way to do so?

Thanks folks,
Murray

sounds like you've been ignoring it for two years!

1. the problem is most likely just an emissions issue. that's what the obd/cel was developed for. so your car may run fine, most likely it's just spewing more smog than it should. but it could be causing harm to the vehicle too...

2. read up -google-the obdII system and you should easily find an explanation of how it works and why the codes can come and go. it's kind of interesting..

2. take it to a shop...sorry

3. again, take it to a shop

4. sure, mostly a-holes trying to sell a car with a pesky light..

Post by **srnkanator** » 20 Apr 2007, 07:38

just telling him what he could do not what he shoulddo

If he can figure out what's wrong . . . read your codes

post them

https://www.matthewsvolvosite.com/chat/p ... hp?t=10758

and we go from there . .

Squeaky · Post by **Squeaky** » 21 Apr 2007, 00:59

Thanks all.

I haven't been ignoring the problem until the last little while - I've had the code read and reset several dozen times and invested a chunk of money into having it diagnosed by the local dealer and two other shops.

Could someone clarify something for me - if the CEL light is on and the code refers to 02 sensor failure, does this mean that it is likely running too rich or too lean? I don't want to be polluting, but I'd rather be running a little rich until I get this figured out.

Please note that sometimes the code indicates knock sensor problems only, and as I said, those bits have already been replaced twice - which is why I'm suspicious that it's giving false readings or being overly sensitive. Someone told me that the system in the '94 T5 was prone to faulty ops. Btw, I have had the hose/lines checked six ways from center for any vacuum leaks and replaced the gas cap.

The car has always seemed to be running so well that I guess I'm hoping that someone is going to say, "oh yah, I had the same experience with mine and it turned out that there was really nothing wrong - all it needed was a new $5.00 veeblefetzer (life is happy here in lala land!).

Larry - I won't be trying to sell the car any time soon because I like it very much - not withstanding this particular annoyance. What I was asking was if anyone had become so desperate that they had disconnected the light to save their sanity - but I do promise I'll try not to be an A-hole when I do sell.

Squeaky

Post by **MadeInJapan** » 21 Apr 2007, 05:57

There are several 02 sensor specific codes. Two of them, indicate running rich or running lean (high, low), so the codes should tell you what's up with that. Since your car has such high miles, I would go ahead and change the front 02 sensor anyway, but a lot of times it's vacuum hoses that are leaking that cause the 02 code. Check these hoses, especially the elbow connectors around the turn of the manifold on each side of the engine. Of these two, usually the one that's a culprit is the one on the power steering pump (passenger) side.

larryh · Post by **larryh** » 21 Apr 2007, 08:32

Hey squeaky, i didn't think you were trying to sell. sorry if it came across that way.

too bad the shops weren't more help to you. i guess some just want to take the money read the code, and kick you to the curb....

good luck,
Larry

Post by **Ozark Lee** » 21 Apr 2007, 13:13

I've had the code read and reset several dozen times and invested a chunk of money into having it diagnosed by the local dealer and two other shops.

Why on earth are you paying a shop to read the codes? Since you have a '94 it takes no special tools to read and clear them and it is built into the car.

http://volvospeed.com/CheckEngine.php

Read the codes from A-2 and A-6 and post them. We can be more precise in our suggestions if we know exactly which codes it is throwing.

They are explained here.

https://www.matthewsvolvosite.com/chat/p ... hp?t=10758

...Lee

Squeaky · Post by **Squeaky** » 26 Apr 2007, 00:33

Thanks again all.

Hey Larry - no problem!

Squeaky