posted by
someone claiming to be Don in Denver
on
Thu Mar 2 14:53 CST 2006 [ RELATED]
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Replaced knock sensors 3 yrs. ago & everything was fine until a few weeks ago
when the check engine light returned. According to info on this forum, the only
way to permanently get rid of these false codes is to replace the ECU. If the problem is the ECU, wouldn't I still have the same problem with another one? Or
should I get an ECU from a different year-such as a '95?
Thanks for any suggestions.
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Well took the car to the dealer and it turns out that after the knock sensors were checked, we thought the ECU was to blame for the knock sensor code. Dealer removed the ECU, cleaned the terminals, and replaced. NO CODES. Turns out in my case, the ECU's terminals had started to corrode and that was causing the faulty knock sensor code.... Driving happily with no check engine light on again.
Hope this helps others..
Over a million Volvo miles and still smiling....
Oliver
64 122S
66 1800S
86 245DL
96 850GLT
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posted by
someone claiming to be Steve
on
Sun Mar 5 11:30 CST 2006 [ RELATED]
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I too replace my knock sensors (did it myself) about 4 years ago. About 5 months ago the check engine light came on. After clearing the code it came back and it was the knock sensor. Since it ran fine and I didn't have time to mess with it, I left it alone (hoping the light might burn out). Well, about a month ago the light went off (didn't burn out) and has stayed off. Can't explain it.
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posted by
someone claiming to be MadeInAmerica
on
Sat Mar 11 04:12 CST 2006 [ RELATED]
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Well isnt the knock sensor to say the engine is knocking? I have had it make the check engine go off.....maybe 3 times in 5 years......I put in high octane gas it doesnt come back on........clear codes and always use the high octane gas...I also get better gas mileage with the high octane gas to compensate for its price
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Steve,
Can you please tell me where the sensors are located and how difficult they were to replace.....
Over a million Volvo miles and still smiling.
Oliver
64 122S
66 1800S
86 240DL
96 850GLT
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They are under the intake manifold to the right and slightly above the oil separator/oil trap, and there are two of them attached to the engine block...you have to take the intake manifold off to get to them. If you're going this far, get your pcv system cleaned and replace the oil trap while you're in there...cheap insurance that will help prolong your rear engine seal from springing a leak.
--
1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.
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Thank you. Sounds like a fun weekend ahead.....
Over a million Volvo miles and still smiling....
Oliver
64 122S
66 1800S
86 245DL
96 850GLT
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Don,
Please clarify the issue here.
You state that you had problems three years ago and that the problems were resolved.
Now, you say, the check engine light is on.
The check engine light can come on for about 1.2 million reasons.
Why do you think it is the same problem as before? Did you check the code (your posting does not state that you did)?
So, before we start talking about replacing expensive ECUs, let's figure out what the problem is.
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posted by
someone claiming to be Don in Denver
on
Fri Mar 3 12:48 CST 2006 [ RELATED]
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Yes, the codes were checked & they indicate knock sensor problems. I deleted
the codes but they returned. My independent Volvo mechanic says it's notunusual
for these codes to return and advised me to forget it as it's basically a non-
problem other than having the check engine light on all the time(the car runs
great, I have all the required maintenance done). I may want to sell the car
some time & figure that a check engine light would detract from the sale.
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That's all true, not to mention not being able to pass state inspection with the CEL on as well as with it being on, you might be masking something more serious that is going wrong with your car. Just a bit of info about the ECU (not sure why you assume that you should change yours out): You CANNOT use an ECU from a different year. It has to be the same one that's in your car already or it won't work. A number of reasons for this which I won't go into right here or now.
Another thing...could have just gotten a batch of bad gas. Try buying higher octane gas and from a different place and see if your CEL for the knock sensor goes away.
--
1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.
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Don, Don't know if you have a code reader to verify/reset the code. How frequently is is occuring? Can you get at the connector easily? A lot of these connectors respond well to a bit of elctrical grease and a wiggle. They tend to oxidize over time. I'd try these items before buying an ECU myself.
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Have the same issue right now on my 96 850. Can't decide if I should let the dealer replace the sensor and "maybe" fix it or if I should just buy a used ECU and replace that myself....
A fellow brickboarder recommended the following:
"www.car-part.com. This is a great site for used parts. I was upgrading my ECU, and I needed an extra ECU - I found one of the wrecking yards. It was tested, and it has no problems at all. It cost $90. Look at the code on the ECU and make sure it matches with the one you are looking for. Looks like the lowest price for a used ECU is $65."
When you had the sensor replaced three years ago, did that fix the problem? Did you have a dealer do the work - if so what was the cost? If not how hard was the sensor to change?
Thanks in advance
Over a million Volvo miles and still smiling.
Oliver
64 122S
66 1800S
86 240DL
96 850GLT
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posted by
someone claiming to be Don in Denver
on
Sat Mar 4 03:56 CST 2006 [ RELATED]
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Oliver--I guess my real question is why replacing the ECU solves the problem.
Are ECUs different so that the replacement responds differently to the sensor
input? Would a 95 ECU work in a 94?
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Don,
From what I have been able to find out, the ECU has a code on it that must be the same as the replacement. I do not know if ECU's with the same code were used for multiple model years.
I know on my 96 model, the check engine light came on about three weeks after the timing belt and 130,000 maintenance was done by the local dealer. The only code is the Knock Sensor code, and the code returns as soon as it is cleared. Like your car, my car runs great, but that damn light is pretty frustrating.
Please let me know if you are able to find out anything else. Mine is going back to the dealer next week, and I will post the results of their finding.....
Over a million Volvo miles and still smiling.
Oliver
64 122S
66 1800S
86 240DL
96 850GLT
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I reached down and unplugged and repluged the rear knock senser wire 3-4 times and the cleared the code. It came back 60k miles later and I did the same thing still off. signed bloody knuckles. I don't want to take off the intake unless I have to. I believe you lose turbo boost with the knock senser mil light on.
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Rick,
Can you please describe where the sensors are located..... I would like to verify the connection of mine but have been unable to determine their location...
Over a million Volvo miles and still smiling.
Oliver
64 122S
66 1800S
86 240DL
96 850GLT
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posted by
someone claiming to be Don in Denver
on
Wed Mar 8 06:12 CST 2006 [ RELATED]
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I believe there are 2 sensors, located at opposite ends of the engine block,
underneath the manifold. I know when I had the sensors replaced 3 years ago, most
of the $300+ cost was the labor to remove and replace the manifold. The actual
cost of the part was about $98. I'm going to talk to my independent Volvo mechanic
again as he had an idea that there might be a little carbon build up on the pistons which could alter the detonation inside the cylinder and that decreasing
the turbo boost might get rid of the knock sensor codes. We'll see.
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Clean the pcv system hoses and oil trap and as well as checking all of your other vacuum hoses (especially elbows) as well as your intercooler hoses from the one coming off of the trottle body, all the say to the one that comes off the lower, driver's side of the intercooler and curves up and over to enter the turbo...and this will help your boost more than anything. You can order silicon hoses at a savings from stylin motors and it will also help with boost. Here is a link for them: http://www.stylinmotors.com/volvo.html
This in itself may help your knock sensor issue. Good luck!
--
1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.
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