Diagnosing DTC 44 (Knock sensor circuit)

[lonewolf41]

I have DTC 44 on my 5.0 OSi-E (serial 4012110198). I am going through Volvo's manual on troubleshooting and on step 5 it says to disconnect J1 and check J1-17 (knock sensor circuit) to ground. Value should be "93-107k ohms. My first question: is that 93 ohms to 107,000 ohms? That seems ridiculous, but OK, it may be that. I think it is supposed to be 93,000 ohms to 107,000 ohms.

My value was 3,870 ohms. So if the fist, I am OK. If the second, I am out of spec. I also disconnected the connector at the knock sensor and checked the sensor terminal to ground and got the exact same value.

I think I have a bad sensor, but am not 100% sure based on the vague information in Volvo's manual.

Secondly, if the sensor is bad, is there a GM sensor that I can go to the local auto parts store and pick up? It looks like a typical GM sensor that I have seen on numerous GM engines through the years.

Thanks!!

 

[alldodge]

The dreaded code 44 with MEFI. This code on a Merc is the ECM is unable to test the sensor on first throttle up. So it says sensor is not detected. I'm very familiar with this code with my new engine build and I disabled the code. It can be caused by using 93 octane because the higher octane fuel will not knock as easy as 87 to 90.

I have 2 manuals but unable to find the place your talking about in them

Value should be "93-107k ohms

This would be 93,000 to 107,000

 

[lonewolf41]

I am running 89 octane. For the Volvo, it seems to indicate that it can't see the knock sensor. It doesn't appear right away and only seems to set after I try and go above 3000 RPM. That is also where my engine stalls out. It makes good continuous power up until 3000 RPM and then just lugs down. I have a hard time getting on plane in fact. I can run the motor in the driveway and it doesn't show up...only when I put it in the water does it show up. From what I have read, and looking at the spark advance data, it quits advancing when it hits 3000. I assume that is because the knock sensor is bad and it doesn't want to advance it beyond that for fear of damaging the engine...or at least not knowing if it should or not so it defaults to some maximum value.

Thanks for the response.

 

[alldodge]

What your describing is how the ECM handles being unable to see (test) the knock sensor. My motor is 530HP and this is why I need at least 89 octane, but even this motor did the same thing when it could not see the sensor. If your stock then you only need 87

It can also be a bad sensor and just look up a GM 5.0 sensor for your year motor, they are standard. I picked up a new one from an online source. If you get a new one, install with the correct torque, to much or little changes the way it can sense

I'm showing J1-30 for the single KS, and my other manual has 2 KS then port is J1-27 and starboard is J1-29. Again unsure if this is for your motor. If correct you could check connections

 

[lonewolf41]

Well the plot thickens. Oreiley auto parts was able to cross the volvo part number (3850357) to one they had in stock. I bought it and before installing, I checked the resistance just for the heck of it. Low and behold, it has the exact same value as the one in the boat now. So now I don't know what to do. I think this new sensor will give the the exact same issue. I am attaching the pages from the manual that I am following. I am wondering if the people that rebuilt the motor used the same sensor (maybe from Oreileys) and they have the wrong one in their system. I really don't know where to go from here except order a Volvo part and see what it does.

Since I am getting the same value at the ECM terminal as I am at the knock sensor, I don't believe there is a problem with the wire. I also wonder if the manual is wrong. Maybe there was a misprint. I guess my next step is to call a Volvo shop and see what they say.

Any other ideas???

 

[alldodge]

We might be on to something, I'm looking a Merc service manual for code 44 and comparing to yours. Merc shows to measure the resistance the same way for BBC and SBC motors but different values.

BBC 3500 to 4700 ohms
SBC 3000 to 5000 ohms

So I'm thinking that your measurement should be between similar values which it is. My manual has 4 pages of changes to the manual where it points out incorrect information was omited or incorrectly entered. Since where talking about a wire and not a sensor then I think your wiring is good.

Measuring a knock sensor is useless because it has a crystal inside it set to vibrate with a given harmonic stimulus. If your sure your its not because of 89 octane. The MEFI 3 only checked on first throttle up, but does appear the MEFI 4 looks for a reading full time. ECM's work in milliseconds, so we would never know what its doing. Mercs got rid of code 44 with there MEFI 3 to 4 conversions for this very reason

 

[lonewolf41]

Just for grins and giggles, I hooked up my VOM to the old sensor and tapped on it with some pliers and was able to generate a small voltage. So it appears that the sensor is doing what it is supposed to do when it hears a "knock". I am at a loss. I rarely get stumped, but this one has me so far.

 

[alldodge]

Same here, do see how your getting a code 44 if the ECM is seeing something, but maybe its internal to the ECM. I have MEFI burn software and was able to uncheck (unflag) so it no longer will have a failure. Suggest calling Bob at OBD diagnostics to see if he has any comments on a solution.

Maybe muc might have an idea also

 

[Lubak572]

I have found errors in my Volvo Service manual

 

[Lou C]

Is there teflon tape on the threads....does this sensor have to ground on the engine...can it be that if there is Teflon tape or gasket sealer it prevents the sensor from getting a good ground?

I replaced a few of these knock sensors on my wife's old '98 Subaru, they had to be tightened to a certain torque I recall...

 

[lonewolf41]

Some excellent thoughts. I did not rebuild this motor and the folks that did SUUUUUUCK. I caught 3 or 4 things that were wrong before installing the motor. Maybe I missed one.

I will check on the tape. The old sensor was tight and I know there is a specific torque on it. The new sensor had thread sealant already on it so I assume that is OK. Will check in with Bob and see what he says. I think I will also go ahead and install the new sensor and see if it behaves differently and also just unplug it and see if I get the same error as that should mimic what is happening.

Thanks again for the feedback.

 

[lonewolf41]

Quick queestion AllDodge, is this the correct website for Bob?

Thanks.

 

[alldodge]

Quick queestion AllDodge, is this the correct website for Bob?

Thanks.

Yep, that's the pace

Sorry took so long, been cutting 13 acres and then just got off the boat from a float and cool down, I'm tired but at least refreshed now

 

[lonewolf41]

Thanks for the help. I think I have been chasing a ghost. I looked at the code again and it said 44-2 which I think is for the second knock sensor...which I don't have. Part of what I have been trying to do is verify what (if any) codes I have. The software I have been using was written for a Mercruiser, but I figured it would work for a Volvo as long as the ECM was the same. I tried...unsuccessfully...to read and codes via the DLC so I am going to create a new posting to try and figure out what I am doing wrong and why I can't read anything from the DLC.

Thanks again.

 

[alldodge]

My scanner is a Techmate and reads Merc, VP, Indmar, Marine Power

 

[lonewolf41]

My scanner is a Techmate and reads Merc, VP, Indmar, Marine Power

I have a Techmate as well, but of course, mine has old software on it and can't read anything past MEFI3 so it does not have the software version I need to read my ECM. $150 to upgrade. I think I would rather put that money towards something like MEFISCAN that allows me to view more info at a time. I have that now with some software that a member of another forum wrote and it is awesome. I just wanted to verify that the data I was getting (mainly the trouble codes) were correct for my ECM. I like being able to record and playback as well.

My theory is that any MEFI4 ECM would use and output the same data/info so that no matter which manufacturer you used, it would be the same. I may be wrong, but I assume the techmate does not distinguish between manufacturers...although it does ask you to select one, so maybe it is different and does distinguish between the different types/formats of data the ECM produces.

Thanks!