Code 44: cannot detect knock sensor

P

Primouza

New Member
Jul 27, 2017
6
Boat Info
Sea ray 270 Sundancer
Engines
Mercruiser 7,4 MPI
Hi,

I have a Sea ray 270 Sundancer with a Mercruiser 7,4 MPI (MEFI-3) modelyear: 2000

I just scanned my ECM and found this error code. I cleared the code and ran the boat and the alarm goes off again.

My engine alarm goes off between a few seconds and a few minutes of going on plane above 3000 RPM. This is a new problem that just came up this season. The engine runs well when the alarm is off. The alarm does not go off if I reduce RPM to idle, but will go away if I shut off and restart the engine. But it will come on again when i get back on plane.

I've changed both knock sensors and mounted new connections on the knock sensors.

I've also tested the wire from the ECU down to the connector with a multimeter and it beeps, so it seems to get connection all the way.

I've sprayed all the connections I can se with CRC 5-56 just to be sure nothing has rust on it.

Does any of you have had the same problem and how the h*ll did you fix it??
 
Quite possible your engine is knocking, but you can't hear it. Old fuel maybe ?
 
Did you use new OEM sensors?

The reason I ask is there is an issue with GM's newer 4.8, 5.3 and 6.0 v-8's where knock sensors go bad. The replacement sensors from aftermarket suppliers fit well and have the correct resistance reading, but for some reason don't last very long, and in one case I came across, didn't work at all. On these automotive engines, (4.8, 5.3 & 6.0) using AC Delco knock sensors is the way to go.

Another thing, did you clean the threads before screwing in the new sensors? You should run the proper thread tap into the hole to clean out and rust and debris before installing the new sensors.
 
Espos4 said:
Did you use new OEM sensors?

The reason I ask is there is an issue with GM's newer 4.8, 5.3 and 6.0 v-8's where knock sensors go bad. The replacement sensors from aftermarket suppliers fit well and have the correct resistance reading, but for some reason don't last very long, and in one case I came across, didn't work at all. On these automotive engines, (4.8, 5.3 & 6.0) using AC Delco knock sensors is the way to go.

Another thing, did you clean the threads before screwing in the new sensors? You should run the proper thread tap into the hole to clean out and rust and debris before installing the new sensors.
Click to expand...

The sensors I bought is this:
http://www.hansenkatalogen.se/sv-SE...#/marine/code/dd1/y/71/1/31251/1713125118897/["17230"]

But they have'nt worked at all after changeing

I just unscreewed the old ones and replaced them with those.

No cleaning or so.
Is there a way to test my new sensors when they are mounted? Feels quite stupid to check everything else if my new sensors are broken from the begining.

//Stefan
 
How do I clean the threads?
What type of cleaningmedia do I use?
 
As your title states "Code 44 Cannot Detect Knock Sensor" for MEFI 3 would mean the ECM lost the signal from the sensor. So either the electrical connection is broken or open circuit or the knock sensor is faulty. If the ECM was detecting continuous knocks you would see Code 43. It is critical that you replaced the knock sensor with the exact sensor part number that you removed. Also, per the manual, it very important that the knock sensor be torqued to the precise specification and that incorrect torquing will result in unsatisfactory performance - torque to 12-16 lb-ft.

If the sensor is the correct part number and installed properly you should start performing continuity testing on the wiring.
 
I tested both sensors with a multimeter and gets exactly 103 ohm at both sides.

I also tested the wireconnectings on each side by putting one side of the multimeter in the wire and the other side to ground.
I got exactly 3,78 volt on each side with motor turned off and just using the ignition.

In my world that seems to be 2 good sensors and 2 good connections between sensor and ECM.

How is it possible that it dont works while I drive???
 
There is more to the knock sensor than just the resistance reading.

The aftermarket sensors for the GM automotive engines showed something similar, the resistance readings were exactly the same as the AC Delco sensors, but they just didn't work.

I'm not saying that this is the cause of your problem, but just realize that this is not the place to be using aftermarket parts.
Make sure that you have the correct oem sensors.

Use a thread tap of the proper size to clean the threads.
As stated above, proper torque is critical for a knock sensor to operate properly.
 
I've done more testing.
When I use the multimeter between connector and ECU and ground I get a value of 1,06 volt on each side (I wrote 3,78 before but that was incorrect)

When I connect the sensors and do the same test the right sensor still shows 1,06 volt but the left says 0,22???

Does anyone knows what that means?
 
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