Engine Knock Sensor on 2007 SAN 220

[John Garcia]

Hi Everyone. Newbie here with a 2007 SAN 220 with a PCM 330. It has about 350 hours and I recently bought it. Ran great for a week and then I took it out today after putting in about 20 gallons of premium from Shell and when I get to about 20 MPH the "Engine Knock" sensor goes off. At less than 20 MPH I don't get any errors, but three times at about 20 MPH it went off. Engine is running great, oil pressure good, temp is good, and everything else seemed ok. I called the local dealer and they said it may be bad gas and that I should add some "octane booster" and add some other gas. I would love to hear everyone's thoughts. Thanks, John

[Nautiquehunter]

Since the problem started right after the Shell gas was added it sounds reasonable to think its bad gas . You could go back to the Shell station and ask in they had any other complaints. I would add some marine Stabil and add as much good gas as possible . After a tank or so see if the problem goes away.

[John Garcia]

Thanks for the advice. I added some octane booster, but will add the Stabil as well. Good idea to call the Shell station as well. They are a bit far from my house, but worth a shot. I will let you know how it goes. Thanks, John

[AirTool]

I don't see how on earth gasoline could affect the knock sensor when the two never see each other. The know sensor screws into the water gallery because water is an excellent conductor of noise and the water surrounds the cylinders where said knock would occur.

The warning light (MIL) coming on is not related to how much knock there is but instead a faulty knock sensor, faulty connector, or faulty re-installation after winterization. The knock sensor cannot be damaged by the fuel.

[John Garcia]

Thanks for the input. Just so I understand. The knock sensor error code only comes on when there is a fault in the knock sensor and not when there is an actual "knock" in the cylinder? Thanks. John

[AirTool]

Thanks for the input. Just so I understand. The knock sensor error code only comes on when there is a fault in the knock sensor and not when there is an actual "knock" in the cylinder? Thanks. John

There is often "knock" in the cylinder from pre-ignition. That is what the sensor detects and then the ECM makes adjustments to reduce or prevent knock.

I have a hard time believing that the code will throw for excessive knock. I've never seen that before and heard plenty of knock. Further, if you hear it...it is way past the typical levels the knock sensor can detect.

There are more details on this new thread....you should follow it.

http://www.planetnautique.com/vb3/sh...k-sensor-issue

[TRDon]

I spoke with someone at cc when I was having my knock sensor issue. I was told that if there is a problem with the knock sensor and it isn't seeing any knock at all at any range, it will throw a code, with the computer thinking it is malfunctioning. If there is excessive knock, pulling more than 5 degrees for x amount of revolutions, it will throw a code.

He reason for the gasoline having a direct relationship with the knock sensor code is if there is a bad tank of gas, or too low of octane, it will start knocking and possibly get to that threshold I mentioned. It is an indirect relationship in the sense that it doesn't physically touch the sensor. I can't say who at cc I talked to about that, it was last spring.

[John Garcia]

Thanks. This makes a lot of sense. I am bringing it into the shop tomorrow to have them take a look just in case. I will let everyone know what they have to say. Thanks again. John

[John Garcia]

Hi all. Thanks for all of the help. Looks like one of the wires had simply come off of the knock sensor. Kind of odd given that it had been used all summer, but oh well. Thanks for the advice. John