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2006 BF225 Knock sensor replacement ??

5

52ecgary

Member
After having alarmed does a knock sensor reset or need to be replaced? Mine alarmed after having gotten water spray, but continues to alarm around 5100 rpms after the water line was replaced.I cleared the code but it alarmed again at 5100rpms and the check engine light stays on.
 
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The knock sensor is a tricky one simply because it is situated beneath the intake manifold. The workshop manual will tell you to remove one cylinder head to replace it, however with a little ingenuity I have managed to replace the only one I ever had to change without removing a cylinder head, with the help of an assistant and a lot of patience. As you have had water spray on it, it is possible the plug may be green, if you run in saltwater. In this case you will need to remove the harness in the valley in it entirety to clean up all the contacts.
 
Ian, thanks again , any chance I am misinterpreting the code, two intermediate then 3 short ? Or is there a way to verify that it is actually the knock sensor ??
 
I don't believe you are misinterpreting, there is a 3 for map sensor but no 20, so I am guessing you have it right. Try clearing the code, then run the engine up to 3000 rpm, no load for 10 mins, then rev to 3500 for a further 10 secs and then recheck for faults, if 23 returns then the knock sensor is disconnected/corroded, if not then carry out a continuity check of the blue/red wire between the knock sensor and the ecm. See how you go with that, it is not going to be easy because or where the sensor is situated.
 
Thanks Ian, I ran for 15 min at 1500, 10 min at 2500, then 3 min at 3600 before it alarmed. switched off then immediately back on, ran 3 min and then alarmed.I will attempt to check connections tomorrow.
 
HondaTech support (via dealer in Ga.) suggests crank shaft wobble, and knock sensor is functioning properly. I'm in hopes that the seller is a man of integrity if this is the case, I've gotten no use from this purchase to date!! Other less likely possibility is fuel pressure, hope for the latter.
 
Not sure about that one, if the knock sensor detects a knock it retards ignition timing, not set an alarm. If you look at knock sensor faults in the manual it does not mention alarm when knocking. It does however alarm if the ecm detects that it is disconnected or not functioning, thereby putting the engine at risk if detonation occurs
 
Did you pull codes again after your tests? If so, what code(s)? If not, you should.

This is the first post on this forum in my memory where there was a problem with the knock sensor on the 225. You stated on your first post that this problem started when you got water spray in your engine compartment. I think you need to spend the time to pull that harness and check/clean all of the connections as Ian recommended. Then check the wire from the sensor connector to the ECU. It is pin 7 on the 26 pin connector. According to the shop manual the knock sensor wire is red/blue.

I also suggest that you check end play in the thrust washer by gently prying up the flywheel and precisely measuring the end play. Not sure what the max allowable is. Ian probably knows. I suspect that too much end play could also activate the knock sensor.
 
Check crank end play but I stand by what I said and what Chalk said, I have had several motors with different types of internal knocks and have yet to have a knock sensor fault code as a result of those noises.Check your wiring from the knock sensor all the way to the ecm, you will find an issue, if not then it's either the knock sensor itself or the ecm.
 
Thanks CHawk & Iang, I hope it is in the wiring/knock sensor and will try those things you suggest. Honda support said tolerance was .00186 which I can't measure, but wiring checks can be done. I will post outcome in a couple of days, your help is much appreciated !!
 
I've exhausted my skill level, pulled breather and could barley see knock sensor and I don't want to pull a head to replace something that probably isn't broken,put it back together and now no pee stream, could I have pinched a water inlet somewhere, the impellers are 3 months old and was peeing well before although I did come thru shallow water while loading on the trailer. Any ideas?
 
It's possible that when you reassembled and replaced the starboard upper cowling, you failed to reconnect the hose to the indicator, pinched it, or it came loose. Pull that cowling and inspect. I would not run the boat until you do that because you may flood the engine compartment.
 
Also, when you pull that starboard upper cowling, pull off the indicator hose and run a piece of string cleaner filament or heavy mono through the hose, and also at the connecting nipple on the water jacket to clear any debris. You can run the engine briefly with the cowling loosened or removed in a test tank to see if you have cleared the blockage, if any.
 
I don't understand that. You should get water out of the flush line if it's disconnected while engine is running. But you should NOT use the flush line when the engine is running. If no water out of the indicator on muffs, while engine is running, you have a blockage or the water pump has totally failed.
 
Back flushed after removing t-stats, put on muffs and began to get a slow but increasing flow(engine running), will continue flushing today before re-launching.
 
Sounds good. Let us know the results.

If you can get back to the pee stream after you are up to operating temperature, it should feel warm but not really hot. Better yet, hit the manifolds with an IR gun. You should read about 160 degrees F.
 
Today I replaced the impeller, removed t-stats and got a weak flow on muffs, not sufficient to cool engine. I will reevaluate the possibility of a kinked line around the VST, where I replaced the split water input line to the VST, which was the beginning of this debacle.
 
You're not going to get a strong stream on muffs. In fact, if you are on muffs for more than a few minutes, you are very likely to get an overheat alarm. Muffs on a typical garden hose do not provide enough water to adequately cool the engine. At least that has been my experience. Drop the lower unit into a large trash can filled with water to the top (over the anti-ventilation plate) for an adequate test.
 
I removed lower unit and t-stats, flushed aggressively, verified impeller rotation, reassembled and got good flow. For now I'm going to let the knock sensor rest assuming it to be an open circuit, thanks to CHawk, iang,and all who have helped!!!
 
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