Knock sensor code

To start with I own a 2005 Honda bf150a with 290 hours. I have been fighting an issue all summer long, being that first starting out right after the battery has been connected, starting and taking off the motor will rev up all the way to around 5500rpm. It will stay there and run great but only for a few minutes. Then it will bog down and buzzer will sound and check engine light comes on. It will stay running but only to right about 4000 rpm. I can shut the engine off and restart and the check engine light will be off but will still only rev to 4000rpm. After 5 minutes or so the buzzer and check engine light come on again.

If I read the dtc code it's 23-1, which shows to be for the knock sensor. I have cleared it and it comes back the same as just disconnecting thr battery. I have read the factory service manual for the code and have ohmed the wire out and it's good to the ecm.

Could the knock sensor actually be bad, or could another sensor be the issue like 02 sensor (I have seen certain Hondas are bad about going through them) I have changed all fuel filters, spark plugs, both thermostats and impeller.

Hi,
Not a regular tech working on these myself so don't take this for "gospel".

The info I'm looking at says that the 23 code is a knock sensor code and the -1 indicates "an open circuit in sensor ground line (green/red)".

I know you said that you ohmed the wire but that is not always a reliable way to test a wire's current carrying capability. A better way to check multi-strand wiring would be to load test using an incandescent lamp at one end and applying 12v at the other with the harness disconnected from the ECM.

If the link above works, it's a good tutorial from AllData. I prefer using a sealed beam headlamp bulb but there are options.

Remember to manipulate the wire (wiggle test) while obseeving the lamp.

If the wire and connectors check good then it' likely a bad sensor. While this could also be a fault with the ECM that would probably be a very rare occurence.

Good luck.

Sorry, the link from AllData didn't load correctly...I will try again.

Thank you. I will load test the wire to make sure it is good as a next step. The sensor is cheap enough to swap out just doesn't look like it's the easiest to get too. I may go ahead and order it and swap it if the wire test good and go from there.

Yeah, they make many of the sensors on these outboards very difficult to access.

Because corrosion is always a big deal in the marine environment, it's a good idea to carefully inspect the pins and sockets of any electrical connector you unplug. I recommend mechanically cleaning them if you can. I use special tiny nylon brushes to knock off any surface oxidation being careful not to open up the sockets so that the pin fit remains tight.
A good contact cleaner like De-Oxit will help too.

Hope you have success.