Knock Sensor fault code (DTC)

[Brucetheshark]

Long story (sorry), hopefully the history is useful:

I'm the second owner, bought a 2006 196 in 2020 with 412 hours, it now has 486 hours.
When I bought the boat in 2020, the original owner's Nautique dealer had recently replaced the knock sensor and changed the oil.
During the six years I've owned the boat the MEFI set the Knock DTC several times.
Sometimes coinciding with a low fuel warning, which can happen at 1/4 tank, ~10 gallons.
Engine runs great under all conditions, even with low fuel or knock alarms.
Maintenance history:

• 2020 replaced plugs, plug wires, distributor cap and rotor, and still got KS DTCs when skiing and idling in turns if < 1/4 tank.
• In 2020-2021 listened for knock at idle and mid throttle in neutral using a stethoscope with cup replaced by metal rod. Nothing heard.
• April 2021 at 449 hours, replaced both fuel filters (very dirty), drained the tank and added 100% gas. The fuel drained from purchase turned out to be old ethanol fuel, which at the time I assumed was the root cause of the KS DTC.
• Every fall I drain the tank and plug the fuel vent port for winter storage in my heated garage.
• Spring 2024 at 476 hours, I replaced both fuel filters just due to age, drained the tank and added 100% gas.

The MEFI did not set a KS DTC after the fuel and fuel filter change in Spring 2021 to winter storage 2025.

Winter 2025/26 repairs and test drives:

• Drained the tank as usual, removed the instrument panel, repaired Faria gauges, replaced original Perfect Pass with Stargazer, unplugged and re-plugged the MEFI-4b electrical connectors to confirm version, replaced boat battery, removed and re-sealed fuel tank fittings for supply, return, vent due to fuel odor from prior owner using ethanol. Added 10 gallons 100% gas from no-brand local station.
• May 2026 launched boat, 1/2 hour 4 mile idle cruise to my dock. MEFI did not set a KS DTC.
• June 19, 2026 half hour idle cruise MEFI set a KS DTC.
• June 20 added octane booster (later read PCM manual that states not to do this), ~1 hour test drive at idle and 30mph, MEFI set KS DTC at end of drive.
• June 21, 2026, drained fuel tank, added 17 gallons of BP 100% gas (7/8 tank on gauge). Fuel drained sitting in a plastic tub got rained on and turned gold, meaning it had ethanol.
• June 24, 2026, 10 minute idle cruise to ski buddy's house, no KS DTC. First ski run MEFI set KS DTC after hole-shot.
• June 25, 2026, test runs using full power starts, MEFI set KS DTC on 8th hole shot.
• June 27, 2026, visually checked fuel filters, look clean.

Scratching head......
Next #1: check wire continuity from KS to MEFI (not likely an issue)
Next #2: ordered new KS, arriving July 3rd.
TIA,
~Bruce

[JayG80]

Have you checked the cam retard after the pcm service bulletin was published? No Teflon tape on is threads? I'd assume dealer checked both but you never know.

https://www.planetnautique.com/vb5/f...2008-343-excal

#SUP2003-06
PCM Service Update Information on Setting CAM Retard

This is an informational update in order to provide you with some information that may assist you in setting the CAM
retard on ALL 2002-2004 PCM 5.0L (Pro Ski) and 5.7L (Excalibur) engines.
This parameter MUST be 43-47 degrees or driveability problems will exist. Some of the symptoms, but
not limited to, are as follows:
• Backfi re
• Loss of power
• Sluggish
• Hesitation
In order to properly set the CAM retard, one of the following scan tools MUST be used:
Hand-held Scan Tool: PC Based Diagnostic Software:
Rinda Techmate Diacom

Important: The basic principle that the distributor must be installed into the engine properly still exists. If the proper
CAM Retard cannot be achieved, check the installation of the distributor.
Engines Affected: 2002-2004 5.0L MPI (Pro Ski) ALL Model Number: Last Digit “M”
2002-2004 5.7L MPI (Excalibur) ALL

[Brucetheshark]

Have you checked the cam retard after the pcm service bulletin was published? No Teflon tape on is threads? I'd assume dealer checked both but you never know.

https://www.planetnautique.com/vb5/f...2008-343-excal

#SUP2003-06
PCM Service Update Information on Setting CAM Retard

This is an informational update in order to provide you with some information that may assist you in setting the CAM
retard on ALL 2002-2004 PCM 5.0L (Pro Ski) and 5.7L (Excalibur) engines.
This parameter MUST be 43-47 degrees or driveability problems will exist. Some of the symptoms, but
not limited to, are as follows:
• Backfi re
• Loss of power
• Sluggish
• Hesitation
In order to properly set the CAM retard, one of the following scan tools MUST be used:
Hand-held Scan Tool: PC Based Diagnostic Software:
Rinda Techmate Diacom

Important: The basic principle that the distributor must be installed into the engine properly still exists. If the proper
CAM Retard cannot be achieved, check the installation of the distributor.
Engines Affected: 2002-2004 5.0L MPI (Pro Ski) ALL Model Number: Last Digit “M”
2002-2004 5.7L MPI (Excalibur) ALL

Hi Jay, thanks for the info. I previously used Teflon on the KS per the MEFI-4b manual, and in 2020 checked continuity between KS housing and ground. I removed the Teflon yesterday, but haven’t test driven it yet. I’ll update asap. Don’t know what to say about the CAM Retard TSB, but the boat runs great, I don’t have any of the symptoms listed.
~Bruce