03 496 going into guardian mode with no codes help
 

Hello,
I have a 03 sunsation with the 496 mag. It is going into gaurdian mode first time i run during the day. Let it sit for ten min start it back up runs fine the rest of the day. I have a merc scanner and its saying guardian mode unknown. I have replace the sea pump houseing back flushed checked all fluids and everything is good. Talk to a few marines and they are stumped. Please help. Thanks Tom

Have you had the scanner plugged in during your first run ups to see if something is out of range when it is going into guardian mode? Sounds like a sensor like pressure or temp starting to fail but for some reason the code isn't being stored..

I am having the same type of problem. Mine will run fine but will sound the alarm and go into guardian mode intermittently when I am running 3500-3800 rpm. I have replaced the sea water pump, back flushed both the heat exchanger and the oil cooler but will still do it. As stated previously, I now think it is a sensor. As far as the guardian unknown, my scanner says the same thing. You need to go to Fault History on the scanner and then see if there are codes. Each time mine goes into guardian the history will read Overspeed, Guardian, and Lo BLK press (Low Block Pressure).

likely water pressure sensor. I've changed on 12 rigs this season already.

That is what I think it is also. Are they located on the oil cooler?

Iac

My 2c on the water pressure sensor? As tunertech points out they don't seem to like water.
On 03 engines the sensor is located on the sea water pump.

early 496,s had the sea water pressure sensor located on the sea pump,,they then ,moved to the oil cooler later

will agree with water pressure sensor, next IAC or shift in gear switch is either bad or out of adjustment.

Depending on serial # not year is where the location of the water pressure sensor and if this 496 has a shift in gear switch.

Early early 496 did not have a shift in gear switch but I think going off the top of my head 02 or 03 model year started them but again there was serial # break for the start of them on the 496.

Next and it is very important anytime you bring your boat in for repair to a true marine repair facility the 1st thing the mechcanic / tech does is logs your motor & drive serial # so he knows what parts app go on the motor /drive plus can check for SB's / PB's (service & parts bulletins) and what is the approriate service manual if needed.

The year of the boat / hull means nothing to the tech working on it. plus there is so many boats now in the market with motor swaps & repoed boats with mix match years & parts. Yes hull year model does help but everthing motor wise and drive wise and transom assembly all goes off of serial # FYI. Good luck.

well i guess i will replace the water sensor and try that. Whats a good site to order one from
Thanks Tom