Engine Alarms and Guardian mode issues

[Hoplite808]

Recently I rebuilt the top half of the 7.4 MPI and replaced entirely with a rebuilt drive the Bravo 3 leg on my 1996 270 Sundancer. I took her out for a Sea Trial after the repair and it only seemed to top out at about 3000 RPMs under load with a max speed of about 18 knots. But it ran smoothly for about 10-15 minutes. Then the engine began to run rough if I tried to throttle up but idled okay and a loud beeping alarm started to double beep from the console every 30 seconds or so. I shut down and checked everything on the engine and it all appeared okay. Limped back to my slip and then found the engine throwing code 12 and then found one of the wires loose for the sensor on the drive oil bottle. Plugged that back in and the double beep changed to a single beep and engine still wasn’t running quite right. Any thoughts on what is going on here?

 

[scoflaw]

So you have a scanner? That's a pretty basic ecm system and there's only a few sensors

 

[Hoplite808]

I have a voltmeter with a continuity testing function, a paper clip and the ability to count beeps is all.

Also oil pressure and water temp stayed normal the whole time. IAC and every other sensor except for the MAP on the back of the intake plenum have been replaced prior to this.

 

[scoflaw]

without a scanner you won't be able to see the sensor values. Oil, water would be a solid hard alarm. Your can't clear codes to see if they return with your paper clip.

Rough running engine could very well be unrelated to the alarm. Have checked your fuel pressure, looked at the plugs? Might be cheaper to put a new MAP sensor on it, scanners are expensive.

 

[Hoplite808]

From everything I’ve googled and looked through what manuals are available I can’t find a reference as to what a repeating single beep every 30 or so seconds would be trying to warn me about. Also if it has a guardian mode and it went into it because of the loose drive oil level sensor is there something that needs to be done to reset it back out of said mode?

 

[scoflaw]

No guardian with the mefi ecm's I believe code 12 is all is OK.

 

[techmitch]

No guardian with the mefi ecm's I believe code 12 is all is OK.

That's what it was with older GM OBDI cars also.

 

[Hoplite808]

I went down today and started going through everything found a random wire that I can’t seem to identify as to what it may have been connected to once upon a time that I guess had gotten it’s bitter end pinched Uber the exhaust plenum. When it grounds completely out it causes a steady alarm. Got that out of the way and cut off the mangled bit that had gotten smashed by the plenum and taped over the end. Alarms stopped entirely but engine seems to only run at half strength. Guess I’m going to have to start working my way through the ignition and fuel systems until I find the faults. It’s weird there would even be one as I replaced near about everything there.

 

[Bill Curtis]

OK, what color is the wire? Have you looked in the wiring diagram to try to match it up? It obviously goes to the ECM, since it alarms when grounded.

 

[scoflaw]

It's for either overheat, oil pressure, or low drive fluid, that's all that ecm has for alarms

 

[Hoplite808]

It’s Black with a white stripe. According to the schematic it’s the ground wire for the test plug. However with it connected to nothing the test plug is still grounded.