496HO Freeze Frame... who can read this?
03-14-2012, 10:38 PM
#11
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Check your ground cables everywhere starting at the battery to the bellhousing studs at nine and three-o-clock.
I had this symptom once and it was the digital (three wire) trim limit sender - not to be confused with the trim sender for the gauge. I realize you're not seeing trim faults in the freeze-frame.
It acted just like it was starving for fuel and a tiny bit random until you bumped the throttle up at dead idle, in gear. See if you can drive it around with the computer connected (again) and duplicate the symptom in the active faults section.
Some faults will appear and disappear quickly; sometimes they will not leave freeze-frame info. It's not supposed to happen but it has happened before.
I had this symptom once and it was the digital (three wire) trim limit sender - not to be confused with the trim sender for the gauge. I realize you're not seeing trim faults in the freeze-frame.
It acted just like it was starving for fuel and a tiny bit random until you bumped the throttle up at dead idle, in gear. See if you can drive it around with the computer connected (again) and duplicate the symptom in the active faults section.
Some faults will appear and disappear quickly; sometimes they will not leave freeze-frame info. It's not supposed to happen but it has happened before.
Last edited by SDFever; 03-14-2012 at 10:40 PM.
03-14-2012, 10:52 PM
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Stalling in gear can also be code # 110 Shift switch - ecm can see it as critical and can reduce the engine to only 5 % available power and or the shut down. Early early 496's did not have a swift switch but I think off the top of my head 2003 or 2004 and up does. This switch as a fault or even a fault that does not show up will indicate neutral at high speeds and high loads while in gear. Problems - the switch not adjusted properly or loose, wiring problem related to the switch, and linkage not adjusted properly.
Also I would not rule out low water pressure or the water pressure switch itself or would NOT rule out the ECM and or its grounds or pin connections. Also agree with Raylar about connections & grounds. Low or high battery voltage the ECM sees this as critical so check that out also.
Good luck but I would have to say these kind of the problems it is alot wiser to take it to a boat shop that sees alot of 496's. We see alot of 496's and sometimes they can eat your lunch.
Also I would not rule out low water pressure or the water pressure switch itself or would NOT rule out the ECM and or its grounds or pin connections. Also agree with Raylar about connections & grounds. Low or high battery voltage the ECM sees this as critical so check that out also.
Good luck but I would have to say these kind of the problems it is alot wiser to take it to a boat shop that sees alot of 496's. We see alot of 496's and sometimes they can eat your lunch.
Last edited by BUP; 03-14-2012 at 11:12 PM.
03-14-2012, 11:05 PM
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Oh forgot your 3 or 4 codes from post 1 means nothing as they are set for smartcraft. Most people see pitot chk hi or lo and think thats the problem One pitot will not set off a warning horn and two the pitot pressure sensor is used for boat speed and if it was a true fault - 100% power would still be available. Good luck
Last edited by BUP; 03-14-2012 at 11:13 PM.
03-14-2012, 11:15 PM
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You said the previous owner replaced the manifolds,risers,& starter ?I think I would take SDFevers advice & start looking at grounds maybe even something like ground wires reinstalled in a different order causing intermittant loss of ground. You know how merc likes that black paint nice & thick. Or maybe a pinched harness ? Just a thought, Randy
03-17-2012, 10:25 AM
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Markmysite:
Slow down there partner!
Lets not start spending your money and time here replacing parts that may not be bad and confusing the real issue of whats wrong!
Lets go thru what we know and what is being recorded in the ECM.
First, Pitot, Fuel Level1 & Fuel level2 and Sea temp will always show up in this PCM555 for the 496 engines unless the Mercury devices anre installed in the boat and connected via a smartcraft connection. they don't mean anything in this case and they will not institute a guardian event.
Second, when a Merc 496 stalls in gear it will usually always throw some codes like crankshaft, camshaft, sometimes the MAP and the TPS. These will sometimes occur even though there maybe nothing wrong with these sensors. If these sensors are bad they will always usually throw a fault code with continued operation of the engine and its not common for the failure of these sensors to be intermittant, especially three at once. The negative sea temp of -29 degrees or so is a default reading becuse the Merc sea temp sensor is not installed or being used.
The TPS sensor fault showed up once when you hit the Rev-limiter at 5150rpms as recorded and that does not surprise me that a sensor code showed up at that point.
You or your mechanic can check the TPS voltage very easily with the key on engine not running. The scan tool will show it or you can read it across the blue wire to the black wire at the TPS harness just after the TPS connector. The scan tool also outputs the throttle open percentage which is derived from this voltage range. (0-3% to 97-99% ) Voltage should be about .56-.58 volts at idle and as you advance the throttle to full open it should go up to about 4.25-4.5 volts max. with a fairly smooth rise on a smooth throttle operation. If the voltage does not jump around, drop suddenly during throttle advance and is close to these ranges, chances are the TPS sensor is just fine.
You are saying that the boat operated just fine today even with diagnostics hooked up and no codes were present and active. I know frustrating, but it does happen.
You have to remember that with boats there is the Performance boaters law and there is Murphy's law. Performance boaters law reads: Murphy was a phuck'in Optomist!" You need a good laugh at this point!
Your mechanic measured fuel pressure under load and that showed approximatly 40 psi w/vacuum signal to the fuel pressure regulator and that would indicate that fuel pressure is not an issue. Also since this was measured under a good load and the engine is stalling at 1000-1200rpms it does not seem to be a fuel issue since at that rpm , the engine does not need a lot of fuel flow.
You could be seeing some intermittant connection that is basically dropping the engine out or off causing the stall and since the guardian will only usually stop the engine with severe overheat, super low or no oil pressure, then when you are loosing the engine at low rpms I doubt the guardian is shutting the engine down.
I believe you mentioned you may have already replaced the IAC so that should not be an issue since you are getting no fault codes for that. Normally when an IAC is going bad or failing it can cuase a 496 to stumble and stall when transitioning from higher rpms to lower rpms near idle as that is what it does. It is designed to open quickly and close to keep the transition rpms stable and smooth back to idle with the extra shots of air it feeds the engine bypassing the throttle blade and keeping a smooth decelleration.
The water pump and water pressure does not seem to be a problem from the events logged as it shows about 30 psi when the engine was at 5100 rpms and the engine coolant temperatures at that high rpm only show 167 degrees which is a very good cool operating temperature for this engine.
What does this leave: well we really need to have the history read outs from the ECM, because in those we may see a recurring problem that can be seen happening previously and at several times that you experienced the problem. If there was a guardina fault event that stalled the engine it should be recorded in the history file in the ECM. If its not showing up in those history files then I would say its probably something like a loose electrical connection, could be at the helm in a key switch, lanyard, etc., low battery voltage when operating, bad or loose ground connections, bad or fouled spark plugs, or possible loose or corroded connections at coil harness plugs, fuel injector harness plug or lets hope not a faulty wire in the engine harness somewhere.
The only real good news at this point is for now it seems to have stopped and there is a possibility it will never happen again, I've seen that happen before and we use the old reply there" If it ain't broke, don't fix it " approach.
Hope some of this info help you look for your problem and understand some of the systems the 496 engine and Ecm use.
Best Regards,
Ray @ Raylar
Slow down there partner!
Lets not start spending your money and time here replacing parts that may not be bad and confusing the real issue of whats wrong!
Lets go thru what we know and what is being recorded in the ECM.
First, Pitot, Fuel Level1 & Fuel level2 and Sea temp will always show up in this PCM555 for the 496 engines unless the Mercury devices anre installed in the boat and connected via a smartcraft connection. they don't mean anything in this case and they will not institute a guardian event.
Second, when a Merc 496 stalls in gear it will usually always throw some codes like crankshaft, camshaft, sometimes the MAP and the TPS. These will sometimes occur even though there maybe nothing wrong with these sensors. If these sensors are bad they will always usually throw a fault code with continued operation of the engine and its not common for the failure of these sensors to be intermittant, especially three at once. The negative sea temp of -29 degrees or so is a default reading becuse the Merc sea temp sensor is not installed or being used.
The TPS sensor fault showed up once when you hit the Rev-limiter at 5150rpms as recorded and that does not surprise me that a sensor code showed up at that point.
You or your mechanic can check the TPS voltage very easily with the key on engine not running. The scan tool will show it or you can read it across the blue wire to the black wire at the TPS harness just after the TPS connector. The scan tool also outputs the throttle open percentage which is derived from this voltage range. (0-3% to 97-99% ) Voltage should be about .56-.58 volts at idle and as you advance the throttle to full open it should go up to about 4.25-4.5 volts max. with a fairly smooth rise on a smooth throttle operation. If the voltage does not jump around, drop suddenly during throttle advance and is close to these ranges, chances are the TPS sensor is just fine.
You are saying that the boat operated just fine today even with diagnostics hooked up and no codes were present and active. I know frustrating, but it does happen.
You have to remember that with boats there is the Performance boaters law and there is Murphy's law. Performance boaters law reads: Murphy was a phuck'in Optomist!" You need a good laugh at this point!
Your mechanic measured fuel pressure under load and that showed approximatly 40 psi w/vacuum signal to the fuel pressure regulator and that would indicate that fuel pressure is not an issue. Also since this was measured under a good load and the engine is stalling at 1000-1200rpms it does not seem to be a fuel issue since at that rpm , the engine does not need a lot of fuel flow.
You could be seeing some intermittant connection that is basically dropping the engine out or off causing the stall and since the guardian will only usually stop the engine with severe overheat, super low or no oil pressure, then when you are loosing the engine at low rpms I doubt the guardian is shutting the engine down.
I believe you mentioned you may have already replaced the IAC so that should not be an issue since you are getting no fault codes for that. Normally when an IAC is going bad or failing it can cuase a 496 to stumble and stall when transitioning from higher rpms to lower rpms near idle as that is what it does. It is designed to open quickly and close to keep the transition rpms stable and smooth back to idle with the extra shots of air it feeds the engine bypassing the throttle blade and keeping a smooth decelleration.
The water pump and water pressure does not seem to be a problem from the events logged as it shows about 30 psi when the engine was at 5100 rpms and the engine coolant temperatures at that high rpm only show 167 degrees which is a very good cool operating temperature for this engine.
What does this leave: well we really need to have the history read outs from the ECM, because in those we may see a recurring problem that can be seen happening previously and at several times that you experienced the problem. If there was a guardina fault event that stalled the engine it should be recorded in the history file in the ECM. If its not showing up in those history files then I would say its probably something like a loose electrical connection, could be at the helm in a key switch, lanyard, etc., low battery voltage when operating, bad or loose ground connections, bad or fouled spark plugs, or possible loose or corroded connections at coil harness plugs, fuel injector harness plug or lets hope not a faulty wire in the engine harness somewhere.
The only real good news at this point is for now it seems to have stopped and there is a possibility it will never happen again, I've seen that happen before and we use the old reply there" If it ain't broke, don't fix it " approach.
Hope some of this info help you look for your problem and understand some of the systems the 496 engine and Ecm use.
Best Regards,
Ray @ Raylar
It seems like the problem has gone away for now. We took it out for 3 hours yesterday without any Guardian alarms or engine issues at all. Perhaps it was some of the old gas and varnish still in the lines or clogging up a sensor or something. I had ran Lucas and Stabil through it once before draining the tank and changing the filter. I then put new gas and ran Techron through it this time. Maybe I just needed to run it longer? It could've been a wire connection, ground or something too... and it didn't jar loose this time... who knows. I will go back over the whole thing and check them all more thoroughly though. I'm just glad I was able to take my guests out and not have to limp her back home the 1 hour drive down my canal.
Appreciate the tips everyone has given me. It's helping me to learn more about his engine... esp the PCM. These EFI's are not like dealing with a carb engine... that's what I'm used to dealing with.
Last edited by Markmysite; 03-17-2012 at 10:28 AM.
