Another 496 alarm thread!!!!!
 

I went out yesterday for the first time of the season. I just installed a mechanical water pressure gauge and oil temp gauge. Drive it about an hour with no issues. As I get back to the dock I was getting the 2 beeps every minute. Put it on the trailer and flush on the hose, no beeps hummmm. I went out today and shortly after I left the dock the 2 beeps a minute returned. Drove around at my usual 3500rpm cruise. Good readings on gauges, oil pressure, oil temp, water pressure, voltage, exhaust cool, good flow out of pipes etc. Engine never skipped a beat. I had to pass someone so I went wot. After a short period the alarm went to a constant. So I backed down to an idle. Alarm went back to 2 beeps a minute most of the time. Getting close to dock later in day I went wot again, constant alarm returns ahhhhh. I don't think there was reduced power when it went to a constant alarm, although I backed right down. It didn't nose over at all.

I don't have a scanner YET. I was looking over the winter but kind of slipped my mind. Will be buying one shortly!!!!!

After doing some research on the alarm beeps of a 496 it leads me to the wp sensor.

Does anyone know the ohm reading vs pressure of the 496 pressure sensor? I would like to check to see if it this and get back on the water for memorial weekend.

Fwiw it's a 2002, I just changed the impeller and wear plates in the Hardin marine stainless water pump as I do at the beginning of every season, I checked every plug on the harness, no burnt wires or connectors, even the iac. The engine starts right up and idles fine.

The seapump sensor measures water inlet pressure or water block pressure. It is located
at the seapump inlet hose. Normal diagnostic tool ranges are 1-5 psi (7-34 kPa) at idle and
7-17 psi (48-117 kPa) at WOT. To check if sensor is within range, the diagnostic tool reading
with key ON should be approximately zero. The normal resistance value for the water pressure
sensor at 70 degrees F (21 degrees C) is A to B 31.5 kohms and A to C 42.9 kohms.
A malfunction of the seapump sensor will set the fault of Seapump CKT Hi, Seapump CKT


Pm me your email or cell # and I'll send you the 555 pcm troubleshooting Merc fsm.

PM sent

I have notice that Hardin kits now have a different impeller IMO it looks and feels and bends like a cheap made impeller. The other impeller they had or possible still do as well was more like the exact Merc impeller. I ordered some kits like I do and this year there was 2 different made impellers - one like the Merc Impeller and the other one inwhich I think is cheaply made. Cheap impellers do not flow very well as rpms increases. Just saying and something I noticed this year about the Hardin rebuild kits.

Anyways you can test water pressure with a psi style gauge in place of the sensor also you can use an air gauge to pump air into the water pressure by fabing a fitting correctly to do so and pump air into it - you can watch on the scan tool the psi change with the air you are pumping into it - does the alarm go away doing this testing ?

Next is you can test the Merc spec testing of water volume into a pal for 15 seconds to see if it matches the correct amount of water flowed volume. Search up here as I least have brought it about 5 times on how to do so and the output specs for volume.

You really need a scan tool and know how to use it plus know how to read it. The understanding of all parts from the scan, can lead you to your problem area.

IMO and throw out a really good guess with a dart on the board ---- POSSIBLE EMCT sensor and or EMCT OVERHEAT --- when was the last time you changed out the heat exchanger end cap gaskets as well. These gaskets will restrict water flow to the exhaust manifolds but your engine temps will be spot on normal good readings. When was the last time you changed out completely the engine coolant ???

Just an FYI, I have NEVER ever seen water pressure at correct dead idle for OEM bone stock ECM 555 and PCM 555 anything 3 psi and above. Never and I have scanned marine engines in the thousands.

John I changed the end gaskets and o rings last season. I changed the antifreeze 2 years ago.

I kept checking the exhaust manifold temp byfeel and they were just slightly warm to the touch.

I installed a tee for the new wp pressure gauge inline with the factory sensor at the back if the sea water pump. The gauge won't read at idle, I'm assuming because there is a small 25ft hose feeding the gauge and a lb or 2 won't get threw such a small line with that pressure., common from what I was told.

I get 3 lbs at 1100 and it jumps right up after that. At 3500rpms it reads 28 and at wot it was about 45. I forgot the readings between 1100 and

Thanks Ryan for the info and as always a big thanks John!!

your welcome water pressure sensors come is 2 different psi ratings - one is 100 psi and one is 50 psi you have to use the correct one per your app - it goes by engine serial number inwhich inreturn the cal in the PCM.

Also do not rule out a bad EMCT sensor(s) really need to scan the engine to read all parameters.

Also you might have more than 1 problem going on as well. Not saying you do but sometimes 2 different warning horns can mean that or one alarm is soft alarm and then it turns into a hard alarm ( the same fault) The same works with guardian mode and available power..

Also there is 4 or 5 different diagnostic manuals for the 496 thru out the 10 year run of them in the marine world.

The first couple of service manuals really were average at best.

Update

I checked the ohms of the emct's and they were correct. Checked wp sensor obm reading and it was pretty far off. I went to local mercury dealer and got new sensor per serial number. Checked ohm reading on new sensor, just about the same as the old sensor. Installed the new sensor because I'm sure they wouldn't take back electrical part, still the 2 beeps.

Going to order a scanner Tuesday morning. Don't want to just keep throwing parts at it.

John I know you are spot on with your info. I'm thinking the emct sensor/s are a good possibility. Just confused the sensors have the correct ohm reading.

If I unplug the emct's will the alarm go away or be constant? The emct's can throw both the 2 beeps and constant beep. I'm almost tempted to pick up 2 new emct sensors, at least they are cheaper than the wp sensor lol.

Without being able to scan the PCM it's just a wild guess at this point. FYI when I had a bad IAC it had the same symptoms as you have right now. It had a 2 beef soft alarm at anything under 4000 RPM. Anything over 4,000 it would throw a constant hard alarm. Only visible sign the Iac was bad was when it was removed the pentil was in a different position versus the new one. Getting the scan tool should get you on the right track.

It's funny that you mention the iac. I recently lowered my idle rpm because it was a little high. I turned the stop screw 1/4-1/2 turn. I wonder if this has anything to do with it???? It ran for about an hour mostly at cruise before the alarm started going off?

John not picking on you but your last post - HUGE details that were left out from the start. Very important to tell all what you did to your engines before and during when they have problems and in full details plus what exactly you have for engines and set up - OEM stock or not. .

Anyways the throttle plate setting also effects the IAC PWM % and the TPS outputs along with IDLE control. So possible the cause of the problem but not 100 % without a scan and see those parameters.

Also now reading into your whats going on in more details - Possible IAC sensor or another sensor fault (2 beep ) that is putting the engines into guardian mode and by continue running the engine at half throttle or above settings or whatever throttle setting depending on available power % will activate the OVERSPEED fault. - hence the solid WARNING horn. I would bet that you will see OVERSPEED fault(s) in the scan matching the timeframe of the 2 beep warning fault,

No offense taken John!!!! I messed up for sure. Lowering the idle rpm completely slipped my mind, to much mind clutter.

I will be ordering the techmate pro first thing tomorrow morning.

Just a thought and please don't flame me too much, if I raised the idle back to where it was could the alarm stop going off if it in fact was the cause of setting the alarm? I'm not going to run it till I get the scanner,was just wondering.

forgot your app stock and all the fuel system and throttle body - I remem you have a drag car that runs on E 85. But forgot about how is 496 set up ??

next why did you have to lower your idle in the first place ? Did it raise by itself for whatever reason or did you raise it at some point in time and now had to lower it ?

What is your idle rpm now and what was it before ? I would rather know true rpm thru the scan tool than a dash tach - what gauges - do you have smartcrat gauges ???

Good memory John! E85 street car and bone stock 2002 496.

Just before i purchased boat in September 2012 the iac was changed. Don't remember idle rpm when I bought it but it seemed to raise itself a little over time. When I bought it it was very smooth going into gear. With the higher idle it was not as smooth. I know bravo's don't like to much rpm with shifting. With the recent lowering of idle it was smooth again. I think it was idling at 800 on stock Liviourse tach. From my reading a 496 should idle about 650.

Idle is about 700 on stock tach now, no smart craft gauges.

Idle has to be tested at fully warmed up 100 % reading the correct water temps within specs. it should be at 650 rpms using the scan tool and you can verify the engine temps with the scan tool as well to compare that against the dash gauge.

800 rpm too high for a stock app.

Possible throttle cable and or its adjustment

Vac leak

do you have stock flame arrestor and a very clean one at that ?

IAC muffler ??? a clean one installed and cavity clean and unrstricted and the long hose going back to the IAC ???

Also IAC gasket seal LEAK - hopefully new gasket was installed on very clean surfaces for the IAC itself the last time it was changed.
Also brand of IAC and its PWM readings at idle and start up

engine serial number ???

and this week killed me, first day off this whole month and people still bringing me boats this mourning. Jeez

Yes engine completely warmed up. Again going by factory tach as that's all that i have.

I checked throttle cable adjustment. The tb shaft was against the stop screw. I bought the shift cable adjustment tool as well. (I don't take short cuts. Try to do everything by the book)

No vacuum leaks.

Stock arrester that is cleaned several times a year. New iac filters always as part of my routine maintance. Hose is straight with no obstructions.

I'm pretty sure it is a Mercury iac (matching black] as the gentleman I purchased boat from was also very anal and took it to a merc tech. New gasket as well. I can always remove iac and replace gasket (after I get scanner). No iac readings on scanner YET. Will have by end of this week on my new scanner.

Serial # 0M084752

Hour meter has 420 hours now, purchased with 275ish hours. First problem that has come up for me. I have only done maintenance up to date. Very pleased with engine and boat. Before I purchased boat, Velocity went over it as they were going to broker boat. When I called Velocity to purchased tabs and steering I was told it was a solid boat.

John just a side question, does the diacom software do a lot more than the techmate pro? From what I can gather it will log and export unlike the scanner. This will only be used by me for the most part. I'm leaning toward the scanner. I know you have both.

Also over the years I know you were selling off your service manuals. I currently have number 30. Is there a better one to have?

Thanks so much for taking time out of your busy schedule to offer your help. It is greatly appreciated!!!!

I was giving you a hard time about the shift cable tool last time about making it instead of buying it but you took me wrong, totally unstandable and all water under the bridge after the fact. I remember that but will add I was talking about the throttle cable in above posts just saying.

Diacom techmate pro IMO is better for testing while lake running - I velcro it to my arm so I can drive and watch it. Also no laptop needed as it is just one simple plug and play. BUT the DIACOM SOFTWARE has a better diagnostic layout and can show more along with more capabilities, I have both to do what is needed for however. IMO the person who is not going to perform scans day in day out or even once a week - the techmate pro is a very good to have.

the 496 has 4 different engine side manuals thru out starting in late 2000 - IMO I would own that one and the next 1 or 2 after that - the NON catalyst ones if I was going to work on your own 496 app, The earlier 496 's some of the material does not apply in the later manuals but if you had to changed some parts that are NLA parts to current part offered - those manuals sure will come in handy.

John I totally forgot about making the shift cable tool. Like I said you have a good memory. Lol At the time I just bought a milling machine and wanted to use it. But reality set in and I just bought one. Sometimes I need to be shown the light. I didn't mean anything about buying the correct tools. Just stating I bought quite a few tools that will probably only get used once. They are building fast :)

Yes I knew you meant the throttle cable. I went over everything. All is good.

Thanks for the info on the scanner and manuals. I'll be purchasing the techmate pro first thing in the morning. I'll also keep an eye out for the other manuals.

Thanks again for the help.

I've had 2 boats both had same problem. It was the tube that brings the water into the boat clogs up after time and has to be replaced. you have to take off the lower unit follow the intake hose and there will be a plastic fitting that clogs up. a real pain to change.

Thanks big lock. I purchased scanner this morning and should be here Thursday. I'm going to scan it before I do anything else.

I received the Techmate Pro scanner today.

Had 5 fault codes in history: 94 pitot pressure, 75 fuel level, 118 steering, 131 trim and 191 fuel level which all should be BS codes.

In the freeze frame had 5 also

1) 9 Engine Gaurdian at 4254 rpms available power 89%

2) 19 Maximum RPM Execeeded at 4247 rpms with 89% power available

3) 77 Camshaft sensor fault at 214 rpm at 406.9hrs

4) 132 Crank Position engine speed 214 rpm at 406.9hrs

5) 152 IAC Output
809 rpm, throttle 0%, block pressure 2.1psi, battery 13.8, available power 20%, fault freq count 6#

With engine warmed up idled at 700rpm, available power 89%, guardian mode not specified, TPS .60volts, IAC duty 99.9, sensor power 5.0volts, operation mode-idle, guardian state 2#

While raising the idle with throttle handle the IAC duty will stay 99.9% up to about 925rpm with available power at 100%. At about 950rpm the IAC duty goes to 0%, TPS voltage is .82volts with 100% available power. with no change in rpm with IAC duty changing.

It looks like my IAC is bad.

The scanner said TPS voltage at idle should be .90-1.22volts. So it looks like I need to adjust TPS Sensor to get correct voltage?

I just tried to do the IAC valve test on the scanner. I went from 0-100% duty and the rpm did not change at all. Than after a few seconds the scanner said "can not execute test due to PCM hardware or engine component fault".

The connector and wires were in great shape.

I removed the IAC and the value was not resting on the seat. Is this the normal power off position? That would explain my idle raising up some rpm. (the gasket was in great shape/clean/no leaks. I also blew in the IAC hose from the TB and no restriction.

like I said in a past post # 10 ---- guardian mode (4247 rpm showing 89 % power) and rpm exceeded that - overspeed / max rpm exceeded fault set as that was your solid horn after the 2 beeps warning. Good guess on my part

I would reset your throttle plate to the correct position and make sure your throttle cable is adjusted correctly as well. I would rerun the engine making sure idle speed is correct and engine fully warmed up. The I would watch the PWM of the IAC for a fully warmed up engine with correct idle at needs to 26 % theu 35 % PWM best is 30 % spot on at idle.

IMO you need a brand new IAC as well installed.

I just installed a new IAC and ran on the hose. The alarm seems to have stopped and the IAC duty cycle is down around 20% now. It was starting to rain so I had to stop for the night. I will adjust the throttle stop to get 30% at a 650rpm idle.

THANKS for the help John!!!!

I have another question if you don't mind: At a 650rpm idle the timing is showing 0 to negative 9 degrees. Is that correct or do I have something else going on? Knock sensor maybe???

Timing going negative at idle is normal with this application. I've also tried the IAC test with my scan tool with no success. Maybe John can tell us what's going on. Sounds like you have her fixed! Good job. The $$ spent on the scan tool will pay for itself in the long run.

Yes the scanner was definitely a good buy. It gives a lot of good info. I also found out my engine has less hours than the hour meter shows.

I'm thinking the low timing at idle might have something to do with emissions.

On the IAC test there was a slight increase and decrease in rpm, maybe 50rpm if I remember correctly. I'll check again this weekend.

Timing is all over the place at idle normal depending and based how the engine runs and then accelerates. A basic answer here but more info.

Also your scan will show knock sensor faults if they took place plus will show in history of the scan. Knock sensor 1 and 2 fault code(s) number 10 fault code for knock sensor 1 and fault code 11 for knock sensor 2.

Not to get into a full story book of whats going on but a jist of how this ignition works so maybe see whats going on.

The triple nickle as we call it = PCM 555 - it controls ALL ignition events and system operating functions from start up to idling to when the throttle(s) are advancing . It constantly adjusts dwell and spark timing as it uses engine speed and position(s) outputs from the crank sensor and the cam position sensor to control the sequence and dwell and timing of the spark. Do not forget the PCM also monitors other sensors in the system for its information like MAP, ECT, TPS, Knock, MAT, IAC and so on all at the same time and very quickly at that to say the least.

With that said back to the ignition side - PCM 555 has 8 ignition coil drivers or some call them EST outputs (EST = Electronic Spark Timing). They are used to control the ignition driver modules located in each coil themselves. The signals are sent by the PCM to each coil to have the modules open the ground path for the coil primary winding which causes the coil to fire. Anyways basically how it all works in a nut shell.

Great info.

Thanks everyone!!!!!

Ryan I tried the IAC test again today. Going from -100 to +100 the rpm moved maybe 50-75rpm. It was very subtle but you could see it on the scanner display

So what are you adjusting ?