Calling all 496 gurus. alarms after cranking,
 

I have a 496 in my Sonic which alarms 2 beeps per minute only after start up. It does this immediately upon start up. Shows nothing on Rinda scan tool.
The engine starts and runs sounding ok.
I have read in the PCM 555 troubleshooting manual that cam position sensor will only alarm after cranking the engine.
So I have been pursuing the cam sensor, unfortunately that’s not so straight forward with 2003 496 as it require a modification which includes new cam sprocket, timing cover and current sensor to upgrade to current sensor style as the original one is obsolete.
I did try one cam sensor from Summit Racing but I still get the alarm (which also derates power to 90%).
I have also found a direct replacement for my sensor part number from Germany but the engine will not start and just backfires with that in it.
Just wondering if anyone knows are there any other alarms on 496 that will only alarm after cranking the engine? Or any other ideas?
I have also replaced water pressure sensor but would disregard water pressure in any case as it alarms to quickly after starting for it to be that.

We just had one do that last weekend. It was a bad iac. It was actually burned up at the connector.

The 2 beeps should show a code, or at least an error on a scanner, hence why its beeping
Can be several things, see list below


https://cimg7.ibsrv.net/gimg/www.off...d16f78e2cf.jpg

did that give any symptoms? Mine runs perfectly except alarm beeps and power limited to 89%

[QUOTE=AllDodge;4759007]The 2 beeps should show a code, or at least an error on a scanner, hence why its beeping
Can be several things, see list below

Thanks for the info. Re the scanner, definitely no codes other than those which are always on there. I.e. pitot, fuel level, trim etc. I think I have read somewhere that the early PCM555 models didn’t show cam position fault codes, although that maybe a red herring!!!
I will check again through those other sensors on the list. I’m beginning to wonder if it could be ECM issue.

Check voltages, 5V and 12V

You have to know what your looking for on the scanner. The information might be there but you might not seeing it. Look at all sensor values, iac position, voltages etc.

If only they was a 496 guru on the site...... sorry I had to. 😁

5 and 12 volts all good on scan tool

I saw this post by BUP which may explain why I cannot see codes on scan tool.

Merc PCM 555 with software prior to level 091that has a problem and or bad crank & cam position sensor will not set a fault.

With level 091 software if the camshaft position sensor is completely bad or has bad circuit in which causes a signal not to be sent to the PCM, the engine will backfire and not start, if this happens stop cranking and try to start again. keep trying to restart. If the engine does start and two beeps from the audio warning takes place asap it can be more than likely be a bad bad cam PS. It should set a fault code if you can run the motor for 30 seconds straight..

I don't have idle starting issues, backfire or any other give aways. But have decided to order a new 496 cam position sensor update kit. Its a bit of a pain to install because I will have to lift the engine and strip out the front end to replace the cam sprocket and timing cover but I have reached the point of going round in circles. It will take a week or so to arrive from US as I'm in the UK but I will let you all know how I get on.

Any other ideas in the meantime gratefully received.

Agreed with having to know what to look for on scanner. So I can confirm no codes but alarm 2 beeps pm, no voltage issues, any suggestions further to that welcome.

Thanks so far👍

BUP sells direct replacement cam sensors i believe. Save you all the hassle.

Ah that sounds good, How do I get hold of him? I googled earlier but should have guessed to ask here first.

go on Facebook he is on quite of few sites selling his parts,

there many qualified techs out there that can repair your boat, not just one "guru"
what you have there is a simple issue, all you have to do is take to a qualified shop and they will take care of it, I have been in the repair business for a long time, nobody can diagnose your issue correctly over the internet ,its a guess at best, and not every issue requires a ecm overhaul and injectors flushed,,

I would start by having someone that knows what the data readings are and what they indicate and go from there,,if you want to play with it yourself I would stat by checking resistance values on the IAC so you can rule it out.

thanks for that, I am a marine engineer myself, just not a merc gasoline guy. What I did omit to say is that I checked the resistances on the cam sensor and they were out. It’s just been a bit of a mare getting the right cam sensor as there are a few different versions and the version I have is obsolete. I took a gamble on a couple of different ones but neither have been any good.
There is an update kit but everything I order takes a week or 2 to get it in the UK. Not an abundance of 496’s over here either so not many experienced shops.
I will check those IAC resistances too.
more than happy to keep going myself with it, it’s all experience and I’m not looking for one guru, just anyone with helpful information.

all in all I just don’t want to waste 2 weeks waiting for new cam sensor to arrive without checking for other possibilities.

What name does BUP go by on Facebook or other sites?

Google "boats unlimited" for John's contact info

What were the 12V and 5V readings?

Don't know your serial number but if your ready to throw parts at it here is a list

8.1 cam sensors

2001 - Standard PC948, GM 12575182 NLA, Merc 883513 NLA, AC Delco 19338600, Block 1XA, 1XW

2002-2003 - GM 12575183, Standard PC 949, Merc 881666 NLA, Block 2XA, 2XW, 3XA, 3XW

2004+ - GM 12591720, Standard PC260, AC 2133826, Merc 892615002, Block 4XA 0M667238 & up, Block 4XW 0M672041 & up
CDI E13-0004. OEM#: Mercruiser 892615, 892615001, 892615002, Pleasurecraft R020035A
Replaces Part#: Mallory 9-29821 Sierra 18-7646

I know for a fact that John aka BUP works on more 496 s than anyone. They come from all over to get fix. I know from experience and you can go up on FB and ask to see for yourself. here is his website. Call the guy he helps out so many and has fixed stuff that no one else could, www.boatsunlimited.com

thanks for the info

13.1 and 5.00 vdc

I was able to just pick out the part # off old sensor 12575183

serial # M364613

I think 2002 to 2003 engine

If the block code matches then your good