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Mercruiser Fault Codes??

Old 05-10-2014, 06:38 AM
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Default Mercruiser Fault Codes??

Seems like fault codes are a black box? Well guess they really are! and I'm having trouble determining if some or all of these really apply. I have twin 8.1 L Mercs and the codes I get don't seem to make sense unless the ECMT is failing and throwing bad codes? Any thoughts....Faults shown are:
94 Pitot Pressure Circuit Low
75 Fuel Level 1 Circuit High
118 Steering Position circuit high
191 Fuel level 2 circuit high
179 Starboard ECMT Overheat..

any comments appreciated!
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Old 05-10-2014, 09:31 AM
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All of those codes look normal except for the last one. Not sure what that is.
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Old 05-10-2014, 11:48 AM
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Yes and no about normal codes. Depending on your 8.1 app. Do you have smartcraft gauges - do have DTS - do have a catalyst 496 . Would need to know serial numbers of your motors to determine what you have as far as the 8.1. I will say this again and again anytime you take your boat in for service or buy parts from a OEM dealer the first thing they need to know is what is the serial # of the engines. Why because a 2001 496 is totally different set up than a 2010 496. Serial number breaks determine as were parts have change and different setups of that same engine. This holds true for all marine engines.

With that said I can not speak 100 % if your codes are normal or not for the first 4 codes not knowing exactly how your 496's are set up exactly from the factory or boatbuilder. Anyways most of the times on a standard 496 especially the earlier models without DTS (digital throttle & shift) these codes are meaning less.

CODE 179 Starboard EMCT - is Starboard exhaust manifold temperature HIGH. Could be sensor or a cooling problem.

I am marine factory OEM trained now for 25 years. Just in case any needs to know where my logic comes from.



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Last edited by BUP; 05-10-2014 at 12:01 PM.
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Old 05-10-2014, 12:35 PM
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BUP, I have a question if you don't mind. Have twin 2003 6.2 mX's with SmartCraft.. Ran flawlessly up to 200hrs,,got around 240hrs now with an annoying warning 'overspeed throttle back' massage on the port engine only.Water pressure, water temp, oil pressure all indicate identical on both SmartCraft gauges Tried swapping the ECM 555's and the problem stays with the port engine.Have the cool fuel system. I removed the small s/s filter already in the regulator because it seemed to be clogged up and raised fuel pressure close to 70 on the Schrader valve.Fuel pressure is fine now but still get the warning intermittently.Swapped the water pressure sensors on the PS coolers,,didn't make a difference.Last thing I have yet to try is swapping the oil pressure sensors [ not the sending unit since it sends the right readings to the SmartCraft gauge and the backup gauges I have for all functions] and see if that causing the problem. Oh,,and tried swapping the drive lube monitor bottles too thinking the float inside may have got stock on the bottom sending false low lubricant level.
I have the Rinda scanner and it records the same message of overspeed. Thanks

Last edited by spectras only; 05-10-2014 at 12:38 PM.
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Old 05-10-2014, 01:13 PM
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R U saying just an Overspeed code ? the jist

your recommended rpm range is above what is recommended for your app
are you getting a beep beep or a warning horn ?
If so here some added info after beep or horn.

Cylinders stop firing next typically will have a fault set of overspeed 1 (meaning level 1 overspeed) in which will or can cause the power to be limited but especially will reduce power if you reach level 2 - Overspeed 2 code.. Guardian mode

some causes of these overspeed codes / faults,

too high rpms
too much trim
too much prop vent
prop hub slippling / cracked hub / or if rubber hub - worn - slipping
engine coupler slip / worn
also too much throttle reving in neutral
also too much throttle by far when running on the water hose / unloaded - whether in neutral or in gear

HOPE THIS HELPS Have to run for the day. Good luck

Last edited by BUP; 05-10-2014 at 01:18 PM.
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Old 05-10-2014, 01:35 PM
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Bup, the rev limiter in the ECM is set at 5150. My WOT is dead on 5000rpm with Bravo1 26P props.This problem came out of the blue two years ago while cruising around 4000.No prop slip [solid hub] over revving or coupler problems. I can stay on the sticks WOT for a minute or two before the warning comes on.If I stay below 42-4300 I can cruise all day long.Pretty much do everything on my boat, can lift the engines out in a jiffy to do service but this just stumped me. May have to drag it down to my friend's shop, he has the complete Mercruiser diagnostic equipment that tells more than the Rinda scanner.I think one of the 64 monitoring functions in the ECM555 did me in,LOL Thanks for the quick reply.

Last edited by spectras only; 05-10-2014 at 01:38 PM.
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Old 05-10-2014, 03:24 PM
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Default Thanks for your help!

Just a quick thank you to all who responded, you all have a wealth of experience and your willingness to share is awesome.....I do the same in areas I know well...but this isn't one of them so really appreciate your input!
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Old 05-10-2014, 07:24 PM
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Sounds like BUP knows what he is talking about.

These are the codes that always showed up on my 496HO, no smartcraft, no DTS, 2005 model.

3. TROUBLE CODE STATUS

Current ECM Codes

Sensor Fault, click Read Fault button for details

Trouble Code List:
PITOT CKT LO Code is active
FUEL LVL CKT HI Code is active
STEER CKT HI Code is active
TRIM CKT LO Code is active
FUEL LVL2 CKT H Code is active
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Old 05-11-2014, 10:43 PM
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as far as these faults always showing up, here is why, fuel lvl2 ckt h in which means if you had 2 gas tanks then you have a real active code for some reason.

Since you do not have a second gas tank nor the sensor nor a connected harness for it, the ecm will record and store these codes by default. These faults can be totally ignored if these sensors are not installed and or a connected harness to that app.

All DTS apps will have steering angles (STEER CKT HI) without DTS this code is defaulted by the ECM so it will show up. Again if you do not have DTS then there is no connection nor a sensor for STEER CKT HI.

Anyways just making a point to as why you see these faults for a lot MPI engines with PCM / ECM 555. Anyways not to go into great details about it - I hope this helps.

Last edited by BUP; 05-11-2014 at 11:03 PM.
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Old 05-11-2014, 11:09 PM
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SO if I remember correctly a MCM 6.2 MX in which MCM models are sterndrives the rpm range is 4800 to 5200 at full throttle.

The MIE 6.2 for inboards that would be MX 6.2 inboard and the MX 6.2 Horizon inboard models the rpm range is 4600 to 5000. Anyways I would swap your smartcraft gauges or the connections (if possible) and see if the overspeed message follows.

Last edited by BUP; 05-11-2014 at 11:17 PM.
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