555 ECM faults

[how much]

I have a 2005 5.0L MPI s/n OW327906 with Alpha One drive. I have a Rinda scanner and am getting some codes I don't fully understand. Furthermore the engine will crank and fire off - but only for a moment it never really starts and idles. I have good fuel pressure. The tone beeps twice with the key on but I don't think any of these faults are the reason for the no start. The faults I am seeing are 27 BLK PSI CKT LO, 94 Pitot CKT LO, 75 Fuel LVL CKT HI, and 130 Trim CKT HI. The ECM 555 Diagnostic manual doesn't refer to any numbered fault codes that I found, so does Rinda assign the numbers themselves or what? Thanks, Scott

 

[Don S]

Re: 555 ECM faults

Rinda tools does nothing more than read the codes put into it by the ECM's
Owning the scan tool, owning a manual, and not understanding the system and following all the steps will leave you frustrated. But just looking at the codes you listed, I would bet money those items aren't even hooked up and have nothing to do with your problem as you mentioned.

Do you have spark? Do you have fuel? Do you have compression? That's where you start.

 

[Anchor Management 1]

Re: 555 ECM faults

If you start the engine and hold the ign. key in the start position will it keep running?

 

[Fun Times]

Re: 555 ECM faults

The codes you show are normal and not hooked up to any thing, So that is ok. what is your fuel [PSI} going up to at key up and while trying to start. Hook up a timing light to see if you are getting a lot of spark while cranking off the coil wire then move it to a few plug wires to see if you get spark when the rotor comes around to that wire at a even flow. Have you tryd to move the throttle up while cranking? Also try wiggling the main wire harness from the boat that plugs in to the engine. It is a bigger round rubber black plug it might have a hose clamp on it some times. Also dose your tack [RPM] gauge move up to around 400rpms while cranking?

 

[45Auto]

Re: 555 ECM faults

Do you have Mercruiser Manual #36, ECM 555 Diagnostics? I didn't see it under the Adults Only sticky, but I downloaded it from somewhere. If you have it, follow the troubleshooting procedure starting on 2A-12. If you don't have it, let me know and I'll see if I can get it posted somewhere.

 

[how much]

Re: 555 ECM faults

My compressions range from 150 to 160 psi and the spark tester shows good spark from the coil. The fuel pressure is 40 psi with key on engine off. What I found this morning is the fuel quality is suspect. I found about a quart of water and some unidentified "red-ish" fluid after taking a 1.5 gallon sample. So now I am off to get more gas and do some flushing. I will continue to update. Thanks, Scott

 

[Don S]

Re: 555 ECM faults

Do you have Mercruiser Manual #36, ECM 555 Diagnostics? I didn't see it under the Adults Only sticky, but I downloaded it from somewhere. If you have it, follow the troubleshooting procedure starting on 2A-12. If you don't have it, let me know and I'll see if I can get it posted somewhere.

#36 is in the Adults Only sticky, it's the very last one.

 

[JustJason]

Re: 555 ECM faults

If your getting spark, and your getting fuel, then the fuel/air ratio is off or the spark is happening at the wrong time. I'd be looking at the TPS or IAC first. If you found water in your fuel then that definitely needs to be addressed, but I don't believe that's the source of the problem.

 

[how much]

Re: 555 ECM faults

I got the water out of the fuel but still no start. I kept looking at the MAPT sensor and was seeing a temp of 248 F and if unplugged 32 F. The wiring was good but I knew the sensor would need replaced on Monday. What I didn't notice was the MAP side of it. It also is bad but the ECM is not faulting it. The MAPT is not shorted or open it's like the calibration is shifted from normal. So anyway with the MAPT unplugged the engine fires right up and idles smoothly. Thanks, Scott

 

[JustJason]

Re: 555 ECM faults

You sure you know what your looking at? First, there's no such thing as a MAPT sensor. There's a MAP sensor, and that should be reading 14.6psi KOEO. Nothing to do with degrees. Are you sure your not confusing your ECT with something else. A dead map will cause a no start.

 

[Fun Times]

Re: 555 ECM faults

Can you take a photo of the sensor and post it? We might be able to help some.

 

[JustJason]

Re: 555 ECM faults

Or better yet take a photo of the display screen on the techmate.

 

[how much]

Re: 555 ECM faults

MAPT = manifold absolute pressure temperature sensor. The two signals are combined as one unit. It is mounted on the top of the intake towards the rear. It measures the intake pressure (vacuum) and air temperature so the ECM can calculate the air density/engine load for proper fuel scheduling. It is different than the ECT. Hopefully the pics I attached come through. Thanks, Scott

 

[how much]

Re: 555 ECM faults

I see the pictures are poor and I tried to show a page from the repair manual but it is hard to read. If you download the ECM 555 Diagnostic Manual the MAPT description is on page 3A-26. Thanks, Scott

 

[how much]

Re: 555 ECM faults

Here are the MAPT (temp side of sensor) scanner screen shots. The 260 F is with sensor connected and the 32 F is disconnected. Thanks, Scott

 

[Don S]

Re: 555 ECM faults

I don't see what the problem is, you know it's bad, replace it and retest.

I especially like the discription in the 36 manual about the MAP/T sensor
Note the underlined parts about the location of the sensor. Makes it sound like it's in two places at one time.

Also look in the blue box about the MAP portion of the sensor. From what I read there, it may or may not set a code.

 

[Fun Times]

Re: 555 ECM faults

Wow I learn something new every day I never noticed the map/t sensor before thanks for showing me that. Normal their is too different sensors to read the MAP, And the other one would have been a sensor that would look like a engine coolent temp sendor. Well good job on finding that are you going to order a new one and try it out? It sounds like you found it, the reading of 260 is way to hi normaly that would read about the air temp out side if the engine was not running for a long time and would avarage around 110-140 in temp with engine on, And helps aujust the fuel curve a little in hot or cold air temps.

 

[JustJason]

Re: 555 ECM faults

I didn't know that either. I apologize for my previous bad advice. I to learned sumptin new today

 

[how much]

Re: 555 ECM faults

New MAPT sensor fixes the starting problem. Local dealer $240 + tax, online $188. I waited for it in the mail to save $40+.

Thanks,
Scott