Help Invent Diagnostic Procedure for Mercury 60-HP with MAP Service Code

[dbtfree15]

[Dear Reader: please help with any suggestions on how to diagnose the cause of a MAP service code on a] Mercury 60-HP BIGFOOT FOURSTROKE engine, serial number 1B004506

After two days of good angling for salmon in the Strait of Juan de Fuca, the Mercury 60-HP BIGFOOT FOURSTROKE engine had another problem: upon turning the ignition key switch to ON from OFF, I heard a dreadful LONG BEEEEEEP followed by BEEP_BEEP_BEEP_BEEP_BEEP_BEEP (six short). On the VesselView instrument a service code for MAP appears. The code says:

401-24
Manifold pressure sensor using time sampling;
input circuit is above the valid limit...
Manifold pressure sensor is not working properly.
Service engine soon.

Fig. 1. Screen capture of MAP service code.

IMG_1812.png (44.12 KiB) Viewed 12434 times

Apparently there are two versions of this code, one for when voltage is too low and one when it is too high. Note: this code was thrown before engine is started, simply by turning on the key.

The engine will start, and it will run for three seconds before stopping. If the throttle is advanced (in neutral gear) and the engine speed increased, the engine will continue to run, but only if the engine speed is kept greater than 1,200-RPM. If the engine speed drops below 1,200-RPM the engine sputters and stops.

Recall that I have already replaced the MAP sensor (in a not-too-long-ago repair). There is a chance [the MAP sensor} is really dead but it seems unlikely.

I now announcing the steps I will perform to diagnose this problem:

Diagnostic process to be tried

1. Turn the key on now that I am back from the saltwater. I sure hope it doesn’t work now that I cut my fishing trip short.
2. Unplug map and try starting to see if there is any change in running behavior.
3. I have the old MAP, and since I know the MAP sensor was not the cause of the last problem with this engine, I will install the original MAP sensor in place of the MAP sensor in there now, and then observe if any change occurs in the engine alarm and running behavior; no change would rule out the MAP sensor as the problem
4. Since I have a spare engine control module (ECM) I may try putting that ECM on the engine and testing for any change. Then if none of those tests led to a remedy, I will continue.
5. Test voltage between leads of the plug-in for the sensor.
6. Test the sensor for continuity where it shouldn’t have it.
7. Identify a way to test voltage with sensor plugged in.

A guy at said it is possible that this could be a caused by low fuel pressure (and a faulty fuel pump). I somehow doubt that. This problem seems very much like it is electrical. I could see the cause of this problem being something totally unrelated to the MAP but being electrical--but the cause is unlikely to be the fuel pump.

[This thread describes further problems with an engine that was previously a topic of discussion in another thread, see

Mercury 60-HP BIGFOOT: Engine Cuts Out Above 3,900-RPM
https://continuouswave.com/forum/viewto ... f=6&t=8072

although reading that thread is not necessary to understand this problem--Moderator]

[jimh]

My suggestion for your diagnosis of this problem: get the factory service manual.

If you have the service manual for the engine, the service manual MAY contain further explanation of the cause of the service code your engine has produced, and may suggest more actions to be taken to identify the cause of the problem and may suggest actions to remedy the problem.

I have to use the subjunctive tense because I do not have access to the service manual for your Mercury engine, but in the service manual of other outboard engines from other manufacturers such as Evinrude, I have seen very detailed information about the correct interpretation of the service code, what components might be involved, and what subsequent behavior the engine will exhibit when this service code exists and is not corrected.

If you are going to undertake the repair and maintenance of these modern engines, you should get the factory service manual. Also, at one time Mercury had a service accessory that would read service codes, but it appears that you already have a device that can do that. That is a good outcome for you, because the older style official service code reader was a dealer-only tool that cost about $1,200. It is nice that you got the service code without spending that sort of money.

[dbtfree15]

Thanks Jim. Yeah the vessel view mobile ($225) does throw the codes but definitely doesn’t have all the info the $1200 device does.

I do have the manual. Unfortunately without the DDY ($1300 tool) instructions are sparse. Attached are images from the manual. For my described state it indicates I should check the resistance on the sensor so that is what I will do… when I find my multimeter, I put it away somewhere new when I moved. :(



Meanwhile I went to go change out the sensor with my old one and the ECM. I was praying oddly enough it would still have the [problem with the engine] this morning (the [problem with the engine] persisted while on the water and after I drove 4 hours home. If I didn’t, then that would make it way harder to diagnose.

Lo and behold, turn the key on and no beeps. Starts right up. Sigh. I am going to exchange those parts out anyway and will test the MAP sensor when I find my multimeter.

Really starting to wonder if I have some sort of deeper electrical defect.

[jimh]

The information you already have is quite useful.

In order to have a good DVM wherever I happen to be, I have to own three FLUKE DVMs. My theory on test gear is if you need to measure some value to see if a device is working properly, you need to have a meter that can reliably and accurately measure that parameter.