What I learned about "Check Engine" and Engine Codes

[wahoo33417]

Maybe others knew this, I didn't. ECU's store engine codes and continue to send them to the gauge even if the problem no longer persists.

On the second day out of a planned three week boating trip in Canada, Yamaha square gauge began scrolling "Check Engine" message. By holding Mode button for ten seconds the gauge shows engine code 72 which translates to cam position sensor. But the (starboard) engine is running great.

I'm in a fairly remote portion of Canada, so I continue on to my destination, Bruce Mines, in the North Channel.

Same occurs the next day, except now I'm in a marina with a Yamaha dealership. The dealership says it would take 2-3 weeks to get in sensors for my 'old' engine. So he calls in his tech, who says these sensors are so touchy, there are many things that will cause them to send a false signal to Electronic Control Unit (ECU). If your engine is running well, I wouldn't worry about it.

So I try not to.

By day five of seeing and clearing this code on my square gauge every day, I call the Yamaha tech at my Grady dealer. She says virtually the same thing.

The engine loves the cold(er) water and runs great the entire trip. But still sends that code to the gauge every day.

At home, the Yamaha tech says there is one short blip stored in the ECU near the beginning of the trip. No other signals from the sensor after that.

What happens is that, until that short blip is cleared from the ECU, the ECU re-sends that 72 code to the gauge at some point upon each new start up. Every time I looked at that 72 code on the gauge, it cleared itself, whether I meant to or not. I know, because when I would turn the engine off for the day, but leave the key in the 'on' position, the code was gone from the gauge.

But, of course, it wasn't gone from the ECU.

The dealer said the most common cause for these sensors to send a false signal is a voltage fluctuation. Either from bad batteries or cable or charging system. All that checked out.

Then they swapped sensors and ran the engines hard. Of course, I had already put over 100 hours on the engines since that 'blip' recorded by the ECU. But the dealer couldn't get the signal to repeat and concluded the sensors are fine.

So why did one of them send that 'blip'? Just one of those things is the technical answer.

 

[seasick]

Since the code cleared after the sensors were swapped I would assume that the act of removing and reinstalling the 'bad' sensor cleared up the initial fault. Sounds good but I am not a believer in 'the error just went away:
The proper procedure would have been to replace the sensor but I understand the issue of available replacements. . It is possible that the removal and swapping fixed an issue like a bad connection

On modern ECUs errors are stored in memory and stays there until cleared by a tech using the diagnostic service tool. The alarm itself may be active meaning that it is currently occurring or it maybe fault history. I would assume that if it weren't currently active, it would not be posted every time you start the motor. Since you did see it every day, it seems like something in the cam sensor logic failed during initial self test.
There is some validity to the voltage variation theory . Many modern sensors are powered by a regulated power supply. like a 5 volt reference source. If it is out of kilter, alarms may be generated for devices that really aren't bad. I don't know how common these false errors are on Yamis due to low voltages, but they are common on some Mercs .

A bad cam shaft sensor could cause, hard starts, rough idle, rough performance at speed, excessive fuel burn, detonation, excessive carbon buildup and probably a few symptoms I missed
So keep an eye and an ear on the motor for any oddities. Keep an eye on BOTH motors in case the sensor was bad.

 

[seasick]

I decided to do some research and what did I find
You already posted your question on THT and got a lot of responses.
Was this post a check on Great Grady information?
I don't know but I did learn about one symptom being a high idle.
I also said hmmm when I read the post about battery cable replacement but how that works with twin motors is unclear to me,

 

[wahoo33417]

Seasick: Thanks for investigating, but not me posting on THT. But I will look for that - thanks.

To be clear, I would clear the warning from the gauge once each day while I was running. It would never pop up again that same day. But it would always come back, only once, the next day.

I know (believe) I understand that once that one event is stored in the ECU, it will be sent to the gauge each time the engine is run again. The weird thing is, it might take 20 minutes or an hour to get the "Check Engine" message on a given day.

I thought I was getting a new, fresh warning every day. I wasn't. I was being resent that same 'blip' that registered in the ECU on the second day.

Seasick you are also correct in that these sensors are apparently in short supply nationwide. I'm told it will take about three weeks to get them in.

I also agree with you that even a blip happened for a reason. I suspect that if they the dealer had these sensors on hand, I would have been told they needed to be changed.

When they are on hand, I'll get them changed when it coincides with something else that needs doing. My dealer charges $300 just to pick the boat up and drop it off at the ramp 1 block from the dealership. Sometimes I can talk them out of this. They are expensive enough as it is. For some reason, that fee just irks me.

 

[seasick]

My bad...Sorry for jumping to the conclusion that you poster on THT.
I think this is the post I thought was the same boat

https://www.thehulltruth.com/boating-forum/1035941-yamaha-f250-code-072-a-printerfriendly.html

 

[wahoo33417]

Seasick: Thanks. I read through the link on THT. I guess I'm fortunate that my engine never skipped a beat. Especially where I was.

I won't order a new $300 sensor just yet. All my fishing and snorkeling is within 10-12 miles of the inlet. Not far to get home on one engine. And I always have TowBoatUS.

If engine continues to run well, I'll have to make a decision for next summer's far-away boat trip!

If code pops up between now and then, then the decision is made for me.

Tx, Rob

 

[DennisG01]

It's not all that uncommon to see issues like this - a sporadic/erroneous code. Everythign now-a-days is so voltage sensitive (sometimes to a fault) that it just takes one little dip of V to set things off. Flaky connections... dirty connections... etc, etc, etc. All of this plays a role into creating hard-to-find issues - and when these issues are sporadic, it often becomes nearly impossible to find until the issue starts happening more often.

For now, your plan is the best... keep boating as-is

 

[seasick]

Seasick: Thanks. I read through the link on THT. I guess I'm fortunate that my engine never skipped a beat. Especially where I was.

I won't order a new $300 sensor just yet. All my fishing and snorkeling is within 10-12 miles of the inlet. Not far to get home on one engine. And I always have TowBoatUS.

If engine continues to run well, I'll have to make a decision for next summer's far-away boat trip!

If code pops up between now and then, then the decision is made for me.

Tx, Rob

I would do the same as you plan to do.
There are videos on testing cam position sensor, mostly for cars but there is probably something out there.
I assume that the mechanic left the sensors swapped so keep an eye out for oddities on either motor and if you get an alar, whether it followed the motor or followed the sensor will be a big help.
I had one additional thought pertaining to the voltage discussion. It is possible that you have a somewhat excessive voltage drop when the motor is first cold started. That could result in a low voltage condition at the engine and cause a sensor alarm. Once the motor is running and the battery has been charged a bit, the sensor may not be be so picky. These things can be tricky to track down but during next season prep of it the alarm pops up on the same motor, I would take a good look at the battery condition (load test) and check / clean all battery cable connections including the pos and neg motor feeds.
Good luch

 

[wahoo33417]

Thanks, Seasick. I did have the dealer do a load test of the batteries before this trip. Along with many other things, like fuel tank pressure test, replace under-deck drain hoses and full service on engines.

I knew I was going into a somewhat remote area with no Sea Tow or TowBoatUS.

My three group 27 AGM batteries are nearing five years old now. So another load test will be in order before next summer's long-distance trip.