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Tohatsu 90hp TLDI errors and self-diagnosis functions

C

chartscharts

Member
Howdy!

Yesterday I took my new-to-me 2010 Tohatsu MD90c2 out on the water for the first time.

After engine ran, even in neutral at idle, for a few minutes, it would have all three lights blink on the tach, and RPM wouldn't go above 3000ish. Stopping/starting the engine didn't seem to make a difference.

Service Manual says "TPS does not function" as the problem there, and that it was "self-diagnosable." I tried the reset TPS process on the water, but I'm not 100% sure I got it right. It didn't seem to make any difference.

So, back at home, I ran the self-diagnosis. and the tach read 6600, with the oil light flashing, and the battery light on solid. There wasn't an exact match in the service manual for that code. Closest was tach6000 with those lights which says "#2TPS power voltage low with wiring or component was once broken/malfunctioned."

I pushed the key in again to get the next fault code, and the only thing that changed was the blinking oil light went solid. The closest match was "#2TPS power voltage high with wiring or component was once broken/malfunctioned" which is of course the opposite of the first code.

Pushed the key in again to get the next fault code and it gave me an exact match for "Oil pump malfunction" which didn't make sense to me.

So I wondered if that was fault history. Not sure if I was looking at the current fault or the fault history, I went through the procedure to delete the fault history.

After that, I ran the self-diagnosis again, and this time it said no errors. Huh.

So, I started the engine on the muffs to try to replicate the original problem I had on the water. No luck. Ran great. Let me RPM up to 4000. No flashing lights. Started/stopped several times but never was able to get any lights or problems. At this point, I realized I should have run on the muffs before doing the self-diagnosis to replicate the problem at home before troubleshooting, but I'm a knucklehead.

Anyway, here's my questions:

1. Does the "delete fault history" function actually clear/reset anything? I thought it was just erasing history. Does it actually reset something?

2. Is there any kind of fault that would be consistent with these symptoms and only happen in the water and not on the muffs?

3. Other ideas about what might be happening?

Thanks in advance.
 
Thanks, Paul! So the RPM would have been limited until I deleted the fault history, even if I had fixed the actual problem? Or do the faults go away on their own if you fix the problem? Just trying to make sure I understand how it works.

Do the RPM's match exactly on the codes? Mine was 6600 which didn't exactly match (closest that matched with the code was 6000).

I'm thinking that if there's an actual problem, I ought to be able to replicate it on the muffs. Is that right? Or is there something that could be causing that fault that will only show up next time I launch the boat?

Appreciate your replies and expertise. Thank you!
 
The 3 lights means you need to run diags.
The faults will usually stay logged until you clear them.
Yes, the tach is very precise.
Muffs don't put the motor under load, so it's not really a good test.
 
Ok, thanks. Guess there's not much more for me to do until I can get back down to the ocean, since I haven't been able to replicate the problem on the muffs.

Strange about the TAC reading for those codes. It was clearly 6600, which isn't listed as one of the codes in the service manual.
 
By the way, this is my first outboard boat, and while on the muffs, I noticed it was discharging water from three places....the pee hole on the back (which I expected), but also out of a small hole on the left side down toward the muffs...and lastly in the front of the engine near the transom. What are those other two?
 
Those are drain holes so it doesn't freeze.
6500 and flashing oil is extreme overheat.
6500 and oil ON is regular overheat.
 
I see those codes now. I have a PDF of the service manual, and the rest of the codes were two pages away (designed for facing pages) so I didn't notice them now. Thanks for the clue.

Well, that actually makes perfect sense now that you clued me into the correct code. The water pump was AFU when I got the boat. I replaced that and it's now working great, but I didn't know about those codes, so I didn't clear them before I took it out on the water. So, I bet it extreme-overheated when the pump got broken with the previous owner, and that was the source of that code.

But even though I fixed the water pump, would it stay limited at 3000 RPM and display the three flashing lights during operation until I cleared the code? In other words, it's not enough to fix the problem to return to normal operation, you have to clear the code?

Really appreciate you sharing your knowledge with me. Thanks.
 
Makes sense. When you are cycling through the faults by pushing the key in for 1 second for the beep, how do you know when you are seeing "active' faults, vs. "fault history?" If you had 1-2 active faults and the rest were history, how would you know when you switched from seeing actives to history as you pushed the key in?
 
On the water today. Cleared fault history. After running with no problems for a while the 3 lights started flashing.

Self diagnostic codes were:

  1. Oil on-water off-batt on-800 RPM
  2. Oil flash-water off-batt on-2000 RPM
  3. Oil off-water off-batt on - 5000 RPM
Cleared again and ran a bit more till the three lights flashed. This time it was codes #1 and # 2 but that’s it.

Cleared and just at idle all three flashes and I got code #2. But that’s it.

Cleared and ran but just at slow speed the three lights flashed. I got code #1 and #2 but that’s it.

If I read my codes right, we have for them:

  1. #1 fuel injector malfunction (or maybe wiring.
  2. #2 ignition coil malfunction (or maybe wiring)
  3. CPS malfunction.
It didn't seem like I was limited to 3000 RPM. I could go up to 4000 at near WOT.

What do you make of the changing codes? What would you try next?

Really appreciate any advice.
 
Thanks, Paul. Any problem running my motor up to 3,000 PRM on the muffs for a while to try to replicate the problem? I've heard some say not to run high RPM on the muffs. What's high? And does it matter as long as I'm not overheating?

It takes a few minutes at 3,000 for the codes to show up on the water. Will really slow me down if I have to take it down to the water every time after a I try something to test.

I'll look through my service manual and give those things a try. Appreciate it!
 
A little. Better to get in a test tank... or better yet, on the water. 3000 rpm will splash all the water out of a trash can.
 
By "Test injectors and coils and cps," I think you mean test the resistances on the connectors like the service manual says, right?

Are the cylinders numbered top down? So #1 fuel injector is on top?

All the grounds feel tight and look pristine. I'll try testing the resistances tomorrow.
 
pvanv said:
Test injectors and coils and cps. Verify wiring, esp grounds.
Click to expand...

Ok, Paul (and/or anyone :) ) I'm not sure which one is the #1 fuel injector (are they numbered top down or bottom up?) so I measured all 3.

On all three fuel injectors, I got 1.5 ohms (sometimes 1.6 or 1.7 when I wiggled, but mostly 1.5). The service manual says "1.7-1.9 ohms at 68F." Well it was 83-85 when I measured. So not sure if that means 1.5 is ok or not. Do you?

But the connectors don't all look the same. See picture here: https://ibb.co/nrfL1t4

The #2 ingnition coil (assuming it's the one in the middle) read .6 between the first two posts (manual says .4-.6) and 14 kohms between the third post and the end of the plug cord (manual says 10.8-16.2 khoms). So those all check out just fine.

The CPS measured 531 at 83-85F and the manual says 425-637 at 68F.

What do you think?
 
Well, I disconnected all wiring connectors, cleaned thoroughly, and checked grounds, reconnected, and the errors return.

Not sure what I should do next. The injectors' resistance check reads 1.5 ohms. Service manual says the range is 1.7-1.9. But then again, all 3 injectors read the 1.5 and I'm only getting an error code about #1.

Ignition coil resistance check is within the service manual specs. So, supposedly ok, but still get the error code about the #2 ingition coil after a run.

CPS resistance check is also within the range in the service manual, but still get the error code about it intermittently (not every run).

Looking for advice on what to do next:

Replace #1 fuel injector? Even though it reads 1.5 the same as the others?

Replace all 3 fuel injectors, even though I only get a code about #1, because all three are 1.5 and the range is supposed to be 1.7-1.9?

Replace the injector coil?

Replace the CPS sensor?

Any other ideas?
 
Just realized that I was measuring the injector resistance wrong, and measured it correctly tonight. But it doesn't improve my troubleshooting. All three injectors read 1.9 ohms, which is within the normal range.

So could #1 fuel injector be bad, even if the ohms are in range?
 
Thanks, Paul. Do you know if I have to remove the air rail on my MD90 C2 to replace the fuel injector? Or it seems pretty accessible, I could just swap it out leaving the air rail where it is? Any tricks/gotchas in swapping it out?
 
To pop out the #1 fuel injector (on top in the pic) for replacement, I have removed the little metal plate and connector. Service manual says to twist it a bit to break the O-ring seal, then use flat-head screwdrivers to pop it out. I'll try that. Some questions:

1. Any tricks to that?
2. I assume the alignment is important? Should I mark the orientation before I pop it out? How close does it need to be?
3. I noticed that the #1 and #2 fuel injectors have the connector cable pointing down to the left, whereas the #3 (bottom in the picture) has the connector pointing up to the left instead. Is that normal? I guess I kinda thought they'd all be lined up the same.

IMG-3045.jpg
 
Update:

Replaced all three spark plugs. The old ones didn't look great, not awful, but a bit scorched/dirty.
Replaced the #2 injector coil.
Replaced the #1 fuel injector. The old one did have a bunch of corrosion around the tip (see pic below).

When replacing the #1 fuel injector, when I pulled the old one out, the injector, plus the "fuel injector adapter" (#13 in the service manual snippet below), and the "compression seal" (#12 in the service manual snippet, looks like a black o-ring), all came out with it. But the "fuel injector insert" (#11 in the manual snippet) stayed inside the Air Rail.

Using a small screwdriver as a guide and another to push, I was able to get the compression seal back on the fuel injector insert while still way deep in the air rail. Then I replaced the fuel injector putting the fuel injector adapter in along with it. Seemed to go in fine.

Started up the engine on the muffs, ran great. No flashing lights. But after stopping the engine, I decided to check for codes, even though the lights weren't flashing while it was running. And it gave the code for #1 fuel injector again (but not for ignition coil). Questions:

1. I had thought if it was going to give codes, it would first flash the three lights while the engine was running, to prompt you to go look for codes. Is it normal to give a code when you do the self-diagnostics even if all 3 didn't flash while it was running?

2. Was the injector replacement normal? Was the "fuel injector insert" (#11 in diagram) supposed to come out too?

3. What should I try next? Is it possible I didn't get the fuel injector in right?

Service manual with part #'s:
gXbURhm.jpg

Old Fuel injector:
MbxMy6b.jpg
 
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