Schematic for F90TLR

[jackmanjls]

Would this be a correct approach to troubleshoot.

From the manual: Sensor assembly(intake air temperature and intake air pressure)

For the other sensors...with the meter on the 5v ref and the engine running start disconnecting sensors until the 5v ref goes back to 5v. Remember when the engine runs the 5v goes to 3v.

Is this a good approach?

[rodbolt17]

that approach will work.

[jackmanjls]

When I look at the wiring diagram and follow the orange wires I see the output of the ECU to connector L. Thei L connector has 2 output wires one goes to the TPS and the other goes to the Sensor Assembly.

I take this info and go to the motor. I monitor the 5v ref (pin 20) at the ECU. I start the motor and the ref goes down to 2.85v (before it was 3.0v).

I stop the motor and disconnect the TPS, start the motor and still get 2.85v.

I stop the motor, connect the TPS and disconnect the Sensor Assemble, start the motor and still get 2.85v.

Then I disconnect both TPS and Sensor Assembly and try to start, it doesn't start but the meter still indicates 2.85v.

To bird dog this even further I go back to my last known YDS diagnostic:

Diagnosis Record
Total hours of operation 1038
Code Item Occurred
37 Intake air passage 725.8
18 Throttle position sensor 756.2
23 Intake temp sensor 756.2
28 Shift position switch 756.2
29 Intake press sensor 756.2

Notice that the Intake air and temp sensors have a fault. These 2 combined are the Sensor Assembly that uses the 5v ref.

I go to the manual and find the following:

23 - Incorrect sensor assembly (intake air temperature) signal

37 - Incorrect idle speed control signal

Comment: The motor has 1000+hrs and ran fine to this point. Notice that the errors occured at 725 and 750 hrs. I had over 250hrs of smooth operating.

Keep in mind that this is a new ISC valve.

Any ideas on what this is telling me?

[fairdeal]

ideas?
something is loading down the 5V circuit.
many sensors are on that 5v ref.
I have seen water pressure sensors and speed sensors do it.
the 5V is generated from the ECU and fed all over. look for a load or a corroded connection.

"unless I am mistaken" there are only four possible "sensors" (4 "orange wire users") on that engine:
- TPS
- MAP/temp (a dual sensor)
- Command Link "S" (speed)
- Command Link "W" (water pressure)

The ISC valve has no sensor/no possible effect on the reference voltage.

Is there a Command Link water pressure/speed sensor installed? poster child for shorted reference voltage....

[pstephens46]

I'm confused.

[99yam40]

I'm confused.

is that odd or different than normal?

[jackmanjls]

Fairdeal...your comment,

Is there a Command Link water pressure/speed sensor installed? poster child for shorted reference voltage....

No water pressure or speed sensor that I know of.

================================================== ==========================================

Unless I'm looking at the wrong wiring diagram there are only 3 orange wires. One is the output from ECU and the other 2 go to the Sensor Assembly and TPS.

So far the manual has been fairly accurate.

Interesting thought about the Command Link. I have the square version. Is there an orange 5v ref of is it some other color?

As a first step...is there anything you can suggest where I can completely disconnect the command link to see if that is the issue?

[boscoe99]

I'm confused.

Yes, less than normal confusion or more than normal confusion?

[pstephens46]

"unless I am mistaken" there are only four possible "sensors" (4 "orange wire users") on that engine:
- TPS
- MAP/temp (a dual sensor)
- Command Link "S" (speed)
- Command Link "W" (water pressure)

The TPS has no sensor/no possible effect on the reference voltage.

Is there a Command Link water pressure/speed sensor installed? poster child for shorted reference voltage....

TPS sensor or not?
Part of the 5vt daisy chain or not?

I'm going to go play with my Seastar.

[fairdeal]

TPS sensor or not?
Part of the 5vt daisy chain or not?

.

My apologies - and thank you for pointing out my error.

I meant to write that the ISC valve has no sensor and can not effect the 5v.

Of course the TPS is part of the 5V system

[boscoe99]

Fairdeal...your comment,

Is there a Command Link water pressure/speed sensor installed? poster child for shorted reference voltage....

No water pressure or speed sensor that I know of.

================================================== ==========================================

Unless I'm looking at the wrong wiring diagram there are only 3 orange wires. One is the output from ECU and the other 2 go to the Sensor Assembly and TPS.

So far the manual has been fairly accurate.

Interesting thought about the Command Link. I have the square version. Is there an orange 5v ref of is it some other color?

As a first step...is there anything you can suggest where I can completely disconnect the command link to see if that is the issue?

The manual is hosed. Typical Yamaha garbage. But it is all that is available.

Beginning in 2006 Yamaha four stroke EFI models were provided with the ability for two optional sensors to be installed. Sensors are one and the same but used in two locations for different purposes. One is referred to as a Speed sensor and the other is referred to as a Water pressure sensor.

Early sensors were known to have a problem whereby water would get from the wet side to the electrical dry side. Water might migrate up a wire all the way to the ECU or to other places. Check your motor to see if the optional sensors have been installed. Either one or both. The connector to the water pressure sensor will be marked with a W. The connector to the speed sensor will be marked with a S.

The SM does not depict the wiring for these sensors. Each will be connected with a three wire connector. One of the wires is Orange. For the 5 volt supply.

[fairdeal]

Unless I'm looking at the wrong wiring diagram there are only 3 orange wires. One is the output from ECU and the other 2 go to the Sensor Assembly and TPS.

So far the manual has been fairly accurate.

Interesting thought about the Command Link. I have the square version. Is there an orange 5v ref of is it some other color?

As a first step...is there anything you can suggest where I can completely disconnect the command link to see if that is the issue?

I have several times been disappointed in finding the Command Link wiring reflected in a Yamaha Service manual...

I will check tomorrow in daylight the wire colors on my 2006 F90 "S" and "W" connectors.

But you can easily see if either of yours is connected to a sensor, or just parked/plugged.
If one or the other is, just disconnect it - no need to disconnect the CL itself.

[boscoe99]

[jackmanjls]

I have several times been disappointed in finding the Command Link wiring reflected in a Yamaha Service manual...

I will check tomorrow in daylight the wire colors on my 2006 F90 "S" and "W" connectors.

But you can easily see if either of yours is connected to a sensor, or just parked/plugged.
If one or the other is, just disconnect it - no need to disconnect the CL itself.

I check and recheck the wiring diagram and I don't have a "W" connector but I do have an "S".

The "S" connector is part of the lower ECU connector, pins 19 - 52. Pin 20 is the orange wire but that goes up to connector L on pin 13.

In addition just below the wiring diagram is an index of references for the wiring diagram and in that list there's nothing about speed or water pressure sensor.

Could it be that the CL is an add on and not included in the wiring diagram?

[fairdeal]

as Boscoe has explained, your SM does/may not show the Command Link wiring - but its there.

Here are the "S" and "W" connectors as they come from the factory - not connected to a sensor: