|
It sounds very strange as the sensor is just a thermistor which is an electrical resistor whose resistance is significantly reduced by heating. As the resistance goes down with heat the voltage that is allowed to pass through the sensor to the ECU/PCM increases. P0118 usually means the ECU has detected a voltage level higher than it should be within design spec. But as you say if this is an air cooled engine, who knows where and what they are using the thermistor sensor connection on the ECU/PCM for.
The joys of EFI and all these sensors is you now have the whole kit as the potential for causing the one problem reading. It could be the sensor itself, it could be the wiring being damaged, open, or having become wet and corroding (if the ECU/PCM is set to throw the error on a no signal/high resistance reading as well as the opposite side of too much voltage), AND it could also be the connectors and connections on the wires and between wires and the sensor and wires and the ECU/PCM, or it could be the ECU/PCM module itself and finally it could be what the sensor was set up on the bike to monitor in the first place is actually malfunctioning or allowing so much heat through its triggering the ECU/PCM error code. So now you have to add in addition to all of the above a complete sleuthing as to what and why they would use that sensor connector on the ECU/PCM in your scooter, for this my best guess would be a engine temperature reading off of the top end of the motor rather than the IAF sensor as air intake is P0113 code. It makes more deductive sense to me as the scooter engines are usually housed away from direct air cooling by being hidden away in a housing. So there is another thing to check, are the air intakes that direct outside air to the engine blocked or restricted in the air flow now compared to when it was new?
Keep in mind I don't even know what your scooter looks like or how its designed, so you'll have to go over it and do the troubleshooting but the above information should give you enough of a decent war chest of what to look for. A simple DMM test on the sensor signal wire to the ECU/PCM can help as well. If its no voltage then its a broken wire or connector connection or the sensor is shot. If it has a voltage and you look up the sensor data sheet and find that the voltage you measured and wrote down is too high for normal designed output and the engine isn't even on or running and is cold then the sensor is shot and should be replaced. etc. etc. etc.
Now you know why some folks just go with carburetor. EFI buys you great cold start and off to the races starts in the morning and that is about it. When things go bad it becomes a much larger rats nest to diagnose the error codes and figure out what has really gone wrong as you are now troubleshooting the entire electronics and sensor and wiring and connector package in addition to all the mechanical engine parts as well.
|