From the VX1100 of 2005 onwards, every Yamaha four-stroke in the app has an electronic throttle: the VX1100, VXR and VXS, the 1.8-litre FX HO, the FZ and SVHO models, the GP1800, the newer VX, the EX, the SuperJet, the JetBlaster and the 1.9-litre machines. The older FX140, FX1000 and FX1100 are different and have no electronic throttle. The three abbreviations on the fault list look cryptic, but the system is simple once you know what each one does.
Three parts, three jobs
The APS (accelerator position sensor) sits on the lever side and tells the control unit how far you are pulling. The TPS (throttle position sensor) sits at the throttle body and reports how far the valve is actually open. The ETV is the electric motor that moves the valve. The control unit reads the lever, decides what it wants, drives the ETV and then checks the result with the TPS. If the valve is not where it should be, you get a fault.
Both the throttle sensor and the lever sensor are doubled. The app shows TPS1 and TPS2 and APS1 and APS2. The two signals of each pair are meant to track each other, which gives the control unit a way to catch a sensor that has gone wrong. That is also the best tool you have: when you watch the live values, a pair that agrees is healthy, and a pair that drifts apart is not.
Code ranges, with a caveat
For the newer control unit generation, the drive faults of the ETV sit roughly in the range 112 to 145, TPS faults at about 124 to 128 and APS faults at 131 to 135. These ranges overlap in some lists, and numbering differs between sources and between control unit generations, so I would not rely on a number alone. The text the app gives with the code, and its suggested checks, are the better guide. The older GP1300R uses a different numbering, with the throttle sensor reported as code 24 in its generation.
Reading the values
Open the live data and move the lever slowly through its whole travel. The APS pair should climb smoothly, without steps or dropouts. Any jump while you move steadily, or a value that disappears and comes back, means the contact in that sensor or its plug is poor. The same applies to the TPS pair once the engine is running and the valve follows the lever. A value that jumps while the real part is standing still is usually a contact problem and not a dead sensor, so unplug and inspect the connector before you buy anything.
From about 2012, and on all the TR-1 engines, there is also an accelerator idle switch, which has its own code (51). It tells the control unit when the lever is fully released.
When the electronics say everything is fine
If the pairs track each other and no code is stored, the throttle is probably not the cause of a power problem. A sluggish ski with healthy throttle values points toward the intake, the pump or the engine itself.
The Yamaha version of the M-JET Diagnostic reads all four throttle signals live on the supported electronic throttle models. Throttle valve faults (ETV, TPS, APS) covers the typical fault patterns, and after a repair or a battery change the throttle learning may be needed.
