Yamaha Outboard Electronic Throttle (ETV): Checking TPS and APS

You push the lever forward, but the engine hangs just above idle and a warning pops up on the gauge. On engines with an electronic throttle valve, that's a classic sign of a fault in the throttle path: the ECU no longer trusts the signal and limits power. With M-JET DIAGNOSTIC you can read whether the throttle valve, its power supply, the throttle position sensor or the accelerator position sensor logged the fault, and watch the voltages live.

Which engines this applies to

The electronic throttle valve, or ETV, shows up in the fault lists of the F115 to F150, F175 to F250 and F275 to F450 ranges, depending on the ECU. Those engines use two throttle position sensors (TPS1 and TPS2) and two accelerator position sensors (APS1 and APS2) that cross-check each other. The smaller F20 to F100 engines and the HPDI Z series use a throttle cable and a single TPS. On those the app shows TPS voltage and throttle opening angle. You can also tell whether your engine has an ETV by checking whether TPS1, TPS2 and the ETV relay appear in live data.

The fault entries and what they mean

• Throttle valve malfunction: the valve isn't following its target. Check the wiring and connector, the ETV motor resistance and how the valve moves.
• ETV power supply: same steps, plus the ETV relay in live data.
• TPS out of specification: compare sensor 1 and 2 voltages in live data, then check the wiring.
• APS out of specification: same approach, just on the accelerator sensor.

How to read the live data

Put TPS1 and TPS2 side by side, along with throttle opening angle and throttle request in percent. Both sensor voltages should change smoothly at every valve position, with no jumps or dropouts. The same goes for APS1 and APS2 as you move the lever slowly. If one channel tracks cleanly and the other twitches or freezes, the fault is in that sensor or its wiring. Gently wiggle the harness while you watch. If the value jumps right then, you've found the spot. If the entry only shows up after a washdown or in rain, moisture in a connector is more likely than a failed part. Write down the conditions before you clear the memory.

What can be mechanical

Not every throttle fault is electrical. Salt buildup and carbon can make the valve sticky, so the motor can't move it fast enough. In that case cleaning the throttle body per the manual helps more than a new sensor. You measure ETV motor resistance with a multimeter on the unplugged connector. If the connector is corroded, clean it, protect it with a suitable contact grease, clear the fault memory and see whether the entry comes back after a test run.

Related topics

• Yamaha Outboard Idle Learning via App
• Yamaha Outboard Limp Mode: Tracking Down Power Loss and RPM Limiting
• Yamaha Outboard Won't Shift: Remote Control, Shift Sensors and Neutral Detection
• All Yamaha outboard diagnostics topics

Everything runs via app over Bluetooth, for Yamaha outboards with control unit generations from 2003. Learn more about the M-JET DIAGNOSTIC for Yamaha WaveRunner & Outboard.