Yamaha YBR 125 workshop manuals on Ebay UK
Yamaha YBR 125 Throttle position / intake air temp and pressure sensors
all three of these functions are read by the same throttle body unit .
throttle body assembly 5 pin connector
connectors left to right as photoed
V T G M A
these are so easy to test with the FI diagnostics tester , bit more complicated without so here goes .
For more detailed explanation try the Haynes workshop manual as im doing this from memory
Safety Message: Before testing electrical components, ensure the ignition is off and the battery is in good condition. Use a high-quality digital multimeter and avoid piercing wires, as this can lead to corrosion and future electrical failure.
Yamaha YBR 125 Sensor Diagnostics (TPS, Air Temp & Pressure)
The Yamaha YBR 125 Throttle Body Sensors post details how the three primary fuel-injection sensors are integrated into a single 5-pin unit.
1. Intake Air Pressure Sensor (MAP)
Fault Code 13/14: Indicates wiring issues, a blocked sensor port, or sensor failure.
Voltage Test: With ignition ON, check the Pink/White (+) and Black/Blue (-) wires. Correct voltage is 3.75 to 4.25 volts.
Maintenance: Ensure the air passage to the sensor is clear of debris or carbon buildup.
2. Intake Air Temperature Sensor (IAT)
Resistance Test: Measure across the Brown/White (+) and Black/Blue (-) wires using the K-ohms scale.
Expected Values:
2007–2009 models: 2.4 ~ 2.9 K-ohms.
2010 onwards: 5.7 ~ 6.4 K-ohms.
3. Throttle Position Sensor (TPS)
Input Voltage: Check the Blue wire; it should show a steady 5 volts.
Output Voltage Range: Measure between the Yellow/Blue (+) and Black/Blue (-) wires.
Throttle Closed: 0.63 ~ 0.73 volts.
Throttle Open: Voltage should increase smoothly as the throttle is opened.
Intake air pressure sensor
Fault code 13 faulty wiring , damaged sensor , faulty ecuThis is a part of the above sensor , first check all wiring , turn on igniton and then test voltage at the
+ positive Pink / white wire , - negative black / blue wire . The voltage should be between 3.75 and 4.25 volts . if this is not correct change the sensor , if still not rectified try replacement ecu .
Intake air pressure sensor
Fault code 14 blockage or ecu failureclean out the hole to the sensor to make sure air flows as it should or replace sensor , or replace ecu if this fails .
Intake Air temperature sensor
Check all wiring to the sensor is always a good start , clean out with contact cleaner
and retry .
Using K-ohms scale , + probe to brown/white wire , neg probe to the black / blue and test resistance measurement.
should be values of 2007-09 models 2.4 ~ 2.9 K-ohms
and 2010 on 5.7~6.4 K-ohms .
TPS throttle position sensor
Check all wiring fist and clean conectors , it does work , sometimes .
Set multimeter to volts , + positive probe to blue wire , voltage should be 5 volts .
to check the output voltage range , + positive to Yellow/blue wire , - negative to Black/blue wire voltage closed should be 0.63~0.73 volts , and should increase in voltage as throttle is slowly opened to fully open position .
see more Yamaha YBR 125 blog posts
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