Yamaha YZ250FM 2021 Owner's Service Manual

FUEL INJECTION SYSTEM8-23Fault code No. 21TIP• Make sure that the machine is completely cold before checking the coolant temperature sensor.• Before troubleshooting, disconnect the starter motor lead from the starter relay.1 Mounted condition of throttleposition sensor.Check for looseness or pinch-ing.Check the mounted conditionfor correctness.Improperly mounted sensor Remount or replace the sensor.Refer to “ADJUSTING THETHROTTLE POSITION SEN-SOR” on page 7-8.Start switch to ON (main relayON) and open and close thethrottle several times.Check the condition of the faultcode using the malfunctionmode of the Yamaha diagnostictool.Condition is “Recovered”  Goto item 4 and finish the service.Condition is “Detected”  Go toitem 2.2 Defective throttle position sen-sor.Execute the diagnostic mode.(Code No. 01)When the throttle is fully closed,11–14 displays.When the throttle is fullyopened, 86–92 displays.Incorrect display range Replace the throttle positionsensor.Start switch to ON (main relayON) and open and close thethrottle several times.Check the condition of the faultcode using the malfunctionmode of the Yamaha diagnostictool.Condition is “Recovered”  Goto item 4 and finish the service.Condition is “Detected”  Go toitem 3.3 Faulty ECU. Replace the ECU. Service is finished.4 Delete the fault code. Confirm that the fault code hasa condition of “Recovered”using the Yamaha diagnostictool, and then delete the faultcode.Fault code No. 21Item Coolant temperature sensor: open or short circuit detected.Fail-safe system Able to start engineAble to drive vehicleDiagnostic code No. 06Diagnostic tool display Displays the coolant temperature.Procedure Compare the actually measured coolant temperature with the Yamahadiagnostic tool display value.Item Probable cause of malfunc-tion and check Maintenance job Confirmation of service com-pletion1 Connection of coolant tempera-ture sensor coupler.Check the locking condition ofthe coupler.Disconnect the coupler, andcheck the pins (for bent or bro-ken terminals and locking condi-tion of the pins).Improperly connected  Con-nect the coupler securely, orrepair/replace the wire harness.Start switch to ON (main relayON), and then check the condi-tion of the fault code using themalfunction mode of theYamaha diagnostic tool.Condition is “Recovered”  Goto item 7 and finish the service.Condition is “Detected”  Go toitem 2.Fault code No. 16Item Throttle position sensor: stuck throttle position sensor is detected.