Yamaha YZ250FM 2021 Owner's Service Manual

FUEL INJECTION SYSTEM8-242 Connection of wire harnessECU 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 3.3 Wire harness continuity. Open or short circuit  Replacethe wire harness.Between coolant temperaturesensor coupler and ECU cou-pler.green/white–green/whiteblack/blue–black/blueStart 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 4.4 Mounted condition of coolanttemperature sensor.Check for looseness or pinch-ing.Check the mounted position forcorrectness.Improperly mounted sensor Remount or replace the sensor.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 5.5 Defective coolant temperaturesensor.Execute the diagnostic mode.(Code No. 06)When the machine is cold, dis-played temperature is close tothe ambient temperature.Improper display  Replace thecoolant temperature sensor.Refer to “RADIATOR” on page6-2.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 6.6 Faulty ECU. Replace the ECU. Service is finished.7 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.