Yamaha 2007 XP500 Service Manual page 402

Check for flaws on the teeth surfaces of the front or rear wheel sensor rotors.
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Also, check for any foreign materials. → [D-3, 4]
3. Sensor output has dropped.
Sensor signal output may drop due to failure of the bearings, wheel axle, rear brake caliper bracket
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wheel or sensor housing of (front) the front or rear wheel. Check these components when installed
for looseness, distortion, and bends.
Malfunction code 15 (front wheel sensor) and malfunction code 16 (rear wheel sensor) (No
continuity in the front or rear wheel sensor circuits.)
Broken front or rear wheel sensor circuit is detected.
Front or rear wheel sensor coupler is broken. → [D-3, 4]
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Front or rear wheel sensor or lead is broken. → [D-3, 4]
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Front or rear wheel sensor circuit is broken. → (Refer to "CIRCUIT DIAGRAM".)
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Wire harness (ABS system circuit) is disconnected from the ECU (ABS) coupler terminal. → [D-1]
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NOTE:
Check that both the front and rear wheel sensor couplers are connected securely.
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If the vehicle is ridden after malfunction code 15 (front wheel sensor) or 16 (rear wheel sensor) is dis-
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played, the malfunction code will be overwritten from 15 to 11 (front wheel sensor signal) or from 16
to 12 (rear wheel sensor signal).
Malfunction code 21 (Disconnection and short-circuit of hydraulic unit solenoid.)
1. Hydraulic unit solenoid coupler
Check if the hydraulic unit solenoid coupler terminal is disconnected. (Refer to "ABS CONNECTOR
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LOCATION CHART" on page 8-69.)
2. Hydraulic unit solenoid
Check the front and rear wheel solenoids for continuity → [D-5]
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Check the insulation of all solenoid terminals and the negative battery terminal. → [D-5]
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3. Wire harness (ABS)
Check the hydraulic unit solenoid circuits for continuity. (See the illustration below.)
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1. ECU (ABS)
2. White/Brown
3. Red
4. Red
5. Front solenoid
*Continuity between: "A"–"B", "A"–"C", "D"–"G", "E"–"F"
Check the insulation of the hydraulic unit solenoid circuits and the negative battery terminal.
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4. Battery
Battery terminal is disconnected
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Malfunction code 31 (Disconnection is detected between the fail-safe relay and the hydraulic
unit solenoid.)
NOTE:
Check following the steps in sequence.
1. ABS motor fuse
Check if the ABS motor fuse beside the battery is blown.
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2. Hydraulic unit solenoid coupler
ABS (ANTI-LOCK BRAKE SYSTEM) (XP500A)
8-87
6. Rear solenoid
7. White/Blue
8. Green
9. Fail-safe relay