DTC “c91” (p0500): vehicle speed sensor circuit malfunction

Detected condition and possible cause

Detected condition	Possible cause
Speedometer does not receive signal from the vehicle speed sensor for more than 6 sec. When the motorcycle is running. Ecm does not receive signal from the vehicle speed sensor for more than 6 sec. When the motorcycle is running. Failure in communication between ecm and speedometer with reference to vehicle speed.	Speed sensor circuit open or short. Speed sensor malfunction. Speedometer malfunction. Ecm malfunction.

Wiring diagram

Troubleshooting Caution

when using the multi-circuit tester, do not strongly touch the terminal of the ecm coupler with a needle pointed tester probe to prevent terminal damage.

Note

after repairing the trouble, clear the dtc using sds tool. Refer to “use of sds diagnosis reset procedures” .

Step	Action	Yes	No
1	1 Turn the ignition switch off. 2 Lift and support the fuel tank. Refer to “fuel tank removal and installation” in section 1g . 3 Check the speed sensor coupler (1) for loose or poor contacts.

If ok, remove the speed sensor. Refer to “speed sensor removal and installation” in section 9c .

4. Connect 12 v battery, 10 kΩ resistor and the multi-circuit tester as shown in the figure.

Special tool
(a): 09900–25008 (multi
circuit tester set) Tester knob indication voltage ( )

5. Under this condition, if a suitable screwdriver touching the pick-up surface of the speed sensor is moved, the tester reading voltage changes (0 v → 12 v or 12 v → 0 v). If the tester reading voltage does not change, replace the speedometer sensor with a new one.

Note

while testing, the highest voltage reading should be the same as the battery voltage (12 v).

Is the voltage ok?

• P wire open or shorted to ground.
• Loose or poor contacts on the speed sensor coupler or ecm coupler (terminal “2”).
• If wires and connection are ok, intermittent trouble or faulty ecm.
• Recheck each terminal and wire harness for open circuit and poor connection.
• Replace the ecm with a known good one, and inspect it again.

• Inspect that metal particles or foreign material stuck on the speed sensor and rotor tip.
• If there are no metal particles and foreign material, then replace the speed sensor with a new one.