Suzuki GSX-R 1000 Service Manual: DTC “c91” (p0500): vehicle speed sensor circuit malfunction

Detected condition

Possible cause

• Speed sensor circuit open or short.
•  Speed sensor malfunction.
•  Speedometer malfunction.
•  Ecm malfunction.

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.

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.

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.