Suzuki GSX-R 1000 Service Manual: DTC “c28” (p1655): secondary throttle valve actuator (stva) malfunction

Detected condition

Possible cause

Ecm does not receive communication signal from the stva. Stva can not operate properly or its motor locked

• Stva malfunction.
•  Stva circuit open or short.
•  Stva motor 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. Lift and support the fuel tank. Refer to “fuel tank removal and installation” in section 1g .
2.  Remove the air cleaner box cover. Refer to “air cleaner element removal and installation” in section 1d .
3.  Check the stva lead wire coupler (1) for loose or poor contacts.

4. Check whether the stvs open by turning the ignition switch on.

Is the operation ok?

• Loose or poor contacts on the stva coupler.
•  Open or short circuit in the b/lg, p/w, g or w/b wire.
•  If wire and connection are ok, go to step 2.

1. Turn the ignition switch off.
2.  Disconnect the stva lead wire coupler.
3.  Check the continuity between each terminal and ground.

Special tool (a): 09900–25008 (multi circuit tester set)

Tester knob indication resistance (Ω)

Stva continuity ∞Ω¶ (infinity) (terminal . Ground)

4. If ok, then measure the stva resistance (between the p wire “a” and b wire “b”) and (between the w/b wire “c” and g wire “d”).

Special tool (a): 09900–25008 (multi
circuit tester set)

Stva resistance approx. 6.5 Ω (terminal “a” – terminal “b”, terminal “c” – terminal “d”)

• B/lg, p/w, g and w/ b wire open or shorted to ground, or poor “3”, “4”, “27” and “28” connection.
•  If wire 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. Refer to “ecm removal and installation” in section 1c .

• Loose or poor contacts on the ecm coupler.
•  Replace the throttle body assembly with a new one. Refer to “throttle body disassembly and assembly” in section 1d .