Suzuki TU250X Service Manual page 180

Step 2
1) Turn the ignition switch OFF.
2) Connect the STP sensor coupler.
3) Insert the needle-point probes to the STP sensor coupler.
4) Disconnect the STVA lead wire coupler 1.
5) Turn the ignition switch ON.
6) Measure the STP sensor output voltage at the coupler
(between + Y wire and - B wire) by turning the fast idle cam
2 (secondary throttle valve close and open) with a finger.
 STP sensor output voltage
Secondary throttle valve is closed : Approx. 0.5 V
Secondary throttle valve is opened: Approx. 3.9 V
 09900-25008: Multi circuit tester set
09900-25009: Needle-point probe set
 Tester knob indication: Voltage ()
Is the voltage OK?
• R, Bl/Y or B/Br wire open or shorted to ground,
or poor A, J or T connection
• If wire and connection are OK, intermittent trou-
ble or faulty ECM.
YES
• Recheck each terminal and wire harness for
open circuit and poor connection.
• Replace the ECM with a known good one, and
inspect it again.
• Short circuit in the Bl/Y wire
NO • If check result is not satisfactory, replace STP
sensor with a new one.
FI SYSTEM DIAGNOSIS 4-59
2
2
Close
Open
2
ECM coupler (Harness side)