4-72 FI SYSTEM DIAGNOSIS Step 3 3 1)Turn the ignition switch OFF. V 2)Connect the STP sensor coupler. 3)Insert the needle pointed probes to the STP sensor coupler. 4)Disconnect the STVA lead wire coupler. 5)Turn the ignition switch ON. 6)Measure the STP sensor output voltage at the coupler (between + Yellow wire and - Black wire) by turning the secondary throttle valve (close and open) with a finger. STP sensor output voltage 3 3 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 pointed probe set Tester knob indication: Voltage () Is the voltage OK? 3 E • Red, Y/W or B/Br wire open or shorted to ECM coupler (Harness side) (Black) (Gray) ground, or poor A, J or S connection L • If wire and connection are OK, intermittent trou- P YES ble or faulty ECM. • Recheck each terminal and wire harness for M open circuit and poor connection. A • Replace the ECM with a known good one, and inspect it again. S NO If check result is not satisfactory, replace STP sensor with a new one. After repairing the trouble, clear the DTC using SDS tool. (4-27)