4-68 FI SYSTEM DIAGNOSIS “C29” (P1654-H/L) STP SENSOR CIRCUIT MALFUNCTION DETECTED CONDITION POSSIBLE CAUSE C29 Signal voltage is not within the following • STP sensor maladjusted range. • STP sensor circuit open or short Difference between actual throttle open- • STP sensor malfunction ing and opening calculated by ECM is • ECM malfunction larger than specified value. 0.15 V Sensor voltage < 4.85 V P1654 H Sensor voltage is higher than specified • STP sensor circuit shorted to VCC or ground cir- value. cuit open L Sensor voltage is lower than specified • STP sensor circuit open or shorted to ground or value. VCC circuit open ECM BI R VCC Y Y/W STP B B/Br E2 E L STP sensor P INSPECTION M 1 Step 1 (When indicating C29:) A 1) Turn the ignition switch OFF. 2) Lift and support the fuel tank. (5-3) S 3) Check the STP sensor coupler for loose or poor contacts. If OK, then measure the STP sensor input voltage. 4) Disconnect the STP sensor coupler. 5) Turn the ignition switch ON. 6) Measure the voltage at the Red wire A and ground. 7) Also, measure the voltage at the Red wire A and B/Br wire C. STP sensor input voltage: 4.5 – 5.5 V 1 (+ Red – - Ground) V (+ Red – - B/Br) 09900-25008: Multi-circuit tester set Tester knob indication: Voltage () Is the voltage OK? YES Go to Step 2. • Loose or poor contacts on the ECM coupler NO (terminal A or S) • Open or short circuit in the Red wire or B/Br wire