4-52 FI SYSTEM DIAGNOSIS “C21” (P0110-H/L) IAT SENSOR CIRCUIT MALFUNCTION DETECTED CONDITION POSSIBLE CAUSE C21 Output voltage is not within the following • IAT sensor circuit open or short range. • IAT sensor malfunction 0.15 V Sensor voltage < 4.85 V • ECM malfunction P0110 H Sensor voltage is higher than specified • IAT sensor circuit open or ground circuit open value. L Sensor voltage is lower than specified • IAT sensor circuit shorted to ground value. IAT sensor ECM Dg IAT B/Br E2 E INSPECTION L 1 Step 1 (When indicating C21:) P 1) Turn the ignition switch OFF. 2) Lift and support the fuel tank. (5-3) M 3) Check the IAT sensor coupler for loose or poor contacts. A If OK, then measure the IAT sensor voltage at the wire side coupler. S 4) Disconnect the coupler and turn the ignition switch ON. 5) Measure the voltage between Dg wire terminal A and 1 ground. 6) If OK, then measure the voltage between Dg wire terminal A and B/Br wire terminal B. V IAT sensor input voltage: 4.5 – 5.5 V (+ Dg – - Ground) (+ Dg – - 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 Q or S) • Open or short circuit in the Dg wire or B/Br wire