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Home >> Ford >> 2002 >> Crown Victoria Base, 4.6 9 >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> HVAC System - Automatic >> Self-Diagnostics >> Test B1251/B1253: In-Car Temperature Sensor Circuit Inoperative

Test B1251/B1253: In-Car Temperature Sensor Circuit Inoperative

  1. Turn ignition off. Disconnect in-car temperature sensor 2-pin harness connector, under top center of instrument panel. Measure resistance between in-car temperature sensor terminals. See TEMPERATURE SENSOR RESISTANCE TEST  table. If resistance is within specifications, go to next step. If resistance is not within specifications, replace in-car temperature sensor. Recheck system operation.
    TEMPERATURE SENSOR RESISTANCE TEST

    Temperature °F (°C) Ohms
    50-68 (10-20) 37,000-58,000
    68-86 (20-30) 24,000-37,000
    86-104 (30-40) 16,000-24,000
  2. Turn ignition on. Press AUTO button on EATC panel. Measure voltage between in-car temperature sensor harness connector White/Orange wire and Pink/Black wire terminals. If 4.7-5.1 volts exists, go to step  6. If voltage is not as specified, go to next step.
  3. Turn ignition off. Disconnect EATC module 13-pin harness connector C228. Measure resistance of White/Orange wire between EATC module harness connector C228 terminal No. 21 and in-car temperature sensor harness connector. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open in White/Orange wire. See WIRING DIAGRAMS . Recheck system operation.
  4. Turn ignition off. Measure resistance between ground and EATC module harness connector C228 terminal No. 21 (White/Orange wire). If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short to ground in White/Orange wire between in-car temperature sensor EATC module. See WIRING DIAGRAMS . Recheck system operation.
  5. Disconnect EATC module 13-pin harness connector C227. Measure resistance of Pink/Black wire between EATC module harness connector C227 terminal No. 4 and in-car temperature sensor harness connector. If resistance is less than 5 ohms, replace EATC module. Recheck system operation. If resistance is 5 ohms or more, repair open or high resistance in Pink/Black wire. See WIRING DIAGRAMS . Recheck system operation.
  6. Disconnect both EATC module 13-pin harness connectors C227 and C228. Inspect connector terminals for damage, loose fit or improper installation. If all wiring and connector terminals are undamaged and properly connected, replace EATC module. Recheck system operation. If wiring and/or connector terminals shows signs of damage or incorrect connections, repair as needed. Recheck system operation.
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