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Test C: Tank Temperature Sensor Circuit Failure (DTC B1222)

WARNING: This page is about a different car, the 2002 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Use correct probe adapter when probing or backprobing Natural Gas Vehicle Module (NGVM) harness connector. Failure to do so may damage NGVM harness connector.
NOTE: After making any repairs, clear DTCs and retest system.
  1. Turn ignition switch to RUN position. Using DVOM, measure voltage at Natural Gas Vehicle Module (NGVM) harness connector C1009 by backprobing between terminals No. 46 (Brown wire) and No. 47 (Light Green/Red wire). NGVM is located on center radiator support behind radiator. See Figure. If more than 4.5 volts exist, go to next step. If 4.5 volts or less exist, go to step  5.
  2. Turn ignition switch to LOCK position. Disconnect fuel tank temperature sensor harness connector C4128. Fuel tank pressure sensor is located in rear of in-bed fuel tank solenoid valve. Using a jumper wire, connect Light Green/Red wire terminal and Brown wire terminal at fuel tank temperature sensor harness connector C4128. Turn ignition switch to RUN position. Using DVOM, measure voltage at NGVM harness connector C1009 by backprobing between terminals No. 46 (Brown wire) and No. 47 (Light Green/Red wire). If more than .12 volt exists, go to next step. If .12 volt or less exists, replace fuel tank temperature sensor. See TANK TEMPERATURE SENSOR  under REMOVAL & INSTALLATION.
  3. Turn ignition switch to LOCK position. Disconnect NGVM harness connector C1009. NGVM is located on center radiator support behind radiator. Measure resistance in Brown wire between fuel tank temperature sensor harness connector C4128 and NGVM harness connector C1009 terminal No. 46. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in Brown wire between fuel tank temperature sensor and NGVM. See WIRING DIAGRAMS .
  4. Measure voltage at NGVM harness connector C1009 between terminals No. 40 (Brown/Yellow wire) and No. 46 (Brown wire). If voltage is .5 volt or less, go to next step. If voltage is more than .5 volt, repair short to voltage in Brown wire. See WIRING DIAGRAMS .
  5. Disconnect NGVM harness connector C1009. Turn ignition switch to RUN position. Using DVOM, measure voltage at NGVM harness connector C1009 between terminals No. 46 (Brown wire) and No. 47 (Light Green/Red wire). If voltage is 4.5 volts or less exists, go to next step. If voltage is more than 4.5 volts, replace fuel tank temperature sensor. See TANK TEMPERATURE SENSOR  under REMOVAL & INSTALLATION.
  6. Turn ignition switch to LOCK position. Disconnect NGVM harness connector C1009. Using DVOM, measure resistance at NGVM harness connector C1009 between terminals No. 40 (Brown/Yellow wire) and No. 46 (Brown wire). If resistance is more than 10 k/ohms, reconnect C1009 and go to next step. If resistance is 10 k/ohms or less, repair short to ground in Brown wire between NGVM and fuel tank pressure sensor. See WIRING DIAGRAMS .
    7. CAUTION: NGS tester MUST be used in this procedure to measure voltage. Using a standard DVOM to carry out this test will cause an inaccurate reading, possibly leading to inaccurate repairs.
  7. Connect fuel tank temperature sensor harness connector C4128. Connect accessory voltmeter leads to NGS tester. Measure voltage at NGVM harness connector C1009. Use positive lead of NGS tester to backprobe terminal No. 47 (Light Green/Red wire) and negative lead to backprobe terminal No. 40 (Black/Yellow wire). Turn ignition switch to RUN position. Enter DIGITAL MEASUREMENT SYSTEM on NGS tester. Select NGVM VOLTMETER, then LINK. Select PID/DATA, then NGVM. Select TEMPS1, then START. Select REC, then press TRIGGER to capture data. Press TRIGGER again to store data, then select VIEW to examine data. If voltage does not vary rapidly between .2 and 4.9 volts, go to next step. If voltage varies rapidly between .2 and 4.9 volts, repair intermittent contact condition.
  8. Turn ignition switch to LOCK position. Disconnect fuel tank temperature sensor harness connector C4128. Disconnect NGVM harness connector C1009. Check harness connectors for corrosion, and pushed-out or damaged terminals. Connect all disconnected components and retest system. Ensure harness connectors are properly seated. Using NGS tester, perform NGVM self-test. If DTC B1222 is still present, replace NGVM. See NATURAL GAS VEHICLE MODULE  under REMOVAL & INSTALLATION. If DTC B1222 is not still present, system is operating properly at this time.
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