Fuel Tank Pressure Sensor Diagnosis
- Disconnect the electrical connector from the Fuel Tank Pressure (FTP) sensor.
- Turn ON the ignition, with the engine OFF.
- Measure the voltage between the 5-volt reference circuit and the sensor ground circuit with a DMM. The DMM should read 5.0 volts. See Fig 1 .
- If the measured voltage is not 5.0 volts for both tests, inspect for the following conditions:
- An open or a high resistance in the 5-volt reference circuit of the FTP sensor.
- An open or high resistance in the ground circuit of the FTP sensor.
- Measure the voltage from the input circuit of the FTP sensor to ground with the DMM. The DMM should read 4.5-5.5 volts.
- If the measured voltage is not 4.5-5.5 volts inspect for the following conditions:
- An open or high resistance in the input circuit of the FTP sensor.
- A short in the input circuit of the FTP sensor.
- Turn OFF the ignition.
- Connect the electrical connector to the FTP sensor.
- Disconnect the vacuum hose to the FTP sensor.
- Connect a hand held vacuum/pressure pump to the FTP sensor.
- Select the DC scale on the DMM.
- Connect one lead to the input circuit at C221 of the FTP sensor, and connect the other lead to ground. C221 is a 10-pin connector located behind the left front kick panel. It contains only the 3 wires for the FTP sensor.
- Measure the output voltage under the following conditions:
- Apply a vacuum of 0.59 in. Hg to the FTP sensor with a hand vacuum pump. Voltage should measure 1.3-2.1 volts.
- Release the vacuum from the FTP sensor. Voltage should measure 3.0-3.6 volts.
- Apply a pressure of 0.22 psi to the FTP sensor. Voltage should measure 4.2-4.8 volts.
- Replace the FTP sensor if the measured voltage is not within the test values listed above.
- Connect the vacuum hose to the FTP sensor.