Circuit Description
The fuel tank pressure (FTP) sensor is a pressure transducer. The powertrain control module (PCM) supplies about 5 volts on the FTP sensor reference voltage circuit. The PCM also supplies low reference and signal circuits to the FTP sensor. When fuel level/tank pressure is full the FTP signal voltage rises to 4.1 volts. As fuel level/tank pressure decreases to empty, the FTP signal voltage drops to around 0.5 volts. The PCM monitors the FTP signal circuit voltage and the Fuel Tank Temperature (FTT) sensor and determines the amount of fuel within the fuel tank.
This DTC sets when the FTP sensor pressure has not dropped during vehicle operation.
Conditions for Running the DTC
| • | The engine is operating on alternative fuel. |
| • | The vehicle has been driven a certain number of miles. |
Conditions for Setting the DTC
The FTP pressure has not dropped during vehicle operation.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module switches over to gasoline fuel operation. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Monitor the scan tool data list after turning the ignition OFF. The PCM powers down after about 20 seconds and the scan tool will display a loss of communication.
This step tests the resistance of low reference circuit for the FTP sensor. The DMM should display less than 10 ohms when the PCM is not powered up.
-
This step test the 5 volt reference circuit of the FTP sensor. The DMM should display 5 volts if the circuit is OK.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Alternative Fuels (Engine Controls) |
2 |
Does the scan tool indicate that the FTP sensor voltage is more than the specified value? | 4.95 V | Go to Step 3 | Go to Step 4 |
Important: The PCM must be powered down during this test. Ensure that the scan tool has lost communication before proceeding. Does the DMM display a resistance less than the specified value? | 10ohms | Go to Step 8 | Go to Step 5 | |
Does the DMM display a voltage near the specified value? | 4.8 V | Go to Step 6 | Go to Step 7 | |
5 | Test the low reference circuit of the FTP sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
6 | Test the signal circuit of the FTP sensor for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
7 | Test the 5 volt reference circuit of the FTP sensor for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the FTP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 |
9 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the J Platform Service Manual. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
10 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement in the J Platform Service Manual. Did you complete the replacement? | -- | Go to Step 8 | -- |
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 |
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
