Circuit Description
The CNG fuel tank pressure (FTP) sensor is a pressure transducer. The fuel injector control module (FICM) supplies about 5 volts on the FTP sensor reference voltage circuit. The FICM also supplies a signal circuit and a low reference circuit 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 FICM communicates the FTP data to the powertrain control module (PCM) by a pulse width modulated (PWM) circuit. The PCM uses the FTP sensor and the fuel tank temperature (FTT) sensor in order to determine the amount of fuel within the fuel tank.
This DTC sets when the FTP sensor signal voltage is greater than the normal operating range of the sensor.
Conditions for Running the DTC
| • | The ignition voltage is more than 4 volts. |
| • | DTCs P0182, P0183, or P1207 are not set. |
| • | The fuel tank temperature (FTT) is less than 30°C (86°F). |
Conditions for Setting the DTC
| • | The FTP signal voltage is more than 4.95 volts. |
| • | The condition exists for at least 2 second. |
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.
-
This step determines if the condition is present.
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This step determines if an open sensor ground circuit condition is present. The FTP and FTT share a sensor ground. An open circuit between the splice and the ground terminal will cause both signal circuits to indicate high voltage.
-
This step determines if an open or shorted signal circuit is the cause of the condition.
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This step determines if a shorted 5-volt reference circuit is the cause of the condition.
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This step determines if an open sensor ground circuit between the harness connector of the FTP sensor and the splice is the cause of the condition.
Step | Action | Value(s) | 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) |
Does the scan tool display the FTP sensor voltage more than the specified value? | 4.95 V | Go to Step 4 | Go to Step 3 | |
3 |
Does the DTC fail this ignition cycle? | -- | Go to Step 4 | Go to Intermittent Conditions |
Observe the fuel tank temperature (FTT) sensor data parameter with a scan tool. Does the scan tool display the FTT sensor voltage more than the specified value? | 4.5 V | Go to Step 12 | Go to Step 5 | |
Important: If the jumper fuse opens, repair the signal circuit short to battery voltage. Does the scan tool display the FTP sensor voltage less than the specified value? | 0.25 V | Go to Step 6 | Go to Step 8 | |
Does the DMM display a voltage more than the specified value? | 5.2 V | Go to Step 9 | Go to Step 7 | |
Probe the ground circuit of the FTP sensor with a test lamp connected to B+. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 13 | |
8 | Test the signal circuit of the FTP sensor for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 11 |
9 | Test the 5-volt reference circuit of the FTP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 |
10 | Inspect for proper terminal contact 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 C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 |
11 | Inspect for proper terminal contact at the harness connector of the FICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 |
12 | Repair the ground circuit of the FTP sensor for an open between the ground terminal and the splice. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you complete the repair? | -- | Go to Step 16 | -- |
13 | Repair the ground circuit of the FTP sensor for an open, or high resistance, between the harness connector of the FTP sensor and the splice. Refer to Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual. Did you complete the repair? | -- | Go to Step 16 | -- |
14 | Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- |
15 | Replace the FICM. Refer to Fuel Injector Control Module Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- |
16 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 17 |
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
