Circuit Description
The fuel tank pressure (FTP) sensor is a pressure transducer. The Alternative Fuels ECM supplies about 5 volts on the FTP sensor reference voltage circuit. The Alternative Fuels ECM also supplies a ground circuit to the FTP sensor. When the fuel level/tank pressure is full, the FTP signal voltage rises to 4.1 volts. As the fuel level/tank pressure decreases to empty, the FTP signal voltage drops to around 0.5 volts. The Alternative Fuels ECM 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 signal voltage is greater than the normal operating range of the sensor.
Conditions for Running the DTC
| • | The engine is operating on alternative fuel. |
| • | The fuel temperature is less than 30°C (86°F). |
Conditions for Setting the DTC
The Alternative Fuels ECM monitors an FTP signal voltage of more than 4.70 volts for at least 1 second continuously.
Action Taken When the DTC Sets
| • | The Alternative Fuels ECM will NOT illuminate the MIL. |
| • | The Alternative Fuels ECM will store this DTC as History during one drive trip in which the diagnostic runs and fails. |
| • | The Alternative Fuels ECM will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data. |
Conditions for Clearing the DTC
| • | The Last Test Failed status will clear when the DTC runs and passes. |
| • | The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC. |
| • | All DTC Information can be cleared using 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 Alternative Fuels ECM 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.
-
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 | ||||||||
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? | 4.7 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? | 4.7 V | Go to Step 8 | 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 9 | |||||
Does the DMM display a voltage more than the specified value? | 5.2 V | Go to Step 10 | 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 11 | Go to Step 13 | |||||
8 | Test the ground circuit of the FTP sensor for an open between the Alternative Fuels ECM and the splice. 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 12 | ||||
9 | 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 12 | ||||
10 | 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 | ||||
11 | 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 | ||||
12 | Inspect for proper terminal contact at the harness connector of the Alternative Fuels ECM. 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 | ||||
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 15 | -- | ||||
15 | Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- | ||||
16 |
Does the DTC run and pass? | -- | Go to Step 17 | Go to Step 2 | ||||
17 | With a scan tool, select Capture Info in order to observe the stored information. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
