Circuit Description
The control module monitors the fuel tank pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the evaporative emission (EVAP) diagnostic test. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. If the control module detects the FTP sensor signal voltage below a calibrated value, this DTC will set.
The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.
FTP Sensor Signal Voltage | Fuel Tank Pressure |
|---|---|
High, Approximately 1.5 Volts or More | Negative Pressure/Vacuum |
Low, Approximately 1.5 Volts or Less | Positive Pressure |
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The FTP sensor voltage is less than 0.15 volts, for more than 10 seconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the DTC
| • | 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 non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
| • | The FTP sensor parameter on the scan tool should read between 1.30 and 1.70 volts with the ignition ON, engine OFF and the fuel cap removed. This represents atmospheric pressure of 0 inches H2O of vacuum. |
| • | The FTP sensor 5-volt reference circuit is shared with the following sensors: |
| - | The mass air flow (MAF) sensor |
| - | The air conditioning (A/C) pressure sensor |
| - | The accelerated pedal position (APP) sensor 1 |
| • | The FTP sensor low reference circuit is shared with fuel level sensors. |
| • | Inaccurate readings will occur if resistance measurements are taken on a FTP sensor. The FTP sensor contains an internal amplifier circuit that requires applied voltage to function properly. |
| • | To locate an intermittent problem, monitor the FTP sensor voltage with the ignition ON, engine OFF. Wiggling wires, while watching for change in the FTP sensor voltage, may help locate the area where a fault may exist. |
| • | For intermittent conditions, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
2 | Observe the fuel tank press. sensor parameter with a scan tool. Is the parameter less than the specified value? | 0.1 V | Go to Step 4 | Go to Step 3 | ||||||
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||||
4 |
Is the parameter less than the specified value? | 4.8 V | Go to Step 8 | Go to Step 5 | ||||||
5 |
Is the voltage within the specified value? | 4.8-5.2 V | Go to Step 9 | Go to Step 6 | ||||||
6 | Disconnect the following components, while monitoring the DMM:
Is the DMM within the specified value when any of the components are disconnected? | 4.8-5.2 V | Go to Step 12 | Go to Step 7 | ||||||
7 | Test the FTP 5-volt reference circuit for an open or for a short to ground between the fuel tank harness connector and the control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 | ||||||
8 | Test the signal circuit of the FTP sensor for a short to ground between the fuel tank harness connector and the control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 | ||||||
9 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 10 | ||||||
10 | Inspect for poor connections at the harness connector of the FTP sensor and fuel tank harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 | ||||||
11 | Inspect for poor connections at the harness connector of the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 | ||||||
12 | Replace the component that affected the 5-volt reference circuit. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement , Accelerator Pedal Position Sensor Replacement or Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
13 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
14 | Replace the control module. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
15 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 16 | ||||||
16 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
