Circuit Description
The evaporative emission (EVAP) system is used to store fuel vapors in order to reduce the amount of fuel vapors into the atmosphere. The fuel tank pressure (FTP) sensor is only used for EVAP system diagnostics. The FTP sensor is a transducer that varies resistance according to changes in the fuel tank pressure. The engine control module (ECM) monitors the FTP sensor signal in order to detect vacuum decay and excess vacuum during the EVAP system diagnostic test. The ECM supplies a 5 volt reference and a low reference circuit to the FTP sensor. If the ECM detects that the FTP sensor signal voltage is too low, this DTC sets.
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 |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0454 Fuel Tank Pressure (FTP) Sensor Circuit Intermittent.
Conditions for Running the DTC
The ignition is ON, or the engine is running.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The engine control module (ECM) will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF at the end of 3 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using the scan tool. |
Diagnostic Aids
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.
The FTP sensor on the scan tool should be between 2.35-2.85 volts with the ignition ON and the engine OFF and the fuel cap removed. This represents atmospheric pressure, or 0 inches of vacuum.
Step | Action | 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 DTC Information with a scan tool. Are DTCs P0451, P0452, or P0453,set? | Go to Step 3 | |
3 | Test for an intermittent and for a poor connection at the FTP sensor. 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 8 | Go to Step 4 |
4 | Test the FTP sensor signal circuit between the FTP sensor and the ECM for an intermittent open. Refer to Inducing Intermittent Fault Conditions , Circuit Testing , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 5 |
5 | Test the FTP sensor signal circuit between the FTP sensor and the ECM for an intermittent short to voltage. Refer to Inducing Intermittent Fault Conditions , Circuit Testing , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 6 |
6 | Test the low reference circuit for an intermittent open. Refer to Inducing Intermittent Fault Conditions , Circuit Testing , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 7 |
7 | Test for an intermittent and for a poor connection at the ECM. 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 8 | Go to Intermittent Conditions |
8 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 9 |
9 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
