Circuit Description
The DTC P0452 Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage diagnostic monitors the function of the FTP sensor circuit. The control module monitors the 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 |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0452 Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage
Conditions for Running the DTC
| • | DTC P0453 is not set. |
| • | The ignition is ON. |
| • | DTC P0452 runs once per drive cycle when the above conditions are met. |
Conditions for Setting the DTC
The FTP sensor voltage is less than 0.2 volt for more than 3 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 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. |
Diagnostic Aids
| • | The FTP sensor parameter on the scan tool should read between 1.4-1.5 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 exhaust gas recirculation (EGR) sensor |
| - | The A/C refrigerant pressure sensor |
| - | The A/T input shaft speed (ISS) sensor |
| - | The accelerator pedal position (APP) sensor 2 |
| • | 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 fault may exist. |
| • | For intermittent conditions, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
If DTC P0651 set, the 5-volt reference circuit may be shorted to ground.
-
This step tests for the proper operation of the circuit in the high voltage range.
-
After replacing the PCM, a new minimum throttle position and idle speed must also be established.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Is DTC P0651 also set? | -- | Go to DTC P0651 | Go to Step 3 | |
3 |
Does the scan tool indicate that the FTP sensor voltage is less than the specified value? | 0.1 V | Go to Step 5 | Go to Step 4 |
4 |
Does the DTC fail this ignition? | -- | Go to Step 5 | Go to Intermittent Conditions |
Does the scan tool indicate that the FTP voltage is at the specified value? | 5 V | Go to Step 8 | Go to Step 6 | |
6 | Test the 5-volt reference circuit of the FTP sensor for a short to ground, for high resistance, or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 |
7 | Test the signal circuit of the FTP sensor for a short to ground, for high resistance, or for an open. Refer to Circuit Testing and Wiring Repairs . 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 . 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 control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . 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 | -- |
Did you complete the replacement? | -- | Go to Step 12 | -- | |
12 |
Does the DTC run and pass? | -- | Go to Step 13 | Go to Step 2 |
13 | With the scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
