For 1990-2009 cars

### Circuit Description

The fuel tank pressure (FTP) sensor measures the difference between the air pressure or vacuum in the evaporative emission (EVAP) system, and the outside air pressure. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If the FTP sensor signal voltage increases above a calibrated value, 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 P0453 Fuel Tank Pressure (FTP) Sensor Circuit High Voltage

### Conditions for Running the DTC

• | The ignition is ON.

• | DTC P0453 runs continuously once the above conditions are met.

### Conditions for Setting the DTC

• | The fuel tank pressure (FTP) sensor voltage is more than 4.9 volts.

• | The above condition is present for more than 5 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.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step determines if the condition is present.

1. This step tests the signal circuit of the FTP sensor.

2. This step tests the ground circuit of the FTP sensor.

3. This step tests the 5-volt reference circuit of the FTP sensor.

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 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn OFF the ignition.
2. Remove the fuel cap.
3. Turn ON the ignition, with the engine OFF.
4. Observe the Fuel Tank Pressure Sensor parameter with a scan tool.

Is the Fuel Tank Pressure Sensor parameter more than the specified value?

4.3 V

Go to Step 4

Go to Step 3

3 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4 |

1. Install the fuel cap.
2. Disconnect the fuel tank pressure (FTP) sensor.
3. Observe the Fuel Tank Pressure Sensor parameter with a scan tool.

Is the Fuel Tank Pressure Sensor parameter more than the specified value?

0.2 V

Go to Step 7

Go to Step 5

5 | Measure the voltage on the FTP low reference circuit. Is the voltage below the specified value? | 1 V | Go to Step 6 | Go to Step 11
6 | Test the FTP low reference circuit for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 8
7 | Test the FTP signal circuit for a short to voltage or for a short to a 5-volt reference circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14
8 | Measure the voltage of the FTP 5-volt reference circuit with a DMM. Refer to Circuit Testing . Is the Fuel Tank Pressure Sensor parameter within the specified value? | 4.8-5.2 V | Go to Step 10 | Go to Step 12
9 | Test for an intermittent and for a poor connection at 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 15 | Go to Step 14
10 | 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 . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13
11 | Repair the short to voltage in the FTP low reference circuit. Did you complete the repair? | -- | Go to Step 15 | --
12 | Repair the short to voltage in the FTP 5-volt reference circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | 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 powertrain control module (PCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 15 | --
15 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

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? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK