For 1990-2009 cars
Engine Controls Components
Cell 20: Engine Data Sensors - TP, ECT, IAT and Fuel Tank
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Fuel Tank Pressure sensor is mounted to the sending unit at the top of the fuel tank. The Fuel Tank Pressure sensor measures the pressure changes within the EVAP system. The Fuel Tank Pressure sensor has a 5.0 volt reference, a ground and a signal circuit.

The Fuel Tank Pressure sensor contains a diaphragm which changes the resistance based on the pressure. When the EVAP system pressure is low (during the purge) the sensor output voltage is low. When the system pressure is high, the sensor output voltage is high.

When the ECM senses the Fuel Tank Pressure sensor signal voltage outside the normal operating range of the sensor, this DTC will set.

### Conditions for Running the DTC

#### Part 1:

Test continuously.

#### Part 2:

• | The engine is at idle.

• | The ECT is at start less than 33°C (91°F).

• | The engine is running between 2 to 10 seconds.

### Conditions for Setting the DTC

#### Part 1:

• | The tank pressure is greater than .27 kPa (1.1 in H2O).

• | The above condition met for at least 5 seconds

OR

• | The tank pressure is less than -.27 kPa (-1.1 in H2O).

• | The above condition met for at least 5 seconds.

#### Part 2:

• | The tank pressure is greater than 1.0 kPa (0.4 in H2O).

• | The above condition met for at least 3 seconds.

### Action Taken When the DTC Sets

The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.

### Conditions for Clearing the MIL/DTC

• | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes.

• | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.

• | The ECM battery voltage is interrupted.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

Check for the following conditions:

• | Poor connections at the ECM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Engine Control Module Diagnosis for the proper procedure.

• | Misrouted harness. Inspect the harness in order to ensure that the harness is not routed too close to any high voltage wires such as spark plug leads, or too close to any high current devices such as the alternator, the motors, the solenoids, etc.

• | Damaged harness. Inspect the wiring harness for any damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault.

If the sensor signal is only affected when the harness is moved at a component, and there is no problem with the harness or connections, the component may be damaged.

Refer to Symptoms for the Intermittents.

### Test Description

The number(s) below refer to the step number(s) on the Diagnostic Table.

1. Using the Freeze Frame data may aid in locating an intermittent condition. If the DTC cannot be duplicated, review the information in the Freeze Frame. Try to operate the vehicle within the same freeze frame conditions (the RPM, the MAF, the vehicle speed, the temperature, etc.) that were noted. This process may help in order to recreate the malfunction.

#### DTC P0450 - Evaporative Emission (EVAP) Fuel Tank Pressure Sensor Circuit

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn on the ignition with the engine off.
2. Remove the gas cap.
3. Monitor the Fuel Tank Pressure Volts with the scan tool.

Is the voltage within the specified range?

2.2 to 2.8 V

Go to Step 3

Go to Step 6

3 | Important: Before continuing with the diagnosis, zero the EVAP Pressure and Vacuum gauges on EVAP pressure/purge cart J 41413 (refer to the tool operating instructions).

1. Connect the EVAP pressure/purge cart J 41413 to the EVAP service port.
2. Replace the fuel cap.
3. Disconnect the Vent line at the EVAP Vent valve and block the line with a suitable stopper.
4. Pressurize the EVAP system to the specified value with the pressure/purge cart. Monitor the pressure with the gauge on the cart.
5. Monitor the Fuel Tank Pressure Volts with the scan tool.

Is the voltage within the specified range?

3.74 kPa (15 in. H20)

3.3 - 3.9 V

Go to Step 4

Go to Step 6

4 |

1. Turn on the ignition with the engine off.
2. Move the Fuel Tank Pressure sensor electrical connector, the harness and the ECM connector (by hand only) while observing the scan tool display.

Is the Fuel Tank Pressure Volts affected by moving the harness or connectors?

--

Go to Step 17

Go to Step 5

5 |

1. Turn on the ignition with the engine off.
2. Review the Freeze Frame data for this DTC and note the parameters.
3. Clear the DTCs.
4. Turn off the ignition for 15 seconds.
5. Start the engine.
6. Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in the Freeze Frame as possible. Refer to Conditions for Running the DTC.
7. Check for any DTCs.

Is this DTC set?

--

Go to Step 6

Refer to Diagnostic Aids

6 |

1. Disconnect the Fuel Tank Pressure sensor harness connector.
2. Measure the voltage from the Fuel Tank Pressure sensor signal circuit in the harness connector to battery ground with the DVM J 39200 .

Is the voltage within the specified range?

4.7-5.3 V

Go to Step 10

Go to Step 7

7 |

1. Turn off the ignition.
2. Leave the Fuel Tank Pressure sensor disconnected.
3. Disconnect the ECM.
4. Turn on the ignition.
5. Use the DVM J 39200 , measure the voltage from the Fuel Tank Pressure sensor signal circuit in the Fuel Tank Pressure sensor harness connector to battery ground.

Is there any voltage present?

--

Go to Step 21

Go to Step 8

8 | Check the harness for continuity of the Fuel Tank Pressure sensor signal circuit with the DVM J 33431-C . Is continuity indicated? | -- | Go to Step 9 | Go to Step 22
9 | Check the harness for continuity between the Fuel Tank Pressure sensor signal circuit and battery ground with the DVM J 39200 . Is continuity indicated? | -- | Go to Step 23 | Go to Step 27
10 | Measure the voltage from the Fuel Tank Pressure sensor 5 volt reference circuit in the Fuel Tank Pressure sensor harness connector to battery ground with the DVM J 39200 . Is the voltage within the specified range? | 4.7-5.3 V | Go to Step 14 | Go to Step 11
11 |

1. Turn off the ignition.
2. Leave the Fuel Tank Pressure sensor disconnected.
3. Disconnect the ECM.
4. Turn on the ignition.
5. Measure the voltage from the Fuel Tank Pressure sensor 5 volt reference circuit in the Fuel Tank Pressure sensor harness connector to battery ground with the DVM J 39200 .

Is there any voltage present?

--

Go to Step 18

Go to Step 12

12 | Check the harness for continuity of the Fuel Tank Pressure sensor 5 volt reference circuit with the DVM J 39200 . Is continuity indicated? | -- | Go to Step 13 | Go to Step 19
13 | Use the DVM J 39200 in order to check the harness for continuity between the Fuel Tank Pressure sensor 5 volt reference circuit and battery ground. Is continuity indicated? | -- | Go to Step 20 | Go to Step 27
14 |

1. Turn off the ignition.
2. Use the DVM J39200 in order to measure the resistance from the Fuel Tank Pressure sensor ground circuit in the Fuel Tank Pressure sensor harness connector to battery ground.

Is the resistance within the specified range?

0-5 ohms

Go to Step 16

Go to Step 15

15 |

1. Leave the Fuel Tank Pressure sensor disconnected.
2. Disconnect the ECM.
3. Check the harness for continuity of the Fuel Tank Pressure sensor ground circuit with the DVM J 39200 .

Is continuity indicated?

--

Go to Step 27

Go to Step 24

16 |

1. Turn on the ignition with the engine off.
2. Monitor the Fuel Tank Pressure sensor Voltage with the scan tool.
3. With a fused jumper wire, jumper the Fuel Tank Pressure sensor signal circuit to the Fuel Tank Pressure sensor ground circuit in the Fuel Tank Pressure sensor harness connector.

Does the scan tool indicate the specified voltage?

0 V

Go to Step 25

Go to Step 28

17 | Repair the harness/connections as necessary. Refer to Symptoms Is the action complete? | -- | Go to Step 29 | --
18 | Repair the short to voltage in the 5 volt reference circuit. Is the action complete? | -- | Go to Step 29 | --
19 | Repair the open/high resistance in the 5 volt reference circuit. Is the action complete? | -- | Go to Step 29 | --
20 | Repair the short to ground in the 5 volt reference circuit. Is the action complete? | -- | Go to Step 29 | --
21 | Repair the signal circuit that is shorted to voltage. Is the action complete? | -- | Go to Step 29 | --
22 | Repair the open/high resistance in the signal circuit. Is the action complete? | -- | Go to Step 29 | --
23 | Repair the short to ground in the signal circuit. Is the action complete? | -- | Go to Step 29 | --
24 | Repair the open/high resistance in the ground circuit. Is the action complete? | -- | Go to Step 29 | --
25 | Check for a poor connection or poor terminal tension at the Fuel Tank Pressure sensor harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Was a problem found and corrected?

--

Go to Step 29

Go to Step 26

26 | Replace the Fuel Tank Pressure sensor. Is the action complete? | -- | Go to Step 29 | --
27 | Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Was a problem found and corrected?

--

Go to Step 29

Go to Step 28

28 | Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 29

--

29 |

1. Clear the DTCs with the scan tool.
2. Turn off the ignition for 15 seconds.
3. Operate the vehicle with the conditions that are required for this vehicle to run. Refer to Conditions for Running the DTC.
4. Check for any DTCs.

Is this DTC set?

--

Go to Step 2

Go to Step 30

30 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK