For 1990-2009 cars
Engine Controls Components
Cell 20: EVAP Controls, IAC, PSP Switch
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Evaporative Emission (EVAP) control system prevents the emission of the fuel vapors. The fuel vapor generated in the fuel tank while driving or idling enters the EVAP canister where a charcoal element absorbs and stores the fuel vapor. When certain engine operating conditions are met the PCM purges the EVAP canister of stored vapors by turning ON the EVAP Canister Purge Solenoid Valve.

Emissions laws require that the PCM detect any leakage within the EVAP system. The PCM monitors the Fuel Tank Pressure sensor in order to detect any abnormalities within the EVAP system.

The PCM supplies a 5 volt reference voltage, a sensor ground and an input signal circuit to the Fuel Tank Pressure sensor.

### Conditions for Running the DTC

The engine has been running less than 10 seconds.

### Conditions for Setting the DTC

The fuel tank pressure sensor signal indicates less than -1.2 in. Hg for 7 seconds.

OR

The fuel tank pressure sensor signal indicates greater than +0.6 in. Hg for 7 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutively passing trips without a fault present.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the scan tool Clear DTC Information function.

### Diagnostic Aids

If DTCs P0105, P0110, P0115, and P0120 are also set, the malfunction may be in the sensor ground circuit.

If DTCs P0105 and P0120 are also set, the malfunction may be in the reference voltage circuit.

To perform a functional check of the fuel tank pressure sensor, refer to Evaporative Emission Control System Diagnosis .

An intermittent malfunction may be caused by a fault in the fuel tank pressure sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken electrical connectors locks.

• | Improperly formed or damaged terminals

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, splices, or terminals.

Repair any electrical circuit faults that were found. Refer to Wiring Repairs .

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

### Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks whether the fuel tank pressure sensor malfunction is present or intermittent. The input signal voltage of the fuel tank pressure sensor should indicate atmospheric pressure, 3.0 to 3.6 volts, with the fuel tank filler cap removed. The fuel tank pressure sensor voltage will vary with atmospheric pressure. A typical voltage at sea level is 3.2-3.3 volts.

3. This step determines if DTC P0450 is the result of a hard failure or an intermittent condition. Operating the vehicle in check mode enhances the PCM's diagnostic capabilities. For additional information on check mode operation refer to Powertrain Control Module Diagnosis.

4. This step checks whether there is trapped negative or positive pressure at the fuel tank pressure sensor.

5. Checks for an open or a short in the fuel tank pressure sensor 5 volt reference.

6. Checks for an open or short in the fuel tank pressure sensor input circuit.

7. Checks for an open in the fuel tank pressure sensor ground 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. Remove the fuel tank filler cap.
2. Disconnect the purge hose (canister side) at the EVAP canister purge solenoid valve.
3. Remove the left side driver compartment kick panel.
4. Turn ON the ignition, leaving the engine OFF.
5. Backprobe the fuel tank pressure sensor input circuit (BLU wire) at C221 with a DMM connected to ground.

Is the voltage within the specified value?

3.0-3.6 volts

Go to Step 3

Go to Step 4

3 |

1. Perform the scan tool Clear DTC Information function.
2. Place the vehicle into Check Mode using the scan tool.
3. Operate the vehicle within the Freeze Frame conditions as noted.

Does the DTC P0450 set?

--

Go to Step 6

Fault Not Present-Go to Diagnostic Aids

4 |

1. Disconnect the vapor pressure supply hose to the fuel tank pressure sensor.
2. Check the fuel tank pressure sensor input circuit voltage at C221 with the DMM.

Is the voltage within the specified value?

3.0-3.6 volts

Go to Step 5

Go to Step 6

5 |

1. Repair the cause of the trapped vapor pressure to the fuel tank pressure sensor. Check for any of the following conditions:

• | Pinched, crushed, or restricted EVAP lines and hoses

• | Blocked or restricted EVAP components

• | Faulty EVAP solenoids or EVAP canister. Refer to Evaporative Emission Control System Diagnosis .

2. Repair as necessary.

Is the action complete?

--

Go to Step 14

--

6 |

1. Turn OFF the ignition.
2. Disconnect the fuel tank pressure sensor electrical connector.
3. Turn ON the ignition, leaving the engine OFF.
4. Measure the voltage from the fuel tank pressure sensor connector cavity 3 (harness side), using a DMM.

Does the DMM read the specified value?

5.0 volts

Go to Step 7

Go to Step 8

7 | Measure the voltage from the fuel tank pressure sensor connector cavity 2 (harness side), using a DMM. Does the DMM read near the specified value? | 4.9 volts | Go to Step 10 | Go to Step 9
8 |

1. Check the fuel tank pressure sensor reference voltage circuit for an open or short.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 14

Go to Step 13

9 |

1. Check the fuel tank pressure sensor input circuit for an open or short. Check that the input circuit is not shorted to the sensor ground circuit.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 14

Go to Step 13

10 | Probe the fuel tank pressure sensor connector cavity 1 (harness side), with a test lamp connected to battery voltage. Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 11
11 |

1. Check for an open fuel tank pressure sensor ground circuit.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 14

Go to Step 13

12 | Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the action complete? | -- | Go to Step 14 | --
13 | Replace the PCM. Refer to Powertrain Control Module Replacement Is the action complete? | -- | Go to Step 14 | --
14 |

1. Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on scan tool?

--

Go to the applicable DTC table

System OK