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

### Circuit Description

The fuel tank pressure sensor will respond to changes in fuel tank pressure or in vacuum. The signal voltage from the fuel tank pressure sensor to the PCM varies according to changes in fuel tank pressure. The voltage signal can range from a high of over 4 volts to a low of 0.6 volts when the vent solenoid is closed.

### Conditions for Running the DTC

• | Engine coolant temperature is 70°C to 110°C (158°F to 230°F).

• | Intake air temperature is -10°C to 50°C (14°F to 122°F).

• | Barometric pressure is greater than 75kPa.

• | The fuel tank level is between 25 and 75 percent.

• | The engine has been running at idle for at least 2 minutes.

• | Fuel tank pressure is lower than a specified value after the completion of the EVAP system leakage check.

### Conditions for Setting the DTC

The fuel tank pressure that is indicated is lower than a specified value after the completion of the EVAP system leakage check.

### 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 that the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the DTC

• | The MIL turns OFF after 3 consecutive passing trips without a fault present.

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

• | Use the Clear DTC Information function of the scan tool, or disconnect the PCM battery feed in order to clear the DTC.

### Diagnostic Aids

Check for any of the following conditions:

• | A fuel tank pressure sensor that is shifted may cause DTC P0451 to set. Compare voltage readings with a known good sensor.

• | A plugged sensor air-vent hole. Inspect the sensor, and clean the sensor if necessary.

• | If DTC P0108, P0113, P0118,P0123, and P0450 are set together, check for an open ground circuit.

• | If DTC P0107, P0122, and P0450 are set together, check for an open reference circuit.

• | A faulty electrical connection at the PCM.

For functional checks of the EVAP control system components, refer to Evaporative Emission Control System Diagnosis

An intermittent malfunction may be caused by a fault in the electrical circuits of the EVAP control system . Inspect the wiring harness and the components for any of the following conditions:

• | Backed out terminals

• | Incorrect mating of terminals

• | Broken electrical connector locks

• | Incorrectly formed terminals or damaged terminals

• | Faulty terminal-to-wire connections

• | Physical damage to the wiring harness

• | A broken wire inside the insulation

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

If DTC P0451 cannot be duplicated, 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 Powertrain OBD System Check prompts the technician to complete basic checks, and to store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data that was taken when the fault occurred. The information is stored in the scan tool for later reference.

2. This step determines if a fault is present. With the fuel tank filler pipe open to the atmosphere, the fuel tank pressure sensor should read near zero. The reading from the fuel tank pressure sensor varies with changes in atmospheric pressure. The specified value in step 2 is typical of the atmospheric pressure near sea level.

3. This step determines if the fuel tank pressure sensor is OK. A voltage that is within the specified value indicates that the fault is in the sensor input circuit or in the PCM.

4. This step checks the operation of the EVAP canister vent solenoid. The output control of the EVAP canister vent solenoid is disabled if DTCs are stored, if engine speed is indicated, and until the engine reaches an operating temperature of at least 80°C (176°F).

5. This step tests for an EVAP canister vent solenoid that is stuck closed or is internally blocked .

6. This step checks for an EVAP canister vent solenoid that is stuck open or is leaking .

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. Install a scan tool.
2. Remove the fuel filler cap.
3. Turn ON the ignition, leaving the engine OFF.
4. Select the parameter for the fuel tank pressure sensor on the scan tool.

Did the scan tool display indicate fuel tank pressure within the specified value?

0.0-0.9 mm Hg (0.0-0.5 in H2O)

Go to Step 11

Go to Step 3

3 |

1. Remove the rear seat cushion. Refer to Rear Seat Cushion Replacement in Seats.
2. Disconnect the electrical connector C310 from the fuel tank pressure sensor .
3. Turn ON the ignition, leaving the engine OFF.
4. Connect a test lamp from the ignition positive voltage to the ground circuit terminal of connector C310 on the body harness side.

Did the test lamp illuminate?

--

Go to Step 4

Go to Step 8

4 |

1. Turn ON the ignition, leaving the engine OFF.
2. Use a DMM in order to measure the voltage of the sensor reference voltage circuit at connector C310 on the harness side.

Is the voltage at the specified value?

5.0 volts

Go to Step 5

Go to Step 7

5 |

1. Remove the sensor input wire from the C310 connector.
2. Reconnect the electrical connector to the fuel tank pressure sensor.
3. Remove the fuel filler cap.
4. Turn ON the ignition, leaving the engine OFF.
5. Measure the sensor input circuit voltage at the removed wire with a DMM that is connected to ground.

Was the voltage measured within the specified value?

2.0-2.6 volts

Go to Step 6

Go to Step 9

6 |

1. Inspect the sensor input circuit for a short and for an open between connector C310 and the PCM.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 20

7 |

1. Check for an open and for a short in the 5 volt reference circuit between connector C310 and the PCM.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 20

8 |

1. Check for an open in the sensor ground circuit between connector C310 and the PCM.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 20

9 |

1. Remove the fuel tank. Refer to Fuel Tank Replacement .
2. Remove the fuel tank pressure sensor from the fuel tank. Refer to Fuel Tank Pressure Sensor Replacement .
3. Visually inspect the sensor air vent hole and the air pressure inlet passage for clogging.
4. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 10

10 |

1. Inspect the sensor circuit between the sensor and the body harness connector C311 for any of the following conditions:

• | An open in the 5 volt reference circuit

• | An open in the sensor ground circuit

• | An open or a short in the sensor input circuit

2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 18

11 |

1. Remove the EVAP canister filter. Refer to Evaporative Emission Canister Filter Replacement .
2. Inspect the EVAP canister filter for any of the following conditions:

• | Contamination by water or by dirt

• | Blockage from dirt or from debris

3. Inspect the EVAP canister filter hoses for restrictions and for blockage.
4. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 12

12 |

1. Remove the rear seat cushion. Refer to Rear Seat Cushion Replacement in Seats.
2. Disconnect the electrical connector C311 from the fuel tank EVAP harness .
3. Turn ON the ignition, leaving the engine OFF.
4. Connect a test lamp from the ignition positive voltage terminal to the control circuit terminal of connector C311 on the body harness side.
5. Observe the test lamp while commanding the EVAP canister vent solenoid ON and OFF with the scan tool.

Did the test lamp illuminate only when the solenoid was commanded ON with the scan tool?

--

Go to Step 14

Go to Step 13

13 |

1. Inspect the circuit for any of the following conditions:

• | The ignition positive voltage circuit for an open

• | The solenoid control circuit for an open or a short

2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 20

14 |

1. Remove the fuel tank. Refer to Fuel Tank Replacement .
2. Inspect the EVAP system lines, the hoses, and the connections for restrictions.
3. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Step 15

15 |

1. Remove the EVAP canister vent solenoid.
2. Attempt to apply the specified value of vacuum to the canister side of the EVAP canister vent solenoid with a hand vacuum pump.

Does the EVAP canister vent solenoid hold vacuum?

15 in. Hg

Go to Step 19

Go to Step 16

16 |

1. Apply 12 volts to the EVAP canister vent solenoid.
2. Apply the specified value of vacuum to the canister side of the EVAP canister vent solenoid with a hand vacuum pump.

Does the EVAP canister vent solenoid hold vacuum?

15 in. Hg

Go to Step 17

Go to Step 19

17 |

1. Test for an open or for a short in the wiring harness between the solenoid and the body harness connector C311.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 21

Go to Diagnostic Aids

18 | Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the action complete? | -- | Go to Step 21 | --
19 | Replace the EVAP canister vent solenoid. Refer to Evaporative Emission Canister Vent Solenoid Replacement . Is the action complete? | -- | Go to Step 21 | --
20 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 21 | --
21 |

1. Use the scan tool in order to perform the Clear DTC Information function, and road-test the vehicle within the Freeze Frame conditions.
2. Review the scan tool data, and inspect for any DTCs. The repair is complete if DTCs are not stored.

Are any DTCs displayed on the scan tool?

--

Go to the applicable DTC table

System OK