Circuit Description
The EVAP Pressure sensor is a sensor that changes resistance based upon fuel tank pressure (or vacuum). A vacuum is considered negative pressure.
The PCM provides a 5 volt reference and ground. The EVAP Pressure sensor signal varies between ground and 5 volts as fuel tank pressure varies. As pressure decreases (negative pressure, or vacuum), voltage increases. As pressure increases, voltage decreases (positive pressure, low voltage). The PCM uses the EVAP Pressure sensor values as an indicator of EVAP system efficiency. If the EVAP Pressure sensor signal goes high such as when the signal line is shorted to voltage or the EVAP Pressure sensor is shorted internally, this DTC will set.
Conditions for Running the DTC
| • | DTC P0601 is not set. |
| • | Fuel level at engine start up is the same or less than 85% full. |
| • | The Intake Air Temperature (IAT) at engine start up is between 2°C and 60°C. |
Conditions for Setting the DTC
The EVAP Pressure sensor reading has been 4.80 volts or higher.
Action Taken When the DTC Sets
| • | PCM turns ON the SERVICE EMISSION SYSTEM message. |
| • | PCM disables Evaporative Emission (EVAP) control solenoid. |
| • | The PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive drive trips that the diagnostic runs and fails. |
| • | The PCM will record operating conditions at the time the DTC sets. This information will be stored in the Freeze Frame and Failure Records. |
| • | A first failure of this DTC will store in Last Test Failed but not History. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail. |
| • | A Last Test Failed DTC will clear when the diagnostic runs and does not fail. |
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any diagnostic test. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in Powertrain Control Module Description . |
Diagnostic Aids
The EVAP Pressure Sensor monitors a range from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).
This vehicle is equipped with an access panel in the trunk compartment.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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If the EVAP Pressure sensor value is greater than 4.88 volts, an EVAP Pressure sensor circuit problem must be present.
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If the EVAP Pressure sensor value is less than 0.22 volts, the fault is the EVAP Pressure sensor or the reference voltage is higher than 5.50 volts.
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A high voltage reading on the 5 volt reference circuit could be caused by a short to voltage on another 5 volt reference circuit, some 5V Ref. circuits are shared inside the PCM, or battery voltage bleeding onto the 5 volt reference circuit as in a defective Linear EGR Valve.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
Is the value greater than the value specified? | 4.80 volts | Go to Step 3 | Fault not present, go to Diagnostic Aids. | |
Disconnect the EVAP pressure sensor. Is the EVAP pressure sensor value less than the value specified? | 0.22 volts | Go to Step 4 | Go to Step 5 | |
4 | Using DMM measure the voltage to ground at the EVAP Pressure sensor connector terminal C. Is the voltage higher than the value specified? | 5.3 volts | Go to Step 7 | Go to Step 8 |
5 | Using DMM measure the voltage to ground at the EVAP Pressure sensor connector terminal B. Is the voltage higher than the value specified? | 0.5 volts | Go to Step 6 | Go to Step 10 |
6 | Repair short to voltage on the EVAP Pressure Sensor Signal circuit. Is the repair complete? | -- | -- | |
Repair the short to voltage on the 5 volt Reference circuit. Refer to Test Descriptions. Is the repair complete? | -- | -- | ||
8 |
Was terminal contact repaired? | -- | Go to Step 9 | |
9 | Replace the EVAP Pressure sensor. Refer to EVAP Pressure sensor replacement. Is the replacement complete? | -- | -- | |
10 |
Was terminal contact repaired? | -- | Go to Step 11 | |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the replacement complete? | -- | -- |
