Circuit Description
The PCM monitors the fuel tank pressure sensor signal to detect vacuum decay and excess vacuum during the enhanced EVAP diagnostic. The fuel tank pressure sensor measures the difference between the air pressure (or vacuum) in the tank and the outside air pressure. The PCM applies a 5.0 volt reference and ground to the sensor. The sensor will return a signal voltage between 0.1 and 4.9 volts. If the PCM detects a fuel tank pressure sensor signal that is excessively low, DTC P0452 will set.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The fuel tank pressure sensor signal is less than 0.1 volts. |
| • | The conditions is present for 1 second. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
Check for the following condition(s):
| • | Poor connection at the PCM or Fuel Tank Pressure Sensor. |
| Inspect harness connectors for backed out terminals, improper mating broken locks, improperly formed or damaged terminals, and poor terminal to wire conneciton. |
| • | Damaged harness. |
| Inspec the wiring harness for damage. If the harness appears to be OK, observe the Fuel Tank Pressure Sensor display on the scan tool while moving connectors and wiring related to the sensor. A change in the display will indicate the location of the malfunction. |
Test Description
Numbers below refer to the step numbers on the diagnostic table.
-
This step checks for an internally shorted A/C pressure sensor.
-
This step checks for an internally shorted FTP sensor.
-
This step determines whether the short to ground is the fault of the 5 volt reference B circuit wiring or the PCM.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 | Is DTC P1639 also set? | -- | ||
3 |
Does the FTP signal indicate a voltage near the specified value? | 5V | ||
4 |
Does the DMM display a voltage near the specified value? | 5V | ||
5 |
Was a problem found? | -- | ||
6 |
Was a problem found? | -- | ||
7 |
Was a problem found? | -- | ||
8 |
Was a problem found? | -- | ||
9 |
Was a problem found? | -- | ||
Is the FTP sensor signal voltage greater than the specified value? | 0.1V | |||
Is the A/C pressure sensor voltage display more than the specified value? | 0.1V | |||
Was a problem found? | -- | |||
13 | Replace the A/C pressure sensor. Is action complete? | -- | -- | |
14 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is action complete? | -- | -- | |
|
Important: Replacement PCM must be reprogrammed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is action complete? | -- | -- | ||
16 |
Does the scan tool indicate that DTC P0452 has failed this ign? | -- | System OK |
