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Super Mechanic
Super Mechanic, Master technician
Category: Chevy
Satisfied Customers: 16985
Experience:  29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering
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Code 0452 (evap low signal)what do you look for wrong in 2001 blazer?

Resolved Question:

code 0452 (evap low signal)what do you look for wrong in 2001 blazer?
Submitted: 7 years ago.
Category: Chevy
Expert:  Super Mechanic replied 7 years ago.

Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.

 

It sounds like there may be just a bad fuel tank pressure sensor, or connection at it. Here is how it can be tested, along with the description and particulars of the code setting.

 

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) monitors the Fuel Tank Pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the enhanced Evaporative Emission (EVAP) diagnostic The PCM supplies a 5-volt reference and ground to the sensor. The FTP sensor signal voltage increases as the fuel tank pressure decreases (negative pressure or vacuum, high voltage). The FTP sensor signal voltage decreases as the fuel tank pressure increases (positive pressure, low voltage). This Diagnostic Trouble Code (DTC) sets when the FTP sensor signal goes below a predetermined value.

CONDITIONS FOR RUNNING THE DTC
The engine is running.

CONDITIONS FOR SETTING THE DTC

  • The fuel tank pressure sensor voltage is less than 0.1 volts.
  • All conditions present for greater than 5 seconds.

ACTION TAKEN WHEN THE DTC SETS

  • The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
  • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

  • The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
  • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  • Use a scan tool in order to clear the MIL and the DTC.

TEST DESCRIPTION

 

 

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Customer: replied 7 years ago.
i replaced the fuel pump with a new one and had to rewire for a new type connector.that is the only change.i turned it (check engine)off with my scan but it came back on.
Expert:  Super Mechanic replied 7 years ago.

You will want to make sure of the connection at the fuel pressure sensor, (1) and related wiring. Or, the sensor might just be bad.

 

 

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