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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1383 (Engine Control System Diagnosis (DTC P0130 To DTC P0456) -- 1.8L (LNK)) >> Diagnosis >> DTC P0450 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 1:  The Diagnostic System Check- Engine Controls 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. 2:  This step determines if a FTP sensor malfunction is present. The input signal of the FTP sensor should indicate atmospheric pressure with the fuel tank filler cap removed. The fuel tank pressure sensor will vary with atmospheric pressure. A typical pressure at sea level is between 0.0-0.99 mm Hg (0.0-0.5 in H2O).
  3. 3:  This step determines if DTC P0450 is the result of a hard failure or an intermittent condition. Operating the vehicle in the Check Mode enhances the diagnostic capabilities of the PCM.
  4. 4:  This step checks whether there is trapped negative or positive pressure at the FTP sensor.
  5. 6:  This step checks for an open or a short in the FTP sensor 5-volt reference.
  6. 7:  The FTP sensor signal circuit carries a 5 volt bias that can be measured with the DMM. If the voltage is near zero there is an open, a short to ground, or a faulty PCM.
  7. 10:  This step checks for an open in the FTP sensor ground circuit.
DTC P0450

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
1  Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 
  1. Loosen the fuel tank filler cap in order to release any pressure inside the fuel tank.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the fuel tank pressure (FTP) sensor parameter on the scan tool.
Is the FTP sensor within the specified range?		 0.0-0.99 mm Hg (0.0-0.5 in H2O) 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. Refer to Service Bay Test .
  3. Operate the vehicle within the Freeze Frame conditions as noted.
Does DTC P0450 set?		 - Go to Step 6  Go to Diagnostic Aids
4 
  1. Remove the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement .
  2. Connect the FTP sensor electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the FTP sensor parameter on the scan tool.
Is the FTP sensor within the specified range?		 0.0-0.99 mm Hg (0.0-0.5 in H2O) Go to Step 5  Go to Step 6 
5 Repair the cause of the trapped vapor pressure in the fuel tank.
Is the action complete?		 - Go to Step 14  -
6 
  1. Turn OFF the ignition.
  2. Disconnect the FTP sensor electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Use a DMM in order to measure the reference circuit voltage on the harness side of the FTP sensor connector.
Does the voltage equal the specified value?		 5.0 V Go to Step 7  Go to Step 8 
7  Measure the voltage from the FTP sensor input circuit on the harness side using a DMM.
Is the voltage near the specified value?		 4.9 V Go to Step 10  Go to Step 9 
8 Repair the open in the reference voltage circuit of the FTP sensor between the sensor and SP108. Refer to Wiring Repairs in Wiring Systems.
Is the action complete?		 - Go to Step 14  -
9
  1. Inspect the FTP sensor input circuit for an open or a short. Verify 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 FTP sensor ground circuit on the harness side with a test lamp connected to B+.
Does the test lamp illuminate?		 - Go to Step 12  Go to Step 11 
11 Repair the open in the ground circuit of the FTP sensor between the sensor and the splice in the sensor ground circuit. Refer to Wiring Repairs in Wiring Systems.
Is the action complete?		 - Go to Step 14  -
12 Replace the FTP 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 (PCM) Replacement .
Is the action complete?		 - Go to Step 14  -
14
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC or until the EVAP test is complete. Review the supporting text.
Does the DTC run and pass?		 - Go to Step 15  Go to Step 2 
15 With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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