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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Catera 🢒 Engine 🢒 Engine Controls - 3.0L 🢒 DTC P0450 Fuel Tank Pressure Sensor Circuit

Object Number: 414118 Size: SF
Handling ESD Sensitive Parts Notice
Engine Controls Components
Cell 20: Fuel Controls
OBD II Symbol Description Notice

Circuit Description

The fuel tank pressure sensor is mounted to the sending unit at the top of the fuel tank. The fuel tank pressure sensor measures the pressure changes within the EVAP system. The fuel tank pressure sensor has a 5.0 volt reference circuit, a ground circuit, and a signal circuit.

The fuel tank pressure sensor contains a diaphragm that changes resistance as the pressure in the EVAP system changes. When the EVAP system pressure is low (during the purge) the sensor output voltage is low. When the system pressure is high, the sensor output voltage is high.

When the ECM senses the fuel tank pressure sensor signal voltage is outside the normal operating range, this DTC will set.

Conditions for Running the DTC

Part 1:

Test continuously.

Part 2:

    • The engine is at idle.
    • The engine coolant temperature (ECT) at start is less than 33°C (91°F).
    • The engine is running between 2 to 10 seconds.

Conditions for Setting the DTC

Part 1:

    • The tank pressure is greater than 0.03 kPa (11 in H2O).
    • The above condition met for at least 5 seconds

OR

    • The tank vacuum is greater than -0.03  kPa (-11 in H2O).
    • The above condition met for at least 5 seconds.

Part 2:

    • The tank pressure is greater than 0.00935 kPa (3.76 in H2O).
    • The above condition met for at least 3 seconds.

Action Taken When the DTC Sets

The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.

Conditions for Clearing the MIL/DTC
    • The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes.
    • A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.
    • The ECM battery voltage is interrupted.
    • The scan tool clears the MIL/DTC.

Diagnostic Aids

Notice: Using the J 35616-A Connector Test Adapter Kit will prevent damage to the harness connector terminals.

Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

Check for the following conditions:

    • Poor connections at the ECM or at the component -- Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Engine Control Module Diagnosis for the proper procedure.
    • A damaged harness -- Inspect the wiring harness for any damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help locate the fault.

If the sensor signal is only affected when the harness is moved at a component, and there is no problem with the harness or connections, the component may be damaged.

Refer to Symptoms for the Intermittents.

Test Description

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

  1. Using the Freeze Frame data may aid in locating an intermittent condition. If the DTC cannot be duplicated, review the information in the Freeze Frame. Try to operate the vehicle within the same Freeze Frame conditions, the RPM, the MAF, the vehicle speed, the temperature, etc., that were noted. This process may help in order to recreate the malfunction.

DTC P0450 EVAP Fuel Tank Pressure Sensor Circuit

Step

Action

Values

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. Turn ON the ignition leaving the engine OFF.
  2. Remove the gas cap.
  3. Using the scan tool, monitor the Fuel Tank Pressure Volts.

Is the voltage within the specified range?

2.2 to 2.8 V

Go to Step 3

Go to Step 6

3

Important: Before continuing with the diagnosis, zero the EVAP Pressure and Vacuum gauges on the J 41413 EVAP pressure/purge cart (refer to the tool operating instructions).

  1. Connect the J 41413 EVAP pressure/purge cart to the EVAP service port.
  2. Replace the fuel cap.
  3. Command the vent valve closed using a scan tool.
  4. Pressurize the EVAP system to the specified value with the pressure/purge cart. Monitor the pressure with the gauge on the cart.
  5. Monitor the Fuel Tank Pressure Volts with the scan tool.

Is the voltage within the specified range?

3.74 kPa (15 in. H2O)

4.5 - 4.9 V

Go to Step 4

Go to Step 6

4
  1. Turn ON the ignition leaving the engine OFF.
  2. Move the fuel tank pressure sensor electrical connector, the harness and the ECM connector (by hand only) while observing the scan tool display.

Is the Fuel Tank Pressure Volts affected by moving the harness or connectors?

--

Go to Step 16

Go to Step 5

5

  1. Turn ON the ignition leaving the engine OFF.
  2. Review the Freeze Frame data for this DTC and note the parameters.
  3. Clear the DTCs.
  4. Turn OFF the ignition for 15 seconds.
  5. Start the engine.
  6. Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in the Freeze Frame as possible. Refer to Conditions for Running the DTC.
  7. Check for any DTCs.

Is this DTC set?

--

Go to Step 6

Go to Diagnostic Aids

6
  1. Disconnect the fuel tank pressure sensor.
  2. Turn the ignition ON leaving the engine OFF.
  3. Measure the voltage from the Fuel Tank Pressure sensor 5 volt reference circuit in the fuel tank pressure sensor harness connector to a known good ground with the J 39200 DMM.

Is the voltage within the specified range?

4.7-5.3 V

Go to Step 7

Go to Step 11

7

Measure the voltage from the Fuel Tank Pressure sensor 5 volt reference circuit in the fuel tank pressure sensor harness connector to the sensor ground circuit with the J 39200 DMM.

Is the voltage within the specified range?

4.7-5.3 V

Go to Step 8

Go to Step 13

8

Measure the voltage from the Fuel Tank Pressure sensor SIGNAL circuit in the fuel tank pressure sensor harness connector to the sensor ground circuit with the J 39200 DMM.

Is the voltage within the specified range?

4.7-5.3 V

Go to Step 9

Go to Step 15

9

Using the scan tool, monitor the Fuel Tank Pressure Volts.

Is the voltage at the specified value?

5 V

Go to Step 10

Go to Step 20

10
  1. Using the scan tool, monitor the Fuel Tank Pressure Sensor Volts.
  2. With a fused jumper wire, jumper the fuel tank pressure sensor signal circuit to the fuel tank pressure sensor ground circuit in the fuel tank pressure sensor harness connector.

Does the scan tool indicate the specified voltage?

0 V

Go to Step 18

Go to Step 15

11

Was the voltage greater than the specified value?

5.3 V

Go to Step 17

Go to Step 12

12
  1. Turn the ignition OFF.
  2. Disconnect the ECM.
  3. Check the harness for continuity of the fuel tank pressure sensor 5 volt reference circuit with the J 39200 DMM. The DMM should indicate very low resistance.
  4. Use the J 39200 DMM in order to check the harness for continuity between the fuel tank pressure sensor 5 volt reference circuit and battery ground. The DMM should indicate OL.
  5. Use the J 39200 DMM in order to check the harness for continuity between the fuel tank pressure sensor 5 volt reference circuit and the SENSOR ground circuit. The DMM should indicate OL.
  6. Repair the wiring as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct a problem?

--

Go to Step 22

Go to Step 20

13
  1. Turn the ignition OFF.
  2. Disconnect the ECM.
  3. Check the harness for continuity of the fuel tank pressure sensor REF ground circuit with the J 39200 DMM. The DMM should indicate very low resistance.
  4. Repair the wiring as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct a problem?

--

Go to Step 22

Go to Step 20

14

Was the voltage greater than the specified value?

5.3 V

Go to Step 17

Go to Step 15

15
  1. Turn the ignition OFF.
  2. Disconnect the ECM.
  3. Check the harness for continuity of the fuel tank pressure sensor signal circuit with the J 39200 DMM. The DMM should indicate very low resistance.
  4. Use the J 39200 DMM in order to check the harness for continuity between the fuel tank pressure sensor signal circuit and battery ground. The DMM should indicate OL.
  5. Use the J 39200 DMM in order to check the harness for continuity between the fuel tank pressure sensor signal circuit and the SENSOR ground circuit. The DMM should indicate OL.
  6. Repair the wiring as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct a problem?

--

Go to Step 22

Go to Step 20

16

Repair the harness/connections as necessary. Refer to Symptoms .

Is the action complete?

--

Go to Step 22

--

17

Repair the short to voltage in the circuit.

Is the action complete?

--

Go to Step 22

--

18

Check for a poor connection or poor terminal tension at the fuel tank pressure sensor harness connector. Refer to Wiring Repairs in Wiring Systems. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Did you find and correct a problem?

--

Go to Step 22

Go to Step 19

19

Replace the fuel tank pressure sensor.

Is the action complete?

--

Go to Step 22

--

20

Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Wiring Repairs in Wiring Systems. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Did you find and correct a problem?

--

Go to Step 22

Go to Step 21

21

Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle.

Replace the ECM. Refer to Engine Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 22

--

22
  1. Use a scan tool in order to clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches the normal operating temperature.
  4. Select the DTC and the Specific DTC function.
  5. Enter the DTC number that was set.
  6. Operate the engine within the Conditions for Setting this DTC until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

Go to Step 2

Go to Step 23

23

Does the scan tool display any additional, undiagnosed DTCs?

--

Go to the applicable DTC table

System OK