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DTC P0451-P0454 (LF1, LFW)

DTC P0451-P0454 (LF1, LFW)

Diagnostic Instructions


Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.


DTC Descriptors

DTC P0451

Fuel Tank Pressure Sensor Performance

DTC P0452

Fuel Tank Pressure Sensor Circuit Low Voltage

DTC P0453

Fuel Tank Pressure Sensor Circuit High Voltage

DTC P0454

Fuel Tank Pressure Sensor Intermittent

Diagnostic Fault Information

Circuit Short to Ground High Resistance Open Short to Voltage Signal Performance
Fuel Tank Pressure Sensor 5V Reference P0452, P0532, P0641 P0451 P0446, P0452 P0453, P0641 -
Fuel Tank Pressure Sensor Signal P0452 P0451 P0452 P0453 P0451, P0454
Fuel Tank Pressure Sensor Low Reference - P0446, P0451 P0446 - P0451


Typical Scan Tool Data

Fuel Tank Pressure Sensor Voltage

Circuit Short to Ground Open Short to Voltage
Operating conditions: Ignition ON, Engine OFF Parameter Normal Range: 1.3-1.7 V
Fuel Tank Pressure Sensor 5V Reference 0 V 0 V 4.2-5 V
Fuel Tank Pressure Sensor Signal 0 V 0 V 5 V
Fuel Tank Pressure Sensor Low Reference - 4.5 V -


Circuit/System Description

The fuel tank's pressure sensor measures the air pressure or vacuum in the EVAP system. The engine control module (ECM) supplies the sensor with a 5 V reference and a low reference circuit for the fuel tank's pressure sensor. The fuel tank pressure sensor signal voltage varies depending on EVAP system pressure or vacuum. The controller also uses this fuel tank pressure signal to determine atmospheric pressure for use in the engine-off small leak test, DTC P0442. Before using this signal as an atmospheric reference it must first be re-zeroed.

Conditions for Running the DTC


P0451

DTC P0451 runs only when the engine-off natural vacuum small leak test, P0442, executes.

The number of times this test runs can range from 0-2 per engine-off period. The length of the test can be up to 10 minutes.


P0452 and P0453

DTC P0452 and P0453 run continuously when the ignition is ON.


P0454

DTC P0454 runs only when the engine-off natural vacuum small leak test, P0442, executes.

This test can run once per engine-off period. The length of the test can be up to 10 minutes.

A refueling event is not detected.


Conditions for Setting the DTC

P0451

This DTC will set if the controller is unable to re-zero the fuel tank pressure sensor voltage within a calibrated range during the engine-off small leak test, P0442.

P0452

The fuel tank pressure sensor voltage is less than 0.1V for more than 5 seconds.

P0453

The fuel tank pressure sensor voltage is more than 4.9V for more than 5 seconds.

P0454

If, during the engine-off natural vacuum small leak test, P0442, the ECM detects an abrupt fuel tank pressure signal change, other than a refueling event, this DTC will set. An abrupt change is defined as a change of 0.45 inch H2O in the span of 1 second.

Action Taken When the DTC Sets


DTCs P0451 and P0454 are Type A DTCs.

DTCs P0452 and P0453 are Type B DTCs.


Conditions for Clearing the MIL/DTC


DTCs P0451 and P0454 are Type A DTCs

DTCs P0452 and P0453 are Type B DTCs


Diagnostic Aids


P0451 and P0454

A restriction in the EVAP canister or vent lines could prevent fuel vapor pressure from bleeding off fast enough. If the vent system cannot bleed off pressure fast enough, the re-zero procedure may not complete successfully, which could cause this code to set.

Ensure that the reference port on the fuel tank pressure sensor is unobstructed.

An fuel tank pressure sensor that is skewed or does not have a linear transition from low to high may cause this code to set. Scan tool output controls, snapshot, and plot functions can help detect erratic sensor response. To test the sensor signal under vacuum conditions, use the Quick Snapshot and the Purge/Seal functions to capture data while commanding purge to 20 percent, then plot the data to look for erratic sensor operation. A similar test can be done for the pressure side of the sensor operation by applying pressure with the J 41413-200 EEST while taking a snapshot.


Reference Information

Schematic Reference

Engine Controls Schematics (3.0L (LF1)) Engine Controls Schematics (2.8L (LAU))

Connector End View Reference

Component Connector End Views

Electrical Information Reference


Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs


DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 41413-200 Evaporative Emission System Tester (EEST)

Circuit/System Verification


1. Remove the fuel cap.

2. Ignition ON, engine OFF.

3. Observe the Fuel Tank Pressure Sensor parameter with a scan tool.

4. The Fuel Tank Pressure Sensor parameter should be 1.3-1.7 V.


Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the B150 fuel tank pressure sensor.

2. Ignition OFF, test for less than 5 Ω of resistance between the low reference circuit terminal 2 and ground.

3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

4. Ignition ON, test for 4.8-5.2V between the 5V reference circuit terminal 3 and ground.

5. If less than the specified range, test the 5V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

6. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

7. Verify the scan tool B150 fuel tank pressure sensor parameter is less than 0.2V.

8. If greater than the specified range, test the signal circuit's pin 1 for a short to voltage. If the circuit tests normal, replace the K20 ECM.

9. Install a 3A fused jumper wire between the signal circuit terminal 1 and the 5V reference circuit terminal 3. Verify the scan tool fuel tank pressure sensor parameter is greater than 4.7V.

10. If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

11. If all circuits test normal, test or replace the B150 fuel tank pressure sensor.


Repair Instructions


Fuel Tank Pressure Sensor Replacement

For DTC P0452 or P0453, always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

For DTC P0451 or P0454, clear DTCs with a scan tool.

Control Module References for ECM replacement, setup, and programming