Diagnostic Instructions

DTC Descriptors

DTC P0451: Fuel Tank Pressure (FTP) Sensor Performance

DTC P0452: Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage

DTC P0453: Fuel Tank Pressure (FTP) Sensor Circuit High Voltage

DTC P0454: Fuel Tank Pressure (FTP) Sensor Intermittent

Diagnostic Fault Information

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
FTP Sensor Low Reference	--	P0446, P0451	P0446	--	P0451
FTP Sensor Signal	P0452	--	P0452	P0453	P0451, P0454
FTP Sensor 5-Volt Reference	P0452, P0530, P0641	P0451	P0446, P0453	P0453, P0530, P0641	--

Typical Scan Tool Data

FTP Sensor Voltage

Circuit	Normal Range	Short to Ground	Open	Short to Voltage
FTP Sensor Low Reference	0 V	--	0 V	--
FTP Sensor Signal	0 V	0 V	0-1.5 V	5 V
FTP Sensor 5-Volt Reference		0 V	0-1.5 V	5 V
With EVAP system vented to atmosphere

Circuit/System Description

The fuel tank pressure (FTP) sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The control module supplies a 5-volt reference circuit and a low reference circuit to the FTP sensor. The FTP sensor signal voltage varies depending on EVAP system pressure or vacuum. The controller also uses this FTP 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

P0452 and P0453

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

P0454

Conditions for Setting the DTC

P0451

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

P0452

The FTP sensor voltage is less than 0.1 volt for more than 5 seconds.

P0453

The FTP sensor voltage is more than 4.9 volts for more than 5 seconds.

P0454

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

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC

Diagnostic Aids

P0451

P0454

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Engine Controls Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

J 41413-200 Evaporative Emission System Tester (EEST)

Circuit/System Verification

P0451 and P0454

1. If DTCs P0452, P0453, or P0641 are set, repair those first.
2. With a scan tool, command the EVAP canister vent solenoid valve closed.
3. Command the purge solenoid to 30 percent.
4. Observe the FTP sensor voltage parameter as the vacuum increased to the abort limit.
5. The voltage should scale smoothly.

P0452 and P0453

1. Remove the fuel cap.
2. Turn ON the ignition, with the engine OFF.
3. Observe the Fuel Tank Pressure Sensor parameter with a scan tool.
4. The FTP Sensor parameter should be 1.5 volts.

Circuit/System Testing

P0451 and P0454

Important: Refer to the J 41413-200 operation manual for detailed instructions.

1. Start the engine with the J 41413-200 connected to the fuel filler neck.
2. Allow the engine to idle.
3. Use the Purge/Seal function to seal the system with a scan tool.
4. Command the EVAP canister purge solenoid valve to 30 percent.
5. Observe the vacuum/pressure gage on the J 41413-200 and the FTP parameter on the scan tool.
6. Allow the vacuum to increase on the gage of the J 41413-200 until it reaches approximately 16 inches H2O, or until the vacuum reached the abort limit on the scan tool.
7. Use the Purge/Seal function to seal the system with a scan tool.
8. If the difference between the FTP parameter on a scan tool and the vacuum/pressure gage on the J 41413-200 is more than 1 inch H2O, replace the FTP sensor.
9. If the Fuel Tank Pressure Sensor parameter on a scan tool display is less than 3.2 volts, replace the FTP sensor.

P0452 and P0453

1. If DTC P0641 is set, repair that DTC first.
2. With the ignition OFF, disconnect the harness connector at the FTP sensor.
3. With the ignition ON, the scan tool FTP sensor parameter should indicate 0 volts.

⇒	If the parameter is more than 0 volts, test for unexpected voltage at the signal circuit. If the circuit tests normal, replace the control module.

4. With the ignition ON, measure for 4.8-5.2 volts between the 5-volt reference circuit of the FTP sensor and ground.

⇒	If over 5.2 volts, test for unexpected voltage at the 5-volt reference circuit. If the circuit tests normal, replace the control module.

⇒	If under 4.8 volts, test for a short to ground, or open/high resistance at the 5-volt reference circuit. If the circuit tests normal, replace the control module.

5. With the ignition ON, the scan tool FTP sensor parameter should indicate 4.8-5.2 volts with a 3-amp fused jumper wire connecting the FTP signal circuit to the 5-volt reference circuit.

⇒	If under 4.8 volts, test for a short to ground or an open at the signal circuit. If the circuit tests normal, replace the control module.

⇒	If the circuits and control module test OK, replace the FTP sensor.

6. With the ignition OFF and the ECM powered down, measure for less than 50 ohms of resistance between the low reference circuit of the FTP sensor and a good ground.

⇒	If greater than 50 ohms, test for an open/high resistance in the circuit. If the circuit tests normal, replace the control module.

Component Testing

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.