DTC P0451, P0452, P0453, or P0454. Saturn ION 2006

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

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, P0452	P0453, P0530, P0641	--

Typical Scan Tool Data

FTP Sensor Voltage

Circuit	Normal Range	Short to Ground	Open	Short to Voltage
FTP Sensor Low Reference	--	1.5 V	4.6 V	--
FTP Sensor Signal	1.5 V	0 V	0 V	5 V
FTP Sensor 5-Volt Reference	--	0 V	0 V	5 V
¹With 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 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

•	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 FTP sensor voltage within a calibrated range during the engine-off small leak test, 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, 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

P0451 and P0454

•	The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

•	The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

P0452 and P0453

•	The control module illuminates the 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.

•	Clear the MIL and the DTC with a scan tool.

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 FTP sensor is unobstructed.

•

An FTP 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 (J 41413-100) while taking a snapshot.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

•	Engine Controls Connector End Views

•	Engine Control Module Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

•	Scan Tool Data List

•	Scan Tool Output Controls

Special Tools Required

J 41413-200 (J 41413-100) Evaporative Emission System Tester (EEST)

Circuit/System Verification

Ignition ON, observe the scan tool fuel tank pressure (FTP) sensor parameter. The reading should be between 1.3-1.7 volts with the fuel cap removed, and change with fuel tank pressure.

Circuit/System Testing

Ignition OFF, disconnect the harness connector at the FTP sensor.
Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal A and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the control module.

Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal C and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the control module.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the control module.

Verify the scan tool FTP sensor parameter is less than 0.1 volts.

⇒	If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the control module.

Install a 3-amp fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal C. Verify the scan tool FTP sensor parameter is greater than 4.7 volts.

⇒	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 control module.

If all circuits test normal, test or replace the FTP sensor.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Fuel Tank Pressure Sensor Replacement

•	Control Module References for engine control module (ECM) replacement, setup, and programming