For 1990-2009 cars

### 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 (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, P0452 | P0453, P0530, P0641 | --

### Typical Scan Tool Data

#### FTP Sensor Voltage

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: With EVAP system vented to atmosphere Parameter Normal Range: 1.3-1.7 V
FTP Sensor Low Reference | 1.5 V | 4.6 V | --
FTP Sensor Signal | 0 V | 0 V | 5 V
FTP Sensor 5-Volt Reference | 0 V | 0 V | 5 V

### Circuit/System Description

The fuel tank pressure (FTP) sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The engine control module (ECM) 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.

### Conditions for Running the DTC

#### P0451

• | DTCs P0452, P0453, P0642, P0643 are not set.

• | The engine has been running for more than 10 seconds.

• | The FTP signal is between 0.2-4.9 volts.

• | The vehicle speed reached once during drive cycle of 20 kph (14.2 mph).

• | The EVAP system has reached full purge and no purge once during drive cycle.

• | The EVAP system is purging.

• | DTC P0451 runs continuously when the above conditions have been met.

#### P0452 and P0453

• | DTCs P0642 and P0643 are not set.

• | The average fuel level is between 6-40 liters (0-10 gallons).

• | DTCs P0452 and P0453 run continuously when the ignition is ON.

#### P0454

• | DTCs P000A, P000B, P0010, P0013, P0016, P0017, P0030, P0031, P0032, P0068, P0072, P0073, P0074, P009A, P0101, P0102, P0103, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0171, P0172, P0201, P0202, P0203, P0204, P0221, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0300, P0301, P0302, P0303, P0304, P0335, P0336, P0340, P0341, P0365, P0366, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0456, P0458, P0459, P0496, P0498, P0499, P0500, P0501, P0506, P0507, P0562, P0563, P0601, P0602, P0603, P0604, P0605, P0606, P0607, P061A, P061B, P061C, P0642, P0643, P1101, P2088, P2089, P2090, P2091, P2100, P2101, P2119, P2176, P2227, P2228, P2229, P2297, P2301, P2304, P2307, P2310, and P2A00 are not set.

• | The ignition is ON.

• | The barometric pressure (BARO) is more than 75 kPa.

• | The engine coolant temperature (ECT) is less than 110°C (230°F).

• | The engine has been running between 1-10 minutes.

• | The engine is idling.

• | The vehicle speed is 0 kph (0 mph).

• | The fuel level is between 6-40 liters (2-10 gallons).

• | The fuel tank pressure is between -3 and +1 kPa (-2 and +4 H2O).

• | The intake air temperature (IAT) is between -8.25 and +70°C (+17 and +158°F).

• | The battery voltage is more than 10 volts.

• | The engine is operating in Closed Loop fuel control.

• | DTC P0454 runs once per drive cycle when the above conditions have been met.

### Conditions for Setting the DTC

#### P0451

The maximum minus the minimum FTP signal voltage is less than 0.039 volt for 5 seconds.

#### P0452

The FTP sensor voltage is less than 0.1 volt for more than 1 second.

#### P0453

The FTP sensor voltage is more than 4.9 volts for more than 1 second.

#### P0454

The maximum minus the minimum fuel tank pressure is more than 0.1 kPa (0.4 in H2O) for 5 seconds.

### Action Taken When the DTC Sets

DTCs P0451, P0452, P0453, and P0454 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0451, P0452, P0453, and P0454 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 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 while taking a snapshot.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### 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. 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.
2. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the FTP sensor.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 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 ECM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 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 ECM.

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

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

⇒ | If greater than the specified range, test the signal circuit terminal 1 for a short to voltage. If the circuit tests normal, replace the ECM.

5. Install a 3A fused jumper wire between the signal circuit terminal 1 and the 5-volt reference circuit terminal 3. 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 ECM.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Fuel Tank Pressure Sensor Replacement

• | Control Module References for ECM replacement, setup, and programming