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 P0452: Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage
DTC P0453: Fuel Tank Pressure (FTP) Sensor Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5-Volt Reference | P0122, P0452, P0642 | P0452, P0641 | P0453, P0643 | P0641, P0642, P0643
FTP Sensor Signal | P0452 | P0452 | P0453 | --
Low Reference | -- | P0446 | -- | --

### Typical Scan Tool Data

#### FTP Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine operating in Closed Loop at idle Parameter Normal Range: 0.2-4.8 V
5-Volt Reference | 0 V | 0 V | 5 V
FTP Sensor Signal | 0 V | 0 V | 5 V
Low Reference | -- | 4.2 V | --

### Circuit/System Description

The evaporative emission (EVAP) system is used to store fuel vapors in order to reduce the amount of fuel vapors into the atmosphere. The fuel tank pressure (FTP) sensor is only used for EVAP system diagnostics. The FTP sensor is a transducer that varies resistance according to changes in the fuel tank pressure. The engine control module (ECM) monitors the FTP sensor signal in order to detect vacuum decay and excess vacuum during the EVAP system diagnostic test. The ECM supplies a 5-volt reference and a low reference circuit to the FTP sensor.

FTP Sensor Signal Voltage | Fuel Tank Pressure
--- | ---
High, Approximately 1.5 Volts or More | Negative Pressure/Vacuum
Low, Approximately 1.5 Volts or Less | Positive Pressure

### Conditions for Running the DTC

• | The engine speed is greater than 240 RPM.

• | The DTCs run continuously once the above conditions are met for 10 seconds.

### Conditions for Setting the DTC

#### P0452

The ECM detects the FTP sensor signal voltage is less than 0.2 volt for 4 seconds, or a cumulative of 30 seconds.

#### P0453

The ECM detects the FTP sensor signal voltage is greater than 4.85 volts for 4 seconds, or a cumulative of 30 seconds.

### Action Taken When the DTC Sets

DTC P0452 and P0453 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC P0452 and P0453 are Type B DTCs.

### Diagnostic Aids

If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Fuel System Description

#### 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

### Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. DTC P0641, P0642 or P0643 should not be set.

⇒ | If a DTC is set, refer to DTC P0641-P0643, P0651-P0653, or P0697-P0699.

2. Observe the FTP Sensor voltage parameter. The FTP sensor voltage should be between 0.2-4.8 V.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. 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, remove the fuse that supplies B+ to terminal X2-56 of the ECM.
2. Disconnect the pass thru multi-way harness connector X305, located on the underbody beneath the left front door.
3. Test for less than 5 Ω between the low reference circuit terminal E and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.

4. Install the fuse that supplies B+ to terminal X2-56 of the ECM.
5. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal H and ground.

⇒ | If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit/connections test normal, replace the ECM.

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

6. Observe the scan tool FTP sensor parameter. Verify that the FTP Sensor parameter is less than 4.8 V.

⇒ | If greater than the specified value, test the signal circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

7. Install a 3 A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal H. Verify that the scan tool FTP Sensor parameter is greater than 4.8 V.

⇒ | If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.

8. Remove the fuel tank. Refer to Fuel Tank Replacement.
9. Disconnect the FTP sensor connector.
10. Inspect the FTP sensor circuits in the fuel tank harness, between the FTP sensor connector and X305 for the following conditions, and repair as necessary:

• | Damaged wiring or terminals

• | Open circuits

• | Short to ground

• | Wire to wire short

11. If all circuits/connections 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