GM Service Manual Online
For 1990-2009 cars only

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 P0450: Fuel Tank Pressure (FTP) Sensor Circuit

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

High Resistance

Open

Short to Voltage

Signal Performance

5-Volt Reference

*

--

P0450, P0453

**

--

FTP Sensor Signal

P0452

P0451

P0453

**P0453

P0451

Low Reference

--

P0451

P0450, P0453

--

--

*The vehicle may not start, not run, or stall

**Internal PCM or FTP sensor damage may occur if the circuit is shorted to B+

Typical Scan Tool Data

FTP Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: The engine coolant temperature is greater than 70°C (158°F) and the ignition is ON with the engine is OFF.

Parameter Normal Range: FTP Sensor 3.5-3.8 volts

5-Volt Reference

*

5.0 volts

--

FTP Sensor 1 Signal

**1.3-1.6 volts

4.6-5.0 volts

5.0 volts

Low Reference

--

4.6-5.0 volts

--

*The vehicle may not communicate with the scan tool when the 5-Volt reference circuit is shorted to ground

**Actual circuit voltage is not the same as scan tool displayed voltage

Circuit/System Description

The FTP sensor is used to detect any unexpected pressure in the EVAP system. The PCM supplies a 5-volt reference, an electrical ground, and a signal return circuit that has a 5-volt bias. The FTP sensor contains a silicon based chip that changes electrical resistance when pressure is applied. The sensor converts the positive or the negative pressure into an electrical signal and sends the signal to the PCM.

Fuel Tank Vapor Space

FTP mmHg

FTP Signal Voltage

Pressure

Positive Value

High

No Pressure

Near Zero

3.0-3.6V

Vacuum

Negative Value

Low

Conditions for Running the DTC

    • The engine is running.
    • The intake air temperature is between 4-35°C (40-95°F).
    • The DTC P0450, P0452 and P0453 run continuously once the above conditions are met.

Conditions for Setting the DTC

P0450

    • The FTP sensor signal voltage is less than 0.45 volts for 7 seconds.
        OR
    • The FTP sensor signal voltage is greater than 4.9 volts for 7 seconds.

P0452

The FTP sensor signal voltage is less than 0.45 volts for 7 seconds.

P0453

The FTP sensor signal voltage is greater than 4.9 volts for 7 seconds.

Action Taken When the DTC Sets

DTC P0450, P0452, and P453 are Type A DTCs.

Conditions for Clearing the DTC

DTC P0450, P0452, and P0453 are Type A DTCs.

Diagnostic Aids

    • DTCs P0606 and P0607 indicate the 5-volt reference circuit was shorted to ground. The engine may not start and the PCM may not communicate with the scan tool during a shot to ground in the 5-volt reference circuit.
    • The EVAP system diagnostic can be monitored on the scan tool under the I/M System Information selection. When the EVAP test displays a YES status, indicating that the system diagnostic is completed, check for DTC P0450, P0452, or P0453 in the Last Test Failed screen of the scan tool. If there is no FTP sensor DTC displayed the EVAP system diagnostic has run and passed, indicating that no malfunction was present this time. DTCs MUST be cleared in order to view the Current Status of the system diagnostics being performed. Do not forget that the I/M System Information tests only indicate that the test has run, not if the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Evaporative Emission Control 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 OFF, remove the fuel tank filler cap.
  2. Important: The FTP sensor reading will vary slightly with atmospheric pressure. The values indicated are for pressures at sea level.

  3. Ignition ON, observe the scan tool FTP sensor parameter. The reading should be between 3.5-3.8 volts.
  4. 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, disconnect the harness connector at the EVAP canister assembly.
  2. Ignition OFF, test for 10 ohms or less between the low reference circuit terminal 2 and ground G104.
  3. If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the PCM.
  4. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 4 and ground.
  5. If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the PCM.
    If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the PCM.
  6. Test for 4.8-5.2 volts between the FTP sensor signal circuit terminal 3 listed below and ground.
  7. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.
    If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the PCM.
  8. If all circuits test normal, replace the FTP sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Evaporative Emission System Vacuum Leak Pump Replacement
    •  Control Module References for control module replacement, setup, and programming