P1456

P1456-FUEL TANK PRESSURE SENSOR CIRCUIT LOW

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

The Fuel Tank Pressure (FTP) sensor provides the Powertrain Control Module (PCM) with information on vapor pressure inside the fuel tank. The FTP sensor is a transducer that varies resistance according to changes in pressure. The PCM provides a 5 volt supply and sensor ground. The sensor sends a feedback voltage to the PCM on the signal circuit. As the fuel tank pressure increases, the feedback voltage decreases.

- When Monitored:
With the Ignition on.

- Set Condition:
The Powertrain Control Module (PCM) detects that the Fuel Tank Pressure (FTP) sensor input voltage is below 0.372 volts (3.975 kPa) for at least 5 seconds. One Trip Fault.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, read DTCs.

NOTE: Diagnose and repair any system voltage or 5-Volt Sensor Reference DTCs before continuing with this test.

Does the scan tool display this DTC as active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. CHECK THE (N8) FTP SENSOR SUPPLY CIRCUIT FOR VOLTAGE
1. Turn the ignition off.
2. Disconnect the FTP Sensor harness connector.
3. Turn the ignition on.
4. Measure the voltage on the (N8) FTP Sensor Supply circuit at the FTP Sensor harness connector.

Is the voltage between 4.8 and 5.2 Volts?

Yes

- Go To 3

No

- Go To 6

3. CHECK THE (N7) FTP SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Disconnect the FTP Sensor harness connector.
2. With the scan tool, monitor the FTP Sensor voltage with the FTP Sensor harness connector disconnected.

NOTE: The sensor voltage should be approximately 5.0 volts (plus or minus.1 volts) with the connector disconnected.

Does the scan tool display the voltage as described above?

Yes

- Verify that there is good pin to terminal contact in the FTP Sensor and Powertrain Control Module connectors. Replace the FTP Sensor if no problems were found with the connectors. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 4

4. CHECK THE (N7) FTP SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Measure the resistance between ground and the (N7) FTP Sensor Signal circuit at the FTP Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 5

No

- Repair the short to ground in the (N7) FTP Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. CHECK FOR THE (N7) FTP SENSOR SIGNAL CIRCUIT SHORTED TO THE (N10) FTP SENSOR RETURN CIRCUIT
1. Measure the resistance between the (N7) FTP Sensor Signal circuit and the (N10) FTP Sensor Return circuit at the FTP Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 6

No

- Repair the short between the (N7) FTP Sensor Signal circuit and the (N10) FTP Sensor Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors for the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.