Operation CHARM: Car repair manuals for everyone.
Home >> Fiat >> 2012 >> 500c L4-1.4L >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P0451

P0451






P0451-FUEL TANK PRESSURE SENSOR PERFORMANCE

For a complete wiring diagram, refer to the Wiring Information





Theory of Operation










The Evaporative Purge Monitor tests the integrity of the hoses/tube between the throttle body/intake and the fuel tank. At key off, the Powertrain Control Module (PCM) monitors the Evaporative System Integrity Monitor (ESIM) Switch. As the fuel and air in the Fuel Tank cools, a vacuum will occur naturally inside the tank. One inch of vacuum will cause the switch to close. If the PCM sees the switch close before the counter reaches a calibrated amount, the monitor passes.

The monitor is a two stage test and runs only after the Evaporative system passes the small leak test. Stage one is non-intrusive. With the engine running, the monitor will first evaluate the delta pressure change of the Fuel Tank Pressure (FTP) Sensor while normal purge control is active. If the monitor does not pass within a calibrated amount of time, then an intrusive monitor will be enabled. The intrusive test runs only if stage one does not pass. This intrusive monitor will ramp in the purge flow to a target amount while evaluating the delta pressure in the entire system. If the delta pressure between purge off and purge on exceeds a calibrated amount, then the monitor will ramp out the purge flow and evaluate the delta pressure between the high flow and the new low flow target. If the delta pressure is less than a calibrated threshold then the monitor will pass.

- When Monitored:
With the engine running at idle speed.

- Set Condition:
Low limit: The Fuel Tank Pressure Sensor voltage is less than 0.1 Volt for 10 seconds. High limit: The Fuel Tank Pressure Sensor voltage is greater than 4.7 Volts for 10 seconds. Signal curve: The Fuel Tank Pressure Sensor Performance code will be set if the signal remains constant.





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

Diagnostic Test

1. VEHICLE HISTORY AND SERVICE BULLETIN INVESTIGATION
1. Ignition on, engine not running.
2. With the scan tool, select View DTCs. Record the related Freeze Frame data if any DTCs are present.
3. Whether or not any DTCs are active you will want to check the following items which may assist in repairing the customer's complaint successfully:
- Check the vehicle's repair history.
- If the vehicle has a repair history that pertains to the customer's current complaint, review the repair.
- Inspect the vehicle for any aftermarket accessories that may have been installed incorrectly.
- Check for any service bulletin(s) related to the customer's complaint or DTCs.
- If a service bulletin applies, follow the instructions per the service bulletin.

Choose the following scenario that applies.

The service bulletin repaired the customer's complaint.

- Testing complete.

A DTC is present, no service bulletins apply or the service bulletin didn't repair the customer's complaint.

- Go To 2

2. ACTIVE DTC
1. Start the engine.
2. Allow the engine to idle.
3. With the scan tool, select View DTCs.

Is the DTC Active or Pending at this time?

Yes

- Go To 3

No

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

3. READ FUEL TANK PRESSURE

NOTE: If an Evap System DTC has been set, diagnose the Evap DTC before continuing.

1. Turn the ignition on.
2. With the Scantool, read the Fuel tank pressure.

Is the Fuel Tank Pressure above +30 hPa (0.435 psi)?

Yes

- Go To 4

No

- Go To 13

4. MEASURE THE FUEL TANK PRESSURE SENSOR SIGNAL CIRCUIT VOLTAGE
1. Turn the ignition off.
2. Disconnect the Fuel Tank Pressure Sensor harness connector.
3. Turn the ignition on.
4. Measure the voltage of the Fuel Tank Pressure Sensor Signal circuit at the Fuel Tank Pressure Sensor harness connector.

Is the voltage between 4.7 and 5.2 of a Volt?

Yes

- Go To 5

No

- If the voltage is above 5.2 of a Volt, Go To 11
- If the voltage is below 4.7 Volts, Go To 12

5. MEASURE THE 5 VOLT SUPPLY CIRCUIT VOLTAGE
1. With the ignition on.
2. Measure the voltage of the 5 Volt Supply circuit at the Fuel Tank Pressure Sensor harness connector.

Is the voltage between 4.7 and 5.2 Volts?

Yes

- Go To 6

No

- If the voltage is above 5.2 Volts, Go To 9
- If the voltage is below 4.7 Volts, Go To 10

6. FUEL TANK PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO 5 VOLT SUPPLY CIRCUIT
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Measure the resistance between the 5 Volt Supply circuit and the Fuel Tank Pressure Sensor Signal circuit at the Fuel Tank Pressure Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 7

No

- Repair the Fuel Tank Pressure Sensor Signal circuit for a short to the 5 Volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

7. SENSOR GROUND CIRCUIT OPEN
1. With the ignition off.
2. Measure the resistance of the Sensor Ground circuit from the Fuel Tank Pressure Sensor harness connector to the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 8

No

- Repair the Sensor Ground circuit for an open.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

8. FUEL TANK PRESSURE SENSOR
1. With the ignition off.
2. Reconnect the PCM C1 harness connector.
3. Connect a jumper wire between the Fuel Tank Pressure Sensor Signal circuit and the Sensor Ground circuit at the Fuel Tank Pressure Sensor harness connector.
4. Turn the ignition on.
5. With the Scantool, read the Fuel tank pressure.

Is the Fuel Tank Pressure below 1 hPa (0.02 psi)?

Yes

- Replace the Fuel Tank Pressure Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

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

9. 5 VOLT SUPPLY CIRCUIT SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Turn the ignition on.
4. Measure the voltage of the 5 Volt Supply circuit at the Fuel Tank Pressure Sensor harness connector.

Is the voltage below 1.0 Volt?

Yes

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

No

- Repair the 5 Volt Supply circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

10. 5 VOLT SUPPLY CIRCUIT OPEN
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Measure the resistance of the 5 Volt Supply circuit from the PCM harness connector to the Fuel Tank Pressure Sensor harness connector.

Is the resistance below 5.0 Ohms?

Yes

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

No

- Repair the 5 Volt Supply circuit for an open.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

11. FUEL TANK PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Disconnect the Fuel Tank Pressure Sensor connector.
4. Turn the ignition on.
5. Measure the voltage of the Fuel Tank Pressure Sensor Signal circuit at the Fuel Tank Pressure Sensor harness connector.

Is the voltage below 1.0 Volt?

Yes

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

No

- Repair the Fuel Tank Pressure Sensor Signal circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

12. FUEL TANK PRESSURE SENSOR SIGNAL CIRCUIT OPEN
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Measure the resistance of the Fuel Tank Pressure Sensor Signal circuit from the PCM C1 harness connector to the Fuel Tank Pressure Sensor harness connector.

Is the resistance below 5.0 Ohms?

Yes

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

No

- Repair the Fuel Tank Pressure Sensor Signal circuit for an open.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

13. FUEL TANK PRESSURE SENSOR
1. Turn the ignition off.
2. Disconnect the Fuel Tank Pressure Sensor harness connector.
3. Turn the ignition on.
4. Connect a fused jumper wire between the Fuel Tank Pressure Sensor Signal circuit and the Fuel Tank Pressure Sensor 5 Volt Supply circuit.
5. With the Scantool, read the Fuel tank pressure.

NOTE: Remove the fused jumper wire when this step is complete.

Is the Fuel Tank Pressure above +30 hPa (0.435 psi)?

Yes

- Replace the Fuel Tank Pressure Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 14

14. FUEL TANK PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the PCM harness connector.
3. Measure the resistance between ground and the Fuel Tank Pressure Sensor Signal circuit.

Is the resistance above 10k Ohms?

Yes

- Go To 15

No

- Repair the Fuel Tank Pressure Sensor Signal circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

15. FUEL TANK PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO SENSOR GROUND CIRCUIT
1. With the ignition off.
2. Measure the resistance between the Sensor Ground circuit and the Fuel Tank Pressure Sensor Signal circuit at the Fuel Tank Pressure Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 16

No

- Repair the Fuel Tank Pressure Sensor Signal circuit for a short to the Sensor Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

16. 5 VOLT SUPPLY CIRCUIT SHORT TO GROUND
1. With the ignition off.
2. Measure the resistance between ground and the 5 Volt Supply circuit.

Is the resistance above 10k Ohms?

Yes

- Go To 17

No

- Repair the 5 Volt Supply circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

17. 5 VOLT SUPPLY CIRCUIT SHORT TO SENSOR GROUND CIRCUIT
1. With the ignition off.
2. Measure the resistance between the 5 Volt Supply circuit and the Sensor Ground circuit at Fuel Tank Pressure Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

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

No

- Repair the 5 Volt Supply circuit for a short to the Sensor Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

pro multis · About Operation CHARM