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 PerformanceDTC 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, P0453 | P0453, P0530, P0641 | -- |
Typical Scan Tool Data
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
Operating Conditions: With EVAP system vented to atmosphere | ||||
FTP Sensor Low Reference | 0 V | -- | 0 V | -- |
FTP Sensor Signal | 0 V | 0 V | 0-1.5 V | 5 V |
FTP Sensor 5-Volt Reference | 0 V | 0-1.5 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 circuit and a low reference circuit to the FTP sensor. The FTP sensor signal voltage varies depending on EVAP system pressure or vacuum. The controller also uses this FTP signal to determine atmospheric pressure for use in the engine-off small leak test, DTC P0442. Before using this signal as an atmospheric reference, it must first be re-zeroed.
Conditions for Running the DTC
P0451
| • | DTC P0451 runs only when the engine-off natural vacuum small leak test, DTC P0442, executes. |
| • | The number of times this test runs can range from 0-2 per engine-off period. The length of the test can be up to 10 minutes. |
P0452 and P0453
DTCs P0452 and P0453 run continuously when the ignition is ON.
P0454
| • | DTC P0454 runs only when the engine-off natural vacuum small leak test, DTC P0442, executes. |
| • | This test can run once per engine-off period. The length of the test can be up to 10 minutes. |
| • | A refueling event is not detected. |
Conditions for Setting the DTC
P0451
This DTC will set if the controller is unable to re-zero the FTP sensor voltage within a calibrated range during the engine-off small leak test, DTC P0442.
P0452
The FTP sensor voltage is less than 0.1 volt for more than 5 seconds.
P0453
The FTP sensor voltage is more than 4.9 volts for more than 5 seconds.
P0454
If, during the engine-off natural vacuum small leak test, DTC P0442, the ECM detects an abrupt FTP signal change, other than a refueling event, this DTC will set. An abrupt change is defined as a change of 1 inch H2O in the span of 1 second.
Action Taken When the DTC Sets
P0451 and P0454
| • | The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records. |
P0452 and P0453
| • | The ECM illuminates the MIL on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The ECM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the ECM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the ECM records the operating conditions at the time of the failure. The ECM writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
P0451
| • | 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. By using the Purge Solenoid command on a scan tool, vacuum can be applied to the system instead of pressure. With the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, the vacuum should not increase to more than 9 inches H2O. |
| • | Ensure that the reference port on the FTP sensor is unobstructed. |
P0454
| • | This diagnostic is designed to detect an unexpected abrupt voltage signal change from the FTP. |
| • | Scan tool output controls, snapshot, and plot functions can help detect erratic sensor response. To look at the sensor signal under vacuum conditions, use Snapshot and the Purge/Seal function to capture data while commanding purge to 30 percent, then plot the data to look for erratic sensor operation. A similar inspection can be done for the pressure side of the sensor range by applying pressure with the J 41413-200 while taking a snapshot. |
| • | Ensure that the reference port on the FTP sensor is unobstructed. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Special Tools Required
J 41413-200 Evaporative Emission System Tester (EEST)
Circuit/System Verification
P0451 and P0454
- If DTCs P0452, P0453, or P0641 are set, repair those first.
- With a scan tool, command the EVAP canister vent solenoid valve closed.
- Command the purge solenoid to 30 percent.
- Observe the FTP sensor voltage parameter as the vacuum increased to the abort limit.
- The voltage should scale smoothly.
P0452 and P0453
- Remove the fuel cap.
- Turn ON the ignition, with the engine OFF.
- Observe the Fuel Tank Pressure Sensor parameter with a scan tool.
- The FTP Sensor parameter should be 1.5 volts.
Circuit/System Testing
P0451 and P0454
- Start the engine with the J 41413-200 connected to the fuel filler neck.
- Allow the engine to idle.
- Use the Purge/Seal function to seal the system with a scan tool.
- Command the EVAP canister purge solenoid valve to 30 percent.
- Observe the vacuum/pressure gage on the J 41413-200 and the FTP parameter on the scan tool.
- Allow the vacuum to increase on the gage of the J 41413-200 until it reaches approximately 16 inches H2O, or until the vacuum reached the abort limit on the scan tool.
- Use the Purge/Seal function to seal the system with a scan tool.
- If the difference between the FTP parameter on a scan tool and the vacuum/pressure gage on the J 41413-200 is more than 1 inch H2O, replace the FTP sensor.
- If the Fuel Tank Pressure Sensor parameter on a scan tool display is less than 3.2 volts, replace the FTP sensor.
Important: Refer to the J 41413-200 operation manual for detailed instructions.
P0452 and P0453
- If DTC P0641 is set, repair that DTC first.
- With the ignition OFF, disconnect the harness connector at the FTP sensor.
- With the ignition ON, the scan tool FTP sensor parameter should indicate 0 volts.
- With the ignition ON, measure for 4.8-5.2 volts between the 5-volt reference circuit of the FTP sensor and ground.
- With the ignition ON, the scan tool FTP sensor parameter should indicate 4.8-5.2 volts with a 3-amp fused jumper wire connecting the FTP signal circuit to the 5-volt reference circuit.
- With the ignition OFF and the ECM powered down, measure for less than 5 ohms of resistance between the low reference circuit of the FTP sensor and a good ground.
| ⇒ | If the parameter is more than 0 volts, test for unexpected voltage at the signal circuit. If the circuit tests normal, replace the ECM. |
| ⇒ | If over 5.2 volts, test for unexpected voltage at the 5-volt reference circuit. If the circuit tests normal, replace the ECM. |
| ⇒ | If under 4.8 volts, test for a short to ground, or open/high resistance at the 5-volt reference circuit. If the circuit tests normal, replace the ECM. |
| ⇒ | If under 4.8 volts, test for a short to ground or an open at the signal circuit. If the circuit tests normal, replace the ECM. |
| ⇒ | If the circuits and ECM test OK, replace the FTP sensor. |
| ⇒ | If greater than 5 ohms, test for an open/high resistance in the circuit. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
