Circuit 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. If the ECM detects that the FTP sensor signal voltage is too high, this DTC sets.
The following table illustrates the relationship between the FTP sensor signal voltage and the EVAP system pressure/vacuum.
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 |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0453 Fuel Tank Pressure (FTP) Sensor Circuit High Voltage
Conditions for Running the DTC
| • | The engine is operating for more than 3 seconds. |
| • | DTC P0453 runs continuously once the above condition is met. |
Conditions for Setting the DTC
| • | The ECM detects the FTP sensor signal voltage is more than 4.6 volts. |
| • | The condition is present for more than 4 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module 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 4 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
| • | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. |
| • | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views . |
| • | A refueling event may cause this DTC to set. |
| • | A blocked or clogged EVAP canister may cause this DTC to set. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the condition is present.
-
This step tests the EVAP atmospheric vent for a restriction. Inspect the vent for a restriction if the FTP voltage drops after removing the fuel fill cap.
-
This step tests for high resistance in the low reference circuit of the FTP sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to power down completely.
-
This step tests the low reference circuit for a short to voltage. A short to voltage on the low reference circuit will damage the ECM. Repair the short to voltage before replacing the ECM, if the voltage on the low reference circuit is more than the specified value.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Is the voltage less than the specified value? | 4.5 V | Go to Step 3 | Go to Step 4 | |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids |
Is the voltage more than the specified value? | 4.5 V | Go to Step 5 | Go to Step 15 | |
5 |
Is the voltage less than the specified value? | 0.1 V | Go to Step 6 | Go to Step 9 |
6 | Measure the voltage between the 5-volt reference circuit of the FTP sensor and a good ground, with a DMM. Is the voltage less than the specified value? | 6 V | Go to Step 8 | Go to Step 11 |
|
Notice: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
Is the resistance more than the specified value? | 5 ohms | Go to Step 8 | Go to Step 12 | |
Is the voltage less than the specified value? | 1 V | Go to Step 10 | Go to Step 14 | |
9 | Test the signal circuit of the FTP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
10 | Test the low reference circuit of the FTP sensor for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
11 |
Important: The engine control module (ECM) for this engine is not equipped with 5-volt reference DTCs. The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors. Test the 5-volt reference circuit of the FTP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
12 | Test for shorted terminals and for poor connections at the FTP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 16 |
13 | Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 |
14 |
Important: The control module and/or the FTP sensor may be damaged if the circuit is shorted to battery positive voltage. Repair the short to voltage in the low reference circuit of the FTP sensor. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 18 | -- |
15 | Repair the restriction in the EVAP canister atmospheric vent pipe. Did you complete the repair? | -- | Go to Step 18 | -- |
16 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- |
17 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 18 | -- |
18 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 19 |
19 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
