Circuit Description
The DTC P2025 Fuel Vapor Temperature Sensor Performance diagnostic checks the accuracy of the fuel vapor temperature sensor signal. A thermistor is a resistor whose value varies with the temperature. The electrical resistance of the vapor temperature sensor is high when the fuel tank vapor temperature is cold, and the resistance is low when the vapor temperature is warm. The sensor is wired in series with a fixed resistor in the powertrain control module (PCM). The PCM applies 5 volts to the vapor temperature sensor. The PCM monitors the voltage across the sensor and converts the voltage into a temperature reading. The voltage measured by the PCM will be high when the vapor temperature is cold, and low when the vapor temperature is warm.
Temperature | Sensor Resistance | Sensor Signal Voltage |
|---|---|---|
Cold | High | High |
Warm | Low | Low |
Conditions for Running the DTC
| • | The engine is running. |
| • | The engine coolant temperature (ECT) sensor is less than 30°C (86°F) at engine start. |
| • | The engine coolant temperature (ECT) sensor and the intake air temperature (IAT) sensor are near the same temperature at engine start. |
Conditions for Setting the DTC
The signal from the fuel vapor temperature sensor indicates that there is a smaller change in the voltage than expected during a warm-up cycle.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns off after three consecutively passing trips without a fault present. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool clear DTC Information function in order to clear the DTC. |
Diagnostic Aids
The DTC P2025 diagnostic depends on the correct operation of the engine cooling system and ECT sensor. In order to evaluate the engine cooling system and ECT sensor, refer to DTC P0116 .
Use the Temperature vs Resistance table in order to check the fuel vapor temperature sensor at various temperature levels and evaluate the possibility of a shifted (incorrectly calibrated) sensor. A shifted sensor could result in a DTC P2025. Refer to Temperature Versus Resistance .
An intermittent malfunction may be caused by a problem in the fuel vapor temperature sensor electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .
If the DTC P2025 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step checks the integrity of the fuel vapor temperature sensor input circuit .
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This step checks the integrity of the fuel vapor temperature sensor ground circuit.
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Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P2025 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P2025 appears in the Not Ran Since Code Cleared list, the DTC P2025 diagnostic has not yet run. When the DTC P2025 does not appear in the Not Ran Since Code Cleared list, the DTC P2025 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P2025 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||
2 |
Is the IAT sensor value and the fuel vapor temperature sensor value within the specified degrees of one another? | 0°- 5°C (0° - 9°F) | Go to Diagnostic Aids | Go to Step 3 |
3 |
Is the fuel tank vapor temperature sensor display at the specified value? | -40°C (-40°F) | Go to Step 4 | Go to Step 7 |
4 |
Is the fuel tank vapor temperature sensor display at the specified value? | 165°C (329°F) | Go to Step 9 | Go to Step 5 |
Is the resistance more than the specified value? | 0.5 ohms | Go to Step 8 | Go to Step 6 | |
Measure the resistance of the vapor temperature sensor ground circuit from the sensor to the PCM with a DMM. Is the resistance more than the specified value? | 0.5 ohms | Go to Step 8 | Go to Step 11 | |
7 |
Did you find and correct a condition? | -- | Go to Step 12 | Go to Step 11 |
8 |
Did you complete the repair? | -- | Go to Step 12 | -- |
9 |
Was the measured resistance near the specified values in the table? | -- | Go to Step 11 | Go to Step 10 |
10 | Replace the fuel vapor temperature sensor. Refer to Fuel Vapor Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
Does the DTC run and pass? | -- | Go to Step 13 | Go to Step 2 | |
13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
