Circuit Description
The fuel temperature sensor is a thermistor. The engine control module (ECM) supplies the fuel temperature sensor a reference voltage of 5 volts on the signal circuit, and also provides a low reference circuit to the sensor. When the fuel temperature sensor is cold, the resistance is high. The fuel temperature sensor signal voltage remains near the supplied voltage cold, and decreases the signal voltage as the sensor warms. The control module monitors the fuel temperature sensor signal circuit in order to calculate the temperature of the fuel entering the engine.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0181 Fuel Temperature Sensor Performance
Conditions for Running the DTC
| • | DTC P0112, P0113, P0182, P0183, P0500, P2610 are not set. |
| • | The engine must be turned OFF for 10 hours or longer. |
| • | The start-up intake air temperature (IAT) is more than 15°C (59°F). |
| • | DTC P0181 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The fuel temperature and the engine coolant temperature (ECT) are more than 9.75°C (18°F) of each other at start-up. |
| • | The IAT has dropped less than 5.25°C (10°F) after running more than 400 seconds above 24 km/h (15 mph). |
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 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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if the IAT sensor reading is reading within a normal range. If the reading is outside of the specification, the IAT sensor may have a fault in the sensor or circuit.
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This step determines if the fault is present at the time of diagnosis.
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Reprogram the replacement ECM. Refer to the latest techline information for ECM programming.
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 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the scan tool indicate that the IAT parameter is within the specified value of the ambient temperature? | 9.75°C (18°F) | Go to Step 3 | Go to Step 4 | |
Does the DTC fail this ignition? | Go to Step 6 | Go to Intermittent Conditions | ||
4 |
Does the voltage measure near the specified value? | 5 V | Go to Step 5 | Go to Step 9 |
5 |
Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 11 |
6 |
Does the voltage measure near the specified value? | 5 V | Go to Step 8 | Go to Step 9 |
7 | Connect a 3-amp fused jumper wire between the fuel temperature sensor signal circuit and ground. Is the temperature more than the specified value? | 140°C (285°F) | Go to Step 8 | Go to Step 10 |
8 |
Does the test lamp illuminate? | -- | Go to Step 15 | Go to Step 11 |
9 |
Did you perform a repair? | -- | Go to Step 16 | Go to Step 12 |
10 | Repair the high resistance in the fuel temperature sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 16 | Go to Step 12 |
11 | Repair the open or the high resistance in the sensor low reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 16 | Go to Step 13 |
12 | Inspect the ECM connector terminals for spreading or poor connections. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 |
Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 16 | -- | |
14 | Replace the MAF sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- |
15 | Replace the fuel temperature sensor. Refer to Fuel Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- |
16 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 17 |
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
