The fuel temperature sensor is a thermistor that measures the temperature of the fuel being returned to the fuel tank. The engine control module (ECM) supplies the fuel temperature sensor a reference voltage of 5 volts on the signal circuit and a ground for the low reference circuit. When the fuel temperatures are low, the resistance is high. The signal voltage remains near the supplied voltage cold and decreases as the sensor warms. The ECM uses a fuel temperature rationality test to determine if the fuel temperature input is inaccurate. The ECM will record the amount of time the engine is OFF. During cold start the ECM will calculate the temperature difference between the fuel temperature sensor and the intake air temperature (IAT). Before failing this diagnostic, the ECM will perform a calculation to determine the presence of a block heater. If this diagnostic fails, DTC P0181 sets.
This diagnostic supports the following DTC:
DTC P0181 Fuel Temperature Sensor Performance
• | DTCs P0112, P0113, P0182, P0183, P0500, or P2610 are not set. |
• | The engine is running. |
• | The engine must be OFF for 10 hours or more. |
• | The start-up intake air temperature (IAT) is more than 15°C (59°F). |
• | DTC P0181 runs once per drive cycle within the enabling conditions. |
• | The ECM detects 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 decreased less than 5.25°C (10°F) after the engine has been running more than 400 seconds above 24 km/h (15 mph). |
• | 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. |
• | 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. |
• | Ensure that an engine block heater or front grill blanket is not being used at temperatures above -17C ( 0°F ). |
• | A engine block heater is used at temperatures above -17C ( 0°F ) this DTC may set. |
• | A front grill blanket is used at temperatures above -17C ( 0°F ) this DTC may set. |
• | If this DTC cannot be duplicated, the conditions may be intermittent. Refer to Intermittent Conditions . |
The numbers below refer to the step numbers on the diagnostic table.
This step determines if the IAT sensor is within the normal range. If the value is outside of the specification, the IAT sensor may be inaccurate or the circuit may have high resistance.
This step determines if the fault is present at the time of diagnosis.
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 - Engine Controls? | -- | Go to Step 2 | |||||||||
Important: The intake air temperature (IAT) sensor will start to warm-up as soon as the ignition is turned ON.
Does the scan tool indicate a temperature close to the ambient air temperature, within the specified range? | 10°C (18°F) | Go to Step 3 | Go to Step 5 | |||||||||
3 |
Is the difference between the Fuel Temperature Sensor parameter and the IAT Sensor parameter more than the specified value? | 10°C (18°F) | Go to Step 7 | Go to Step 4 | ||||||||
Does the DTC fail this ignition? | Go to Step 5 | Go to Diagnostic Aids | ||||||||||
5 |
is the voltage measured within the specified range? | 4.9-5.1 V | Go to Step 6 | Go to Step 8 | ||||||||
6 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 13 | Go to Step 11 | ||||||||
7 |
is the voltage measured within the specified Range? | 4.9-5.1 V | Go to Step 9 | Go to Step 10 | ||||||||
8 |
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 | ||||||||
9 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 12 | Go to Step 11 | ||||||||
10 | Repair the high resistance in the fuel temperature sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 | ||||||||
11 | Repair the open or the high resistance in the sensor low reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 | ||||||||
12 | Inspect the fuel temperature sensor for any of the following conditions:
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 | ||||||||
13 | Inspect the MAF/IAT sensor for any of the following conditions:
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 16 | ||||||||
14 | Test for intermittent and for poor connections at the ECM connector terminals. Repair as necessary. 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 18 | Go to Step 15 | ||||||||
Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- | |||||||||
16 | Replace the MAF/ IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- | ||||||||
17 | Replace the fuel temperature sensor. Refer to Fuel Temperature Sensor Replacement . 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 |