Diagnostic Instructions
DTC Descriptor
DTC P0181: Fuel Temperature Sensor Performance
Circuit/System Description
The fuel temperature sensor is a thermistor. The engine control module (ECM) supplies the fuel temperature sensor a bias 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 bias voltage cold and decreases 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.
Conditions for Running the DTC
| • | DTC P0117, P0118, P0182, P0183 are not set. |
| • | The engine must be turned OFF for 10 hours or longer. |
| • | Intake air temperature (IAT) sensor 1 reaches 10°C (50°F) with engine idling. |
| • | DTC P0181 will only run once per ignition cycle until a Pass, Fail, or Disable conditions exists. |
Conditions for Setting the DTC
| • | The fuel temperature and the ECT are more than 100°C (212°F) of each other at start-up. |
| • | The fuel temperature and the ECT are more than 10°C (50°F) of each other at start-up. |
| • | The IAT has dropped more than 5.3°C (42°F) after running more than 6 minutes 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. |
Diagnostic Aids
| • | A short to a separate 5-volt source may set this DTC. |
| • | A skewed sensor could result in driveability concerns. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Circuit/System Verification
Important: If you cannot duplicate the condition, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Turn ON the ignition and observe the Fuel Temperature Sensor parameter with a scan tool. The fuel temperature parameter should be within -30 to +120°C (-22 to +248°F).
Circuit/System Testing
- Disconnect the fuel temperature sensor .
- Turn ON the ignition, with the engine OFF.
- Observe the Fuel Temperature parameter with a scan tool.
| ⇒ | If the fuel temperature is warmer than -40° (-40°F), test the signal circuit for a short to ground. |
- Connect a 3A fused jumper wire between the fuel temperature sensor signal circuit and the low reference circuit.
| ⇒ | If the fuel temperature is colder than 120°C (248°F), test for high resistance in the signal circuit or the low reference circuit. |
- If all circuits test normal, refer to Component Testing in this diagnostic.
Component Testing
- Disconnect the fuel temperature sensor and measure the resistance of the sensor with a DMM.
- Record the values at varies engine temperatures and compare those results to the Temperature vs. Resistance Table (Fuel Temperature).
| ⇒ | If the sensor does not closely match through the temperature ranges, replace the fuel temperature sensor. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
