P0110 fault code - Temperature sensor on a Citroën Saxo
P0110: Intake air temperature sensor - Circuit malfunction
The Citroën Saxo in this example has a 1.6 16V petrol engine rated at 118 hp.
The image (Fig. 1) shows a diagnostic scan of a Citroën Saxo 1.6 16V. Although no warning light was on, a scan with our EOBD Facile software revealed a fault. The ECU reported P0110, indicating a malfunction in the intake air temperature sensor circuit.
How an NTC sensor works
The vehicle's workshop manual tells us what type of sensor is fitted. Like most temperature sensors, it uses the NTC (negative temperature coefficient) principle: its electrical resistance changes with temperature. The workshop manual also shows where the sensor is located in the engine compartment.
Confirming the fault
With this information, the sensor is the first component to check. Using a multimeter set to measure resistance (Fig. 2), we measure across the sensor terminals. A "1" on the left of this meter's display indicates an open circuit, confirming that the sensor has failed.
After replacing the intake air temperature sensor, clear the fault code using the Clear button. The engine can now use the actual intake air temperature to adjust its operation. To check that the repair was successful, complete a drive cycle and run another OBD scan.
One question remains: why did this sensor failure not turn on a dashboard warning light? Not every fault triggers a driver warning. If the intake air temperature sensor fails, the engine control unit uses a default or estimated value in place of the unavailable measurement.
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