VOLVO
ECM-1802 - Intake air temperature (IAT) sensor. Signal too low
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsS40 (1996–2004), V40 (1996–2004)
Show models by year and engine (2)
What does this fault code mean?
The ECM monitors the signal wire from the intake air temperature sensor. If the fault shows the signal is too low, the control module uses a fixed value for the air temperature instead.
Possible causes
- Signal wire short-circuited to ground
- Defective intake air temperature sensor
What you can do
- 1Switch off the ignition and check the connector on the mass air flow sensor, which has the intake air temperature sensor built in, for play and oxidation
- 2With a multimeter, check that the signal wire from the sensor is not shorted to ground
- 3If you have a diagnostic tool: read the air temperature in live data and check that it matches the surrounding air
- 4If the fault remains, have a workshop check or replace the mass air flow sensor, since the temperature sensor is built into it
Symptoms you may notice1
- No noticeable symptoms for the driver
What the fault can affect1
- The control module uses a fixed value for the air temperature
General guidance for car owners. Diagnosis on the car can point to a different cause.