Description

Description

Ambient air temperature is supplied to the ECM by the instrument pack via the CAN communications network. In addition to the diagnostic checking for error messages from the instrument pack the ECM also performs plausibility checks on the received data.

When the engine is cold (i.e. not run for over 10 hours) the ambient air temperature signal is compared to the intake air temperature signal. If the temperature identified by the two signals is not within 6.8 degree C of each other then either a high or low ambient temperature fault is identified depending on which temperature is higher.

When the engine is hot the ambient temperature is continually checked against a modeled ambient temperature. If the actual temperature is not within 10.5 degree C of the modeled temperature then either a high or low ambient fault is identified depending on whether the actual temperature is high or low.