Ambient Temperature Sensor And Intake Air Temperature Plausibility Monitoring: General description: Notes

This section describes a new monitor that checks the plausibility of the ambient temperature (TAM) sensor with the intake air temperature (TIA) sensor. The ambient temperature signal is an input to the engine control unit via CAN from the instrument pack ECU and is used as part of the OBDII rate based monitoring criteria. As such it needs to be monitored by the OBDII system. Electrical checks of the TAM sensor are made by the instrument pack ECU. The air intake temperature sensor is a direct input to the engine control unit and is used as input to several OBD strategies. The TIA sensor is already monitored for electrical continuity and intermittent failure.

The result of the plausibility diagnosis gives 1 fault code defined as 'TIA or TAM implausible' and it will be specified in the service manual to check both sensors if this failure occurs.

The first part of the diagnosis is the 'engine cold check' however if the cold check criteria exceed a range then second 'engine hot check' is performed. This is shown schematically below.