Engine management system - V8 (IAT output): Description and operation (page 2 of 3)

Should the IAT sensor fail, the ECM defaults to an assumed air temperature of 45 °C (113 °F).

The IAT sensor can fail the following ways or supply incorrect signal: l Sensor open circuit. l Short circuit to vehicle battery supply. l Short circuit to vehicle earth. l Increased sensor resistance. l Damaged sensor element.

In the event of an IAT sensor signal failure any of the following symptoms may be observed: l Adaptive fuelling disabled. l Idle speed adaption disabled. l Catalyst monitoring affected due to exhaust temperature model. l Idle speed actuator test disabled. l Warm up ignition angle affected. l Condenser fan hot restart inhibited.

There are two types of IAT sensor diagnostic checks: l The IAT sensor signal is less than the minimum threshold – the engine has to have been running for longer than 180 seconds, and idle speed control must have been operational for longer than 10 seconds. No fuel cut off is active. The IAT sensor signal must be less than -35°C (-31°F) for longer than 200 ms. l The IAT sensor signal is greater than the maximum threshold – the ECM has to be powered up (engine does not need to be running), and the signal must be greater than 140°C (284°F) for longer than 200 ms.

If the IAT sensor fails the following fault codes will be produced and can be retrieved by TestBook: