International DT466 – ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS – IAH System (Inlet Air Heater)

The function diagram for the IAH system includes the following:
• IAH relays
• IAH relay connectors
• IAH elements
• Electronic Control Module (ECM)
• Barometric Absolute Pressure (BAP) sensor
• Engine Coolant Temperature (ECT) sensor
• Engine Oil Temperature (EOT) sensor
• Battery
• WAIT TO START lamp (amber)

The Inlet Air Heater (IAH) system warms the incoming air supply prior to cranking to aid cold engine starting
and reduce white smoke during warm-up.
The ECM is programmed to energize the IAH elements through the IAH relays while monitoring certain programmed conditions for engine coolant temperature, engine oil temperature, and atmospheric pressure.
The ECM monitors battery voltage and uses readings from the ECT, EOT, and BAP sensor to determine the amount of time that the WAIT TO START lamp is on, as well as the activation of the IAH system. The WAIT TO START lamp indicates when the IAH relays are activated and the elements are heating. The IAH system on-time can vary between zero seconds to forty-five seconds, depending on the ECT, EOT, and BAP sensor readings.
IAH elements are activated for a longer time period if the engine is cold or the barometric pressure is low
(high altitude).
The engine is ready to start when the WAIT TO START lamp is turned off by the ECM.
NOTE: The WAIT TO START lamp on-time is independent from the IAH system on-time.