DTC P0540: Intake Air Heater - Incorrect Voltage
The Engine Control Module (ECM) uses an Intake Air Heater (IAH) to warm the incoming air for proper cylinder combustion. The ECM grounds the control coil of the IAH relay to energize the heater during cold weather operation. If the ECM detects voltage on the IAH circuit when the relay is commanded OFF, or incorrect voltage when the relay is commanded ON, this DTC will set.
There are several possible causes for this code including:
Faulty IAH Relay
Faulty IAH Relay Control Circuit
Faulty Line Voltage Reference Circuit
Faulty Heating Element
Faulty ECM
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