P0543 FORD - Intake Air Heater 'A' Circuit Open
- Faulty Intake Air Heater (IAH) Relay
- Faulty Intake Air Heater
- Intake Air Heater Relay harness is open or shorted
- Intake Air Heater Relay circuit poor electrical connection
- Intake Air Heater harness is open or shorted
- Intake Air Heater circuit poor electrical connection
When is the code detected?The Engine Control Module (ECM) sends a bias voltage on diagnostic circuits one and two. If this voltage is not pulled low when the relay is OFF, or is high with the relay ON, DTC P0543 will set. The ECM will only store info on first failure, It triggers the SES light on the second failure.
- Engine Light ON (or Service Engine Soon Warning Light)
P0543 Ford DescriptionThe 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 operation. The control module will command the IAH ON when the engine coolant temperature is below 40 C (104 F). The power to the IAH heater is supplied by the battery positive voltage circuit through the IAH relay.
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