Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

Possible Causes

- Inatake air heater circuit open or shorter - Faulty intake air heater relay - Faulty intake air hearter

Description

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 operation. The 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.