Possible causes

– Faulty Intake Air Heater Relay
– Intake Air Heater Relay harness is open or shorted
– Intake Air Heater Relay 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 high with the relay ON, DTC P0542 will set. The ECM will only store info on first failure, It triggers the SES light on the second failure.

Symptoms

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

P0542 JEEP 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.