P0540 OBD II Trouble Code Intake Air Heater A Circuit

How to diagnose, repair, and info on symptoms and causes of a P0540 engine code which applies to diesel vehicles with an air intake heater circuit problem. Also includes links to relevant forum discussions on the code.

Symptoms of P0540 OBD II Trouble Code

  • Engine will not start
  • Longer than normal cranking time
  • Check Engine Light illuminated
  • Rough idle at cold temperatures
  • Engine stalls

Common Causes of P0540 OBD II Trouble Code

  • Faulty heater element relay
  • Detective heater element
  • Faulty temperature sensor
  • Corroded or damaged connector
  • Damaged or restricted air duct
  • Faulty or damaged wiring
  • Defective Blower motor
  • Faulty PCM

Severity of P0540 OBD II Trouble Code

The severity of this code is normally moderate, but can be severe based on the specific malfunction.