Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P0540 Intake Air Heater A Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Some diesels – typically Cummins engines in Ram pick-ups and commercial vehicles, and Iveco – heat the intake air with a grid heater in the intake manifold instead of or alongside glow plugs. It draws very high current through a relay (on recent Ram a solid-state relay) and is switched by the engine module before and after starting; CARB requires cold-start aids to be monitored. Cummins checks it by the manifold temperature rise, Iveco by the battery voltage dip when the relay switches. P0540 is the general circuit fault of heater A without low/high assignment. No manufacturer document available to us uses this code; GM's Duramax LML has an intake heater but reports it under its own codes P154A–P154D.

Likely causes

Heater relay faulty (contacts welded or burnt, solid-state relay shorted)
Heating grid burnt out
Power cable or ring terminal corroded or overheated, control connector
Engine module driver

Symptoms

  • Check engine light on
  • Hard cold start, white smoke, rough cold idle
  • With welded relay: battery drained, heater stays on

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

intake air heaterheater relayheater wiringengine control module

Related codes

P0541P0542P0543P2604P2609P0380

References: patents.google.com, patents.google.com, gsi.ext.gm.com, static.nhtsa.gov.