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

P0543 Intake Air Heater A Circuit Open

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. P0543 means an open circuit at heater A – in the control line or relay coil, or depending on the maker in the power circuit or heating element itself. It is detected by driver diagnosis with the output off, by a missing voltage dip on switching on or by a missing temperature rise. 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

Heating grid burnt out
Relay coil or contact open
Broken cable, loose nut or ring terminal at the grid
Fusible link in the heater circuit

Symptoms

  • Check engine light on
  • Starting problems in the cold
  • White smoke or knocking while warming up

Repair estimate

DifficultyMediumDIY possible
Parts and labour€40–450
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

P0540P0541P0542P2605P2609

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