P0540Intake Air Heater A Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine light on
- Hard cold start, white smoke, rough cold idle
- With welded relay: battery drained, heater stays on
- Likely causes
- LikelyHeater relay faulty (contacts welded or burnt, solid-state relay shorted)
- PossibleHeating grid burnt out
- PossiblePower cable or ring terminal corroded or overheated, control connector
- RareEngine module driver
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €50 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.