P0542Intake Air Heater A Circuit High
- 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. P0542 means the voltage stays high although the heater is commanded on – a control line shorted to positive or a relay that does not switch. A shorted or welded relay can also power the heater permanently; Ram recalled 6.7 L Cummins trucks because a shorted heater relay could start a fire. 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
- Battery drained when heater stays on
- Burning smell or scorched wiring at the relay
- Likely causes
- LikelyHeater relay faulty (solid-state relay shorted, contacts stuck)
- PossibleControl line shorted to positive, harness chafed on a power cable
- PossiblePower circuit overheated, cable scorched
- 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.