P0540
Intake Air Heater A Circuit
Intake Air Heater A Circuit: an electrical fault is present in the circuit. Used on diesel and some petrol engines for cold-start emissions and starting reliability.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Heater element open or shortedCommon
- Heater relay defectivePossible
- Wiring faultLess likely
Parts involved
- Intake Air Heater
- Heater Relay
- Heater Wiring
P0540 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.