Cause
Failed intake air heater relay
The relay switching the grid heater that warms intake air on a cold diesel. It carries very high current for a short period, which is what wears the contacts — and since the heater only runs in cold weather, the fault is seasonal and often reported as the car being difficult only in winter.
Typically an easy fix. Often worth checking before paying anyone to look.
Codes this can cause (11)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0540 Intake Air Heater A Circuit Likely for this code Low
- P0541 Intake Air Heater A Circuit Low Likely for this code Low
- P0640 Intake Air Heater Control Circuit Likely for this code Low
- P2604 Intake Air Heater A Circuit Range/Performance Likely for this code Moderate
- P2605 Intake Air Heater B Circuit/Open Likely for this code Moderate
- P2606 Intake Air Heater B Circuit Range/Performance Likely for this code Moderate
- P2607 Intake Air Heater B Circuit Low Likely for this code Moderate
- P2609 Intake Air Heater System Performance Likely for this code Moderate
- P0542 Intake Air Heater A Circuit High Low
- P0543 Intake Air Heater A Circuit Open Low
- P2608 Intake Air Heater B Circuit High Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Others who found this
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about Failed intake air heater relay.