P2604Intake Air Heater A Circuit Range/Performance
- 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
- P2604 is the functional check of intake air heater A - the grid heater in the intake that warms the charge air of a diesel engine for cold starts. The circuit responds, but current, voltage drop or heating effect do not match the command. Under CARB, a glow plug or intake air heater has to be checked both for reacting correctly when commanded and for plausible current and voltage drop in its circuit. Volvo's heavy-truck engine bulletins (2020, 2022) list P2604-7F among the codes caused by a weak pre-heat relay and fix it with a software update, a check of terminal tension at heater and relay, and a new relay plus supply cable. P0540-P0543 cover the electrical faults of heater A, P2605-P2608 heater B, P2609 the system. Expect hard cold starts and white smoke.
- What you may notice
- Hard starting in cold weather
- White smoke and rough running after a cold start
- Check engine light
- Likely causes
- LikelyWorn or sticking intake air heater relay
- PossibleLoose or burnt terminals on the heater supply cable
- PossibleDegraded or partly open heater grid
- RareOutdated engine software (manufacturer update available)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.