OBD-II code P2605 indicates an open circuit in the intake air heater B circuit. This means the engine control module (PCM/ECM) has detected a break or discontinuity in the electrical path that controls the intake air heater, which is used to warm incoming air for better combustion, especially in cold conditions.
The relay responsible for supplying power to the intake air heater may have failed, causing an open circuit. Relays can wear out over time due to electrical load or corrosion.
Wiring harnesses or connectors in the intake air heater circuit may be damaged, corroded, or disconnected, leading to an open circuit. This is common in areas exposed to heat, vibration, or moisture.
A fuse protecting the intake air heater circuit may have blown due to a short or excessive current draw, resulting in an open circuit.
The heater element itself may have failed internally, creating an open circuit. This can occur due to age, thermal stress, or electrical overload.
Corrosion, loose terminals, or poor contact at the heater connector can cause an open circuit. This is often due to environmental exposure or vibration.
While uncommon, a malfunction in the engine control module could incorrectly report an open circuit in the intake air heater B circuit. This should only be considered after all other causes have been ruled out.
While it is technically possible for a faulty PCM/ECM to trigger P2605, it is extremely rare. The PCM/ECM should only be suspected as the cause after all other components, such as the relay, wiring, fuse, and heater element, have been thoroughly tested and ruled out.
Intake air heaters are used primarily in diesel engines and some gasoline engines to warm the incoming air during cold starts. This improves combustion efficiency, reduces emissions, and helps the engine start more easily in low temperatures.
Driving with P2605 may result in harder starts, rough idle, or reduced performance in cold weather. While the vehicle may still run, prolonged driving without addressing the issue could lead to increased emissions or difficulty starting in cold conditions.
In some vehicles, you may hear a relay click or feel warmth near the intake when the heater is activated (usually during cold starts). Alternatively, you can use a scan tool to monitor the heater's operation or test it with a multimeter for proper resistance and voltage.