What it means
The intake air heater B circuit is not performing as expected. The code identifies a circuit or system performance fault; it does not by itself establish that the heater grid or relay has a particular resistance fault.
At a glance
- Usually lights the check-engine light
How it works
Intake air heater B is the secondary heater circuit that helps warm air entering a diesel engine during cold starts. The controller assesses whether circuit B performs as expected when commanded; P2606 reports a performance mismatch without identifying a particular resistance or failed part. A cold engine may crank longer, run roughly, or produce more smoke if the heater is not providing enough heat.
Common causes
Most likely first.
- Faulty intake air heater element
- Faulty relay or wiring
Symptoms
- Check-engine light
- Longer cranking or hard starting in cold weather
- Rough running or increased exhaust smoke after a cold start
How to diagnose it
- Record freeze-frame data and compare coolant and intake-air temperatures with ambient conditions to see whether the fault occurred during a cold-start heater demand.
- Inspect heater grid B, its relay, connectors, and wiring for damage, looseness, or corrosion.
- Use scan-tool data or the manufacturer's test procedure to confirm whether heater B is being commanded and whether its operation matches expectations.
- Check the heater element and relay for continuity and operation using the manufacturer's procedures.
- Measure the heater B circuit for excessive voltage drop or poor connections under the commanded load, following manufacturer guidance.
Common fixes
- Clean and secure corroded or loose heater B connections.
- Repair damaged wiring in the heater B circuit.
- Replace the faulty heater B relay.
- Replace the heater B element if testing confirms it is faulty.
Can I keep driving?
The vehicle may be drivable if it runs normally, but cold starts can become harder and may produce extra smoke. Limit use in cold weather until heater B performance is restored.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.