P2606 code meaning
Intake Air Heater B Circuit Range/Performance
Powertrain system Generic code P26xx codes Check engine light
What P2606 means
P2606 means heater B in the intake does respond, but the current it draws or the voltage drop across its circuit lies outside the window the engine controller expects. Mack documents P2604-7F and P2606-7F for 2014-2017 trucks with MP7, MP8 and MP10 engines and puts them down to extra circuit resistance from corrosion inside the master disconnect switch, so inspecting those contacts comes first. Volvo's 2020 software change log for heavy-truck engines lists P2606-7F next to the heater A code as a result of the preheater relay issue addressed by new EMS software. Unlike P2605, P2607 and P2608, the circuit is not open or shorted but merely implausible; P2604 is the same check for heater A. Cold starts may become sluggish and the engine may smoke white until warm.
P2606 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P2606
- Sluggish cold starts
- White smoke until the engine is warm
- MIL on
Common causes of P2606
- Most likelyExtra resistance from corroded contacts, e.g. in the master disconnect switch
- PossibleWorn preheat relay contacts
- PossibleAged heater element with changed resistance
- Less likelyOutdated engine software (update published by the maker)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Intake air heater bHeater relay
What each part of P2606 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 6 | Area: computer (engine control module) and output circuits. |
| 06 | The exact fault in that area. |
What to do next
- Note P2606 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2606
What does P2606 mean?
P2606 means "Intake Air Heater B Circuit Range/Performance". P2606 means heater B in the intake does respond, but the current it draws or the voltage drop across its circuit lies outside the window the engine controller expects. It is a generic code, so it means the same on every make.
Is it safe to drive with P2606?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2606 fail an emissions test?
Yes, it can. P2606 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2606 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P2606 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.