Powertrain, generic (extended)

P2608 Intake Air Heater B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2608 is logged when the circuit of intake air heater B reads too high, for instance a short to battery positive on the control line or a relay that stays energized when it should be off. Volvo is the one maker that names it in public bulletins: the August 2020 EMS change log for heavy-truck engines lists P2608-00 among the preheater codes reduced by a relay robustness update, and Volvo's 2022 instruction for the pre-heat relay on 11 L and 13 L engines includes P2608-7E in its scope before replacing relay and supply cable. Deutz uses P0542 with the same meaning for its preheating relay. A heater stuck on drains the batteries and can overheat cables; a dead heater makes cold starts hard. P2607 is the low-side code, P2605 the open circuit.

Likely causes

Preheat relay contacts welded or sticking closed
Control or feedback wire shorted to battery positive
Engine software needing the maker's update

Symptoms

  • MIL on
  • Batteries run down after short trips or standstill
  • Hard cold starts or white smoke

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–700
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

intake air heater bheater relaywiring harness

Related codes

P2605P2606P2607P0542P2CE4

References: static.nhtsa.gov, static.nhtsa.gov, serdia.deutz.com.