Powertrain, generic (extended)

P2B76 Coolant Heater B Control Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2B76 reports an open command circuit for coolant heater B. Where a vehicle has two separately requested heaters or heating stages – Hyundai and Kia patent US11378000B2 describes one housing with several sheath elements that a controller switches individually – B stands for the second channel. Which physical heater carries the letter is up to the manufacturer, and none documents P2B76 publicly. Typical findings are a terminal pushed out of the connector, a wire broken where the harness flexes near the heater, or a blown feed for the request line. California's OBD rule covers outputs of this kind with a circuit test. Heater A often keeps working, so heating is only weaker; if both fail, look at P2B72 and the communication code U069E too.

Likely causes

Request wire for heater B broken at a flex point
Terminal pushed out of the heater connector
Fuse feeding the request circuit blown
Heater B input open inside the heater electronics

Symptoms

  • Reduced heating power, cabin warms more slowly
  • Defrosting takes longer in cold weather
  • Fault entry often without other noticeable effects

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time0.5–3 h

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

Parts involved

coolant heater bwiring harnessecm

Related codes

P2B77P2B78P2B79P2B72P01EC

References: law.cornell.edu, patents.google.com, static.nhtsa.gov.