Powertrain, generic (extended)

P2BB6 Engine Coolant Temperature Sensor 6 Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2BB6 is the general circuit code for a sixth coolant temperature sensor, intended for control units that only know that the circuit is faulty and do not distinguish a grounded from an open or shorted-high line. Six or more coolant sensors appear on engines with split cooling, rotary coolant valves or separate branches for head, block, radiator and heater; which physical sensor gets number 6 is the manufacturer's decision. No manufacturer documents P2BB6 publicly. GM does read a sixth coolant channel in its 2019 and 2025 ECM tables, but reports its faults only through the specific codes P2BB8 and P2BB9. Under CARB rules each coolant temperature input must be tested for broken circuits and for readings beyond its plausible span. Unplugged connectors and broken leads are the likely reasons.

Likely causes

Sensor 6 connector unplugged, damaged or corroded
Open or shorted wire between sensor 6 and the ECM
Failed NTC element in sensor 6

Symptoms

  • MIL on
  • Sensor 6 shows a fixed substitute or implausible value
  • Fans may run continuously as a precaution

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–350
Time0.5–2.5 h

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

Parts involved

engine coolant temperature sensor 6wiring harnessecm

Related codes

P2BB7P2BB8P2BB9P2BBAP2B2BP2AFC

References: law.cornell.edu, gsi.ext.gm.com.