What does code P2B77 mean?

Q: What does code P2B77 mean?

Coolant Heater B Control Circuit Low. P2B77 indicates that the powertrain control module has detected an abnormally low voltage or current on the control circuit for coolant heater B, which is typically a supplemental electric heater used to warm the engine coolant or passenger compartment quickly. The computer expects a certain signal or current draw when the heater is commanded on, but the circuit is showing a low condition that falls outside the expected range.

DTC codes / P2Bxx · Hybrid propulsion / P2B77

P2B77Coolant Heater B Control Circuit Low

P2B77 indicates that the powertrain control module has detected an abnormally low voltage or current on the control circuit for coolant heater B, which is typically a supplemental electric heater used to warm the engine coolant or passenger compartment quickly. The computer expects a certain signal or current draw when the heater is commanded on, but the circuit is showing a low condition that falls outside the expected range.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.