Powertrain
Definition only
Lights the check engine lamp
P2B77: Coolant Heater B Control Circuit Low
Standardized SAE J2012 code · P2Bxx codes
What does P2B77 mean?
The control circuit of coolant heater B reports a control circuit low condition. Auxiliary preheating of the coolant cannot be commanded as expected.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Common causes
- High Control wire shorted to ground
- Medium Heater element shorted
- Low Connector pins corroded - high contact resistance
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of P2B77 on the same make and model first.
P2B77 in the community
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