OBD-II code · Powertrain (generic, extended)
P2B77 Coolant Heater B Control Circuit Low
The control circuit of coolant heater B reports a control circuit low condition. Auxiliary preheating of the coolant cannot be commanded as expected.
Is it safe to drive with P2B77?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyControl wire shorted to ground
- PossibleHeater element shorted
- Less likelyConnector pins corroded - high contact resistance
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Coolant Heater B, Wiring Harness, Ecm
Related codes
- P2B73Coolant Heater A Control Circuit Low
- P2B74Coolant Heater A Control Circuit High
- P2B75Coolant Heater A Control Circuit Performance
- P2B76Coolant Heater B Control Circuit/Open
- P2B78Coolant Heater B Control Circuit High
- P2B79Coolant Heater B Control Circuit Performance
- P2B7AEVAP System Pressure Sensor/Switch C Circuit
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.