P2B77

Coolant Heater B Control Circuit Low

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$17–56 (est.)

Symptoms

Extended engine warm-up time
Decrease in interior heating efficiency
Check Engine Light Illuminates
Unstable engine operation at idle

Causes

Coolant heater malfunction
Open or short circuit in control circuit
Relay or fuse problems
Engine control unit malfunction
Poor contact in circuit connectors

How to Fix

Check heater circuit fuses and relays
Inspect the wiring harness for damage
Check heater resistance
Diagnose the engine control unit
Replace coolant heater if necessary

Related codes

P2B76 P2B78 P2B79