OBD Guide

P2B77

Coolant Heater B Control Circuit Low

P2B77 is an OBD-II diagnostic trouble code meaning: Coolant Heater B Control Circuit Low. Common causes: coolant heater malfunction, open or short circuit in control circuit. Estimated repair cost: $17–56.

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

  1. Check heater circuit fuses and relays
  2. Inspect the wiring harness for damage
  3. Check heater resistance
  4. Diagnose the engine control unit
  5. Replace coolant heater if necessary

Related codes

Error P2B77 by Vehicle Brand

FAQ

What does the P2B77 code mean?

P2B77 is an OBD-II diagnostic trouble code that indicates: Coolant Heater B Control Circuit Low

What causes a P2B77 error code?

The most common causes of P2B77 include: Coolant heater malfunction; Open or short circuit in control circuit; Relay or fuse problems; Engine control unit malfunction.

How do I fix a P2B77 diagnostic trouble code?

To fix P2B77: Check heater circuit fuses and relays. Inspect the wiring harness for damage. Check heater resistance. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P2B77?

Yes, but get it checked soon

How much does it cost to fix P2B77?

The estimated repair cost for P2B77 is $17–56. Actual cost depends on your vehicle, location, and labor rates.

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