P2B76: Coolant Heater B Control Circuit/Open

What it means

The control circuit of coolant heater B reports a control circuit/open condition. Auxiliary preheating of the coolant cannot be commanded as expected.

At a glance

• Usually lights the check-engine light

How it works

Coolant heater B is an electrically controlled element that helps warm coolant before the engine generates much heat. The control module monitors heater B's circuit response and sets P2B76 when that circuit appears open, preventing expected auxiliary preheating.

Common causes

Most likely first.

1. Open in heater control wire
2. Open heater element
3. Pin pushed back out of connector body

Symptoms

• Check-engine light
• Coolant or engine may take longer to warm up
• Cabin heat may take longer to become warm

How to diagnose it

1. Check freeze-frame data and heater commands to confirm when the fault occurred and whether heater B was requested.
2. With the system off and cool, inspect heater B's connector for a backed-out pin, corrosion, looseness, or damaged wiring.
3. Check the heater B control wire for continuity between the specified terminals, following the manufacturer's wiring information.
4. Test heater B's element for an open circuit using the manufacturer's procedure and specification.
5. If the wiring, connector, and element pass, check the control module's output and circuit monitoring against the manufacturer's procedure.

Common fixes

• Reseat a pushed-back heater B connector pin and secure the connector.
• Repair an open or damaged heater B control wire.
• Clean or repair a poor heater B connector connection.
• Replace the heater B element if it tests open.

Can I keep driving?

The engine can generally be driven if its normal temperature stays stable, but heater B may not preheat the coolant, delaying engine warm-up and cabin heat. Avoid relying on quick cabin heat in cold weather, and stop if the engine overheats.