Low coolant level or air trapped in the cooling system; Faulty or slow-to-respond coolant pump (mechanical or electric); Thermostat stuck closed or open, or an electronically controlled thermostat not responding; Faulty coolant temperature sensor or its wiring and connector giving implausible readings; Blocked radiator, heater matrix or collapsed hose restricting flow; Faulty coolant control valve or auxiliary pump circuit, on engines that have them; Internal engine or head gasket fault allowing gas into the coolant and disrupting flow.

P00B7

Engine Coolant Flow Low/Performance.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
B7: FaultThe specific fault in that area

What it means

P00B7 is the generic code for engine coolant flow low or performance. The engine control unit has judged that coolant is not circulating as well as it expects, based on temperature readings and how quickly the engine warms up or responds to cooling demand. Exact monitoring strategy varies by manufacturer and engine, so the precise trigger conditions depend on the model.

Symptoms

Engine temperature warning light or gauge reading high
Engine running hotter than normal or slow to warm up
Poor or no heater output in the cabin
Reduced power or limp mode in some vehicles
Cooling fans running constantly or more than usual
Coolant loss or low coolant level warning

Possible causes

Low coolant level or air trapped in the cooling systemlikely
Faulty or slow-to-respond coolant pump (mechanical or electric)likely
Thermostat stuck closed or open, or an electronically controlled thermostat not respondinglikely
Faulty coolant temperature sensor or its wiring and connector giving implausible readingspossible
Blocked radiator, heater matrix or collapsed hose restricting flowpossible
Faulty coolant control valve or auxiliary pump circuit, on engines that have thempossible
Internal engine or head gasket fault allowing gas into the coolant and disrupting flowrare

How to diagnose

Read stored and pending codes and freeze frame data, noting coolant temperature, engine load and speed when the code set
Check the coolant level cold and inspect for leaks, staining and a pressure-cap that seals properly
Inspect the coolant temperature sensor wiring and connectors for damage, corrosion or looseness
Compare live coolant temperature against a trusted reading such as an infrared thermometer on the hoses, and check it rises smoothly
With the engine warm, feel the radiator hoses and check the thermostat opens and flow is present, following the manufacturer procedure
Check the coolant pump operation, belt drive or electric pump command and supply, depending on the model
Look for signs of blockage by checking radiator temperature across its face and heater output
Test for combustion gas in the coolant if overheating or unexplained coolant loss is present

How to fix

Top up with the correct coolant type, repair any leaks and bleed air from the system as per the manufacturer procedure
Replace the coolant pump or repair its electrical supply and control circuit if it is faulty
Replace a stuck or slow thermostat or its electronic control
Repair wiring or replace the coolant temperature sensor if readings are implausible
Flush or replace a blocked radiator or heater matrix and renew any collapsed hoses
Replace a faulty coolant control valve, and repair the underlying engine fault if gas is entering the coolant

Can I keep driving?

High severity

Avoid driving if the temperature gauge is high, a warning is lit or coolant is low, as overheating can quickly cause severe engine damage. If the car is behaving normally and the level is correct, only drive a short distance to get it checked promptly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.