Powertrain, generic · Fuel and air metering, auxiliary emission controls
P00B7 Engine Coolant Flow Low/Performance
Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo
When the engine is hot, the thermostat should be open and coolant should flow through the radiator. P00B7 is set when the engine coolant temperature is very high (above about 117 to 119 °C in documented cases) while the radiator side stays much colder, so too little coolant flows through the radiator. The usual cause is a thermostat stuck closed; low coolant, air in the system, a pump that delivers too little or a blocked radiator have the same effect. If the temperature keeps rising, stop driving to avoid engine damage.
Likely causes
Thermostat stuck closed
Low coolant level or air in the cooling system
Coolant pump delivering too little (impeller, drive; known cases on some engines)
Radiator or hoses blocked
One of the temperature sensors reading wrong
Symptoms
- Check engine light on
- Coolant warning light
- High engine temperature up to overheating
- Weak or fluctuating cabin heating
Repair estimate
DifficultyMediumDIY possible
Parts and labour€100–700
Time1–4 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
thermostatcoolant pumpradiatorengine coolantradiator coolant temperature sensor
Related codes
References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, techtips.ie.