P00B1 - Radiator Coolant Temperature Sensor 2 Circuit High
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P00B1 is triggered when the Engine Control Unit (ECU) detects a voltage signal from the Radiator Coolant Temperature Sensor 2 (ECT 2) that is higher than the calibrated threshold (typically above 4.8V-4.9V). This sensor is usually located at the radiator outlet or lower radiator hose. The ECU utilizes ECT 2 to monitor thermostat efficiency and radiator performance. A 'Circuit High' condition typically signifies an open circuit (break in wiring) or a disconnected sensor, leading to infinite resistance and maximum signal voltage.
Possible Causes
Faulty Radiator Coolant Temperature Sensor (ECT 2) with internal open circuit
Connector issues or corrosion at the sensor pins
Wiring harness break in signal or ground return line
Faulty Engine Control Unit (ECU)
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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