Radiator Coolant Temperature Sensor Circuit Low
The P00B3 code indicates that the Engine Control Module (ECM) has detected a low voltage signal from the radiator coolant temperature sensor circuit. This sensor monitors the coolant temperature at the radiator outlet. A low voltage reading typically means the sensor is reading an abnormally high temperature or there is a short to ground in the circuit. This can lead to incorrect cooling fan operation, poor fuel economy, and potential engine overheating if not addressed.
01. Most Common Causes
- Faulty radiator coolant temperature sensor
- Short to ground in the sensor wiring or connector
- Open circuit in the sensor signal wire
- Corroded or damaged sensor connector
- Failed ECM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine cooling fans running constantly or not at all
- Poor fuel economy
- Engine overheating or running cooler than normal
- Hard starting or rough idle
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the radiator coolant temperature sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Disconnect the sensor and measure its resistance with a multimeter; compare to manufacturer specifications at various temperatures.
Step 4: Check for voltage and ground at the sensor connector with the ignition on; should be around 5V reference and good ground.
Step 5: If sensor and wiring are okay, test the ECM by checking continuity from the sensor connector to the ECM.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause the engine to overheat or run inefficiently, potentially leading to serious engine damage.
How much does it cost to fix?▼
The cost to fix P00B3 typically ranges from $50 to $150, including parts (sensor) and labor. Diagnostic fees may be additional.