Severity High
P00B3

Radiator Coolant Temperature Sensor Circuit Low

📅 Last reviewed: July 2026
What does the P00B3 code mean?

The P00B3 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the radiator coolant temperature sensor that is lower than the expected range. This sensor monitors the coolant temperature at the radiator outlet, and a low voltage typically means the sensor is reading an extremely cold temperature or there is a short to ground in the circuit. This can cause the ECM to misinterpret coolant temperature, leading to improper engine cooling fan operation and potential overheating.

High
Severity
$50-$150
Typical Cost
High
Frequency

1. Most Common Causes

2. Symptoms You Will Notice

3. Step-by-Step Diagnosis

1

Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.

2

Step 2: Visually inspect the radiator coolant temperature sensor and its connector for damage, corrosion, or loose connections.

3

Step 3: Disconnect the sensor and measure its resistance with a multimeter; compare to manufacturer specifications at various temperatures.

4

Step 4: Check the sensor signal wire for a short to ground by disconnecting the ECM and measuring continuity to ground.

5

Step 5: If sensor and wiring are okay, test the ECM's ability to read the sensor by backprobing the signal wire with a known good sensor or scan tool data.

4. 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 and labor, depending on whether the sensor or wiring needs replacement.

5. Commonly Affected Makes

This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.

6. Related Codes

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