Technical Description of OBD-II Trouble Code
Correlation between Radiator Coolant Temperature and Engine Coolant Temperature
What does that signify?
This generic powertrain diagnostic trouble code (DTC) is commonly found in many OBD-II vehicles, particularly Chevrolet/Chevy and Vauxhall vehicles.
Whenever a code P00B6 is diagnosed, it indicates that the powertrain control module (PCM) has detected a discrepancy in the signals between the radiator coolant temperature sensor and the engine coolant temperature (ECT) sensor.
To ensure that coolant is flowing properly between the radiator and the engine cooling passages, the temperature of the coolant in the radiator is compared to the temperature of the coolant in the engine.
The ECT sensor is typically made of a thermal resistor that is sealed in a metal or plastic housing. Brass is commonly used for the housing due to its durability. The ECT sensor is usually threaded and installed in a coolant passage in the engine intake manifold, cylinder head, or block. As the coolant warms and flows across the sensor, the thermal resistance decreases, resulting in increased circuit voltage at the PCM. Conversely, as the engine cools, the sensor resistance increases, leading to a reduction in circuit voltage to the PCM. The PCM interprets these voltage fluctuations as changes in engine coolant temperature, which affects fuel delivery and ignition timing strategy.
The radiator coolant temperature sensor functions similarly to the ECT sensor, monitoring coolant temperature in the radiator or coolant reservoir.
If the PCM detects voltage signals from the ECT sensor and the radiator coolant temperature sensor that differ by more than the maximum allowable parameter, a code P00B6 is stored and the malfunction indicator lamp (MIL) may illuminate. Multiple drive cycles with a failure may be required for MIL illumination.
An example of a radiator coolant temperature sensor:
What is the severity of this DTC?
Addressing the conditions that contribute to a stored code P00B6 is crucial as the ECT sensor input is vital for fuel delivery and ignition timing strategy.
What are some of the symptoms of the code?
Symptoms of a P00B6 engine code may include:
What are some of the common causes of the code?
Possible causes for this engine code may include:
What are some P00B6 troubleshooting steps?
Prior to diagnosing any stored ECT sensor related codes, it is important to ensure that the engine is filled with coolant and not overheating. The engine must be full of the proper coolant and not overheating under any circumstances.
To diagnose a code P00B6, you will need a reliable source of vehicle information, a diagnostic scanner, a digital volt/ohmmeter (DVOM), and an infrared thermometer with a laser pointer.
If the engine is not overheating, the next step is to visually inspect the wiring and connectors of the ECT sensor and radiator coolant temperature sensor system.
Connect the scanner to the vehicle diagnostic port to retrieve all stored codes and freeze frame data. Write down this information as it may be helpful during the diagnosis. Clear the codes and test-drive the vehicle to see if the code is reset.
Refer to your vehicle information source for wiring diagrams, connector pin-out charts, component testing specifications, and connector views. These resources will assist you in testing individual circuits and sensors using the DVOM. It is important to test individual system circuits only after disconnecting the PCM and all related controllers to prevent controller damage. Connector pin-out charts and wiring diagrams are particularly useful for testing circuit voltage, resistance, and continuity.
How to test the radiator coolant temperature sensor and the ECT sensor:
How to probe for reference voltage and ground at the radiator coolant temperature sensor and ECT sensor:
How to test radiator coolant temperature sensor and ECT sensor signal voltage:
If the individual sensor signal circuits reflect the correct degree of voltage at the sensor connector, test the individual signal circuits at the PCM connector using the DVOM. If the sensor signal detected at the sensor connector is not present at the corresponding circuit of the PCM connector, there is an open circuit between the sensor and the PCM.
Only after exhausting all other possibilities, and if all radiator coolant temperature and ECT temperature sensors and circuits are within specifications, should you suspect PCM failure or a PCM programming error.
