Technical Description of OBD-II Trouble Code
Intermittent Circuit Issue with Radiator Coolant Temperature Sensor
What does that signify?
This generic powertrain diagnostic trouble code (DTC) is applicable to all OBD-II vehicles, including but not limited to Mercedes, Vauxhall, Nissan, BMW, Mini, Chevy, Mazda, Honda, Acura, Ford, etc.
The cooling system is an essential component of your vehicle’s engine system. It is responsible for monitoring and regulating the engine’s temperature. This is achieved through various electrical and mechanical systems/components such as the Coolant Temperature Sensor (CTS), radiator, water pump, thermostat, etc.
The Engine Control Module (ECM) utilizes the values from the CTS to accurately monitor and regulate the engine’s temperature. Different temperatures require different air/fuel mixtures, so it is crucial for the CTS to function within the desired ranges. In most cases, CTSs are Negative Temperature Coefficient sensors, meaning that the resistance within the sensor decreases as the temperature rises. Understanding this concept is beneficial for troubleshooting purposes.
The ECM triggers the P00B1 code and associated codes when it detects one or multiple conditions outside the specific electrical range within the CTS or its circuit. The ECM may identify an intermittent issue (P00B5) that occurs sporadically. From my experience, the main cause of this issue tends to be mechanical, although electrical faults could also be responsible.
The P00B5 Radiator Coolant Temperature Sensor Circuit Intermittent code is set when the ECM detects an intermittent malfunction within the CTS or its circuit. It is one of five related codes, which are P00B1, P00B2, P00B3, P00B4, and P00B5.
What is the severity of this DTC?
This code is considered moderately severe. The severity may vary depending on the symptoms and how the fault affects the vehicle’s performance. Since the functionality of the CTS directly influences the engine’s air/fuel mixture, it is crucial to address this issue promptly. Neglecting this problem for an extended period could result in expensive engine repairs.
An example of a radiator coolant temperature sensor:
What are some of the symptoms of the code?
Symptoms associated with the P00B5 diagnostic code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P00B5 troubleshooting steps?
It is advisable to check for any technical service bulletins (TSBs) related to your vehicle. Accessing a known fix can save time and money during the diagnosis process.
Tools
The following tools may be necessary when diagnosing or repairing the radiator coolant temperature sensor circuits and systems:
Safety Tips
NOTE: ALWAYS verify and record the integrity of your battery and charging system before proceeding with further troubleshooting.
Basic Step #1
If this code is set, the first step would be to inspect the radiator coolant temperature sensor for any visible signs of damage. Typically, these sensors are mounted in the radiator or along the coolant lines/hoses. However, they can also be found mounted to the cylinder head or other obscure locations. Refer to your service manual for the exact location.
NOTE: When diagnosing or repairing anything related to the cooling system, ensure that the engine has completely cooled down before proceeding.
Basic Step #2
Test the sensor. Since the internal resistance within the sensor changes with temperature, you will need to determine the desired resistance/temperature (refer to the manual). Using a multimeter, measure the resistance between the pins of the radiator CTS. Any reading outside the desired range indicates a defective sensor. Replace it if necessary.
NOTE: Over time and exposure to the elements, the plastic housing of these sensors can become brittle. Be careful not to damage the connectors during diagnosis or repair.
Basic Tip #3
Check for leaks. Ensure that the sensor is not leaking around its seal. A leak in this area can cause erratic readings as air enters the system. In most cases, replacing the gaskets/seals is a simple and inexpensive solution. Regardless of whether this is the root cause of the problem or not, it should be addressed before proceeding.
NOTE: Refer to your service manual to determine the specific antifreeze/coolant to be used. Using the incorrect type of antifreeze can lead to internal corrosion, so make sure to use the appropriate product.
Basic Step #4
Pay special attention to the routing of the CTS harness, considering its location. These sensors and their corresponding harnesses are exposed to extreme heat and the elements. Melting harnesses and wires are common issues in these cases, so repair any damaged wiring.
Basic Step #5
Clean the CTS. If possible, remove the sensor from the vehicle to inspect for any debris or residue that may affect its ability to provide accurate readings.
