P00B3 Low Radiator Coolant Temperature Sensor Circuit

P00B3 Low Radiator Coolant Temperature Sensor Circuit

OBD-II DTC Datasheet

Low signal level in the radiator coolant temperature sensor circuit

What does this mean?

This Generic Transmission Diagnostic Trouble Code (DTC) typically applies to all OBD-II vehicles. This may include, but is not limited to, Mercedes, Vauxhall, Nissan, BMW, Mini, Chevy, Mazda, Honda, Acura, Ford, etc.

The cooling system is an integral part of your vehicle's engine system. It is responsible not only for controlling the temperature of your engine, but also for regulating it. Various electrical and mechanical systems / components are used for this, including but not limited to: coolant temperature sensor (CTS), radiator, water pump, thermostat, etc.

The engine control module (ECM) uses CTS values ​​to monitor the engine temperature and, in turn, can fine tune it. Different temperatures require different air / fuel mixtures, so it is imperative that the CTS operates within the desired ranges. In most cases, CTSs are NTC sensors, which means that the resistance inside the sensor itself decreases as the temperature rises. Understanding this will help you a lot when troubleshooting.

The ECM activates P00B1 and related codes when it monitors one or more conditions outside a specified electrical range in the CTS or its circuit. The ECM may detect an inconsistent problem that comes and goes (P00B5). In my experience, the culprit here is usually mechanical. Be aware that electrical problems can also be the cause.

P00B3 A low radiator coolant temperature sensor circuit code is set when the ECM monitors a low specific electrical value in or in the radiator CTS. It is one of five related codes: P00B1, P00B2, P00B3, P00B4, and P00B5.

What is the severity of this DTC?

This code will be considered a moderately severe problem. This will depend on what symptoms you have and how the malfunction actually affects the performance of your vehicle. The fact that the functionality of the CTS directly affects the engine's air / fuel mixture makes this problem undesirable. If you neglect this problem long enough, you can run into huge engine repair bills.

Example of a radiator coolant temperature sensor:

What are some of the symptoms of the code?

Symptoms of the P00B3 diagnostic code may include:

• Hard cold start
• Unstable idle
• Engine stalls
• Poor fuel consumption
• Smoking exhaust
• Fuel odor Symptoms
• Erroneous or false temperature readings
• Poor engine performance

What are some of the common causes for the code?

Reasons for this code may include:

• Defective radiator or other coolant temperature sensor (CTS)
• Dirty / clogged sensor sensor
• Leaking o-ring / sensor gasket
• Broken or damaged wire harness
• fuse
• ECM problem
• Contact / connector problem (corrosion, melting, broken retainer, etc.)

What are some steps to troubleshoot the P00B3?

Be sure to check the Technical Service Bulletins (TSB) for your vehicle. Gaining access to a known fix can save you time and money during diagnostics.

Tools

Some of the things you may need when diagnosing or repairing radiator coolant temperature sensor circuits and systems are:

• OBD code reader
• Antifreeze / coolant
• Pallet
• multimeter
• Basic set of sockets
• Basic Ratchet and Wrench Sets
• Basic screwdriver set
• Battery terminal cleaner
• Service manual

Security

• Let the engine cool down
• Chalk circles
• Wear PPE (Personal Protective Equipment)

NOTE. ALWAYS check and record the integrity of the battery and charging system before further troubleshooting.

Basic step # 1

If this code is set, the first thing I would do would be to check the radiator coolant temperature sensor itself for any obvious signs of damage. Generally speaking, these sensors are installed in the radiator or somewhere along the coolant line / hoses, but I've also seen them installed on the cylinder head itself among other obscure places, so see your service manual for the exact location.

NOTE: Whenever you diagnose / repair anything related to the cooling system, be sure to let the engine cool completely before proceeding.

Basic step # 2

Check the sensor. Given the fact that the internal resistance within the sensor changes with temperature, you will need the specific resistance / temperature desired (see manual). After obtaining the specifications, use a multimeter to check the resistance between the contacts of the CTS heatsink. Anything outside the desired range indicates a faulty sensor. Replace if necessary.

NOTE. Over time and under the influence of the elements, the plastic of these sensors can become very fragile. Be careful not to damage the connectors during diagnosis / repair.

Basic tip # 3

Check for leaks. Make sure the sensor does not leak around its seal. Leakage here can lead to erroneous readings as air enters the system. For the most part, these gaskets / seals are extremely easy to replace and inexpensive. Regardless of whether this is actually the root cause of your problem, it needs to be addressed before proceeding.

NOTE: Refer to your service manual for the exact antifreeze / coolant to use. Using the wrong antifreeze can cause internal corrosion, so be sure to buy the right product!

Basic step # 4

Given the location of the sensor, pay particular attention to where the CTS harness is routed. These sensors and the associated harness are subject to intense heat, not to mention the elements. Melting wire harness and wire harness is a common cause of these problems, so repair any damaged wiring.

Basic step # 5

Clear CTS. You can simply remove the sensor completely from the vehicle. If so, you can remove the sensor and check for debris / debris that could affect the sensor's ability to get correct readings.

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