Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's computer is confused about how hot or cold the engine is because it got a weird message.
The Engine Control Module (ECM) receives data about the engine's coolant temperature through the Controller Area Network (CAN). This code indicates that the data received is invalid or not within expected parameters.
The P173B code is set when the ECM detects an invalid or implausible signal from the Engine Coolant Temperature (ECT) sensor via the CAN bus. This could be due to a faulty sensor, wiring issues, or a problem with the CAN communication itself.
• Check Engine Light is on
• Engine overheating or running too cold
• Poor fuel economy
• Faulty Engine Coolant Temperature sensor
• Wiring issues or poor connections in the CAN bus
• Faulty ECM or CAN communication module
ECM: Engine Control Module
CAN: Controller Area Network
ECT: Engine Coolant Temperature
• Check for any other related trouble codes
• Inspect the ECT sensor and its wiring for damage
• Test the CAN bus communication for faults
• Replace the ECT sensor if faulty
• Repair or replace damaged wiring or connectors
• Reprogram or replace the ECM if necessary
• OBD-II scanner
• Multimeter
• CAN bus diagnostic tool
$100 - $500
Moderate
• Toyota Camry
• Honda Accord
• Ford Focus
• Regularly inspect and maintain the cooling system
• Ensure all electrical connections are secure
• Update vehicle software as recommended by the manufacturer
Sensor Issue
• Avoid driving the vehicle until the issue is resolved to prevent engine damage
• Consult a professional mechanic for accurate diagnosis
Check with your vehicle manufacturer for specific warranty coverage related to the ECM and sensors.
This code has been reported in vehicles with CAN bus communication issues, often related to faulty sensors or wiring problems.
Moderate – Addressing this issue promptly can prevent further engine damage.
Ignoring this code may lead to engine overheating, which can cause severe engine damage and pose safety risks.
• Engine at operating temperature
• Vehicle stationary
The ECT sensor is typically located near the thermostat housing on the engine block.
Q: Can I drive with a P173B code?
A: It's not recommended to drive with this code active, as it may lead to engine overheating.
Q: How do I clear a P173B code?
A: After repairs, use an OBD-II scanner to clear the code, but ensure the issue is resolved first.
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Universal · Digital multimeter
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Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
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Fitment Required · Vehicle-fitment part
Relevant when coolant-temperature and warm-up faults indicate a thermostat-related issue.
Coolant-temperature and warm-up faults often lead to thermostat testing and replacement.
Thermostats are vehicle-specific and should be matched by engine and housing style.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.