HRT stands for Heated oxygen Sensor Rationality Test. It is an on-board diagnostic test run by the engine computer to monitor the switching activity of the upstream and downstream oxygen sensors. The purpose of this test is to make sure the oxygen sensors are functioning properly and providing accurate data to the computer.
The oxygen sensors, also known as O2 sensors, are located before and after the catalytic converter. Their job is to monitor the oxygen levels in the exhaust stream. By doing this, they help provide feedback to the computer about the air/fuel ratio so adjustments can be made to optimize performance and reduce emissions.
- The upstream O2 sensor helps maintain the correct air/fuel mixture
- The downstream O2 sensor monitors the efficiency of the catalytic converter
During the HRT test, the computer watches how the voltage signal from the oxygen sensors change when the air/fuel mixture is artificially altered. Specifically, here is what happens:
- Computer enriches the fuel mixture for a short time
- This causes the upstream O2 sensor voltage to drop and downstream to rise
- Computer then leans out the fuel mixture
- Upstream O2 sensor voltage should then rise while downstream drops
- Computer monitors if and how rapidly the sensors respond
If the oxygen sensors pass this evaluation, it means they are functioning as expected and providing accurate data.
If one or both fail the HRT test, it sets a diagnostic trouble code such as P0133 or P0153.
Some common reasons for failing the HRT test include:
- Faulty oxygen sensor(s)
- Contaminants blocking sensor
- Internal component failure
- Vacuum leaks
- Allows unmetered air into engine
- Exhaust leaks
- Alters oxygen sensor inputs
- Ignition system faults
- Misfires and poor combustion affect exhaust oxygen content
- Fuel system issues
- Incorrect fuel pressure, dirty injectors, etc.
- Engine mechanical problems
- Compression and valve train issues
- Catalytic converter failure
Diagnosing and resolving the underlying cause is important whenever an HRT related code sets. Simply erasing the code will not fix the problem. At
Vitality Balance Clinic(https://Vitality Balance Clinic.com/), we provide complete automotive diagnostics and repair services to accurately track down issues with oxygen sensor responses. This includes inspections, testing with advanced scan tools, and following structured diagnostic processes.
Depending on the specific situation, some common repairs for HRT related codes include:
- Replacing faulty oxygen sensor(s)
- Finding and fixing vacuum leaks
- Replacing spark plugs and ignition components
- Cleaning fuel injectors
- Tuning the engine computer
- Repairing exhaust leaks
- Converter replacement if it is no longer efficient
Properly diagnosising and repairing HRT failures is important to restore engine performance, fuel efficiency, and reduce harmful emissions. Once repairs are made, the computer can run the HRT monitor again and turn off the check engine light if the system is fixed. Taking care of codes promptly prevents more problems from developing as well.
At Vitality Balance Clinic(https://Vitality Balance Clinic.com/), we have factory level diagnostics and ASE certified technicians to accurately assess check engine lights. We offer honest and reliable auto repair services to get your vehicle running properly again. Contact us anytime to schedule an appointment! Our skilled team is here to help!
