P0145
O2 Sensor Circuit Slow Response (Bank 1, Sensor 3)
What could P0145 mean for your vehicle?
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The P0145 code means the PCM has determined that the third oxygen sensor on Bank 1 is responding too slowly to changes in exhaust gas oxygen content. The PCM monitors how quickly the sensor switches between rich and lean voltage readings and sets this code when the response time exceeds acceptable limits.
This sensor sits after a secondary catalytic converter on Bank 1 and is used primarily for emissions monitoring. A slow response from this sensor won't typically cause noticeable performance issues, but it will keep the check engine light illuminated and cause an emissions test failure.
The most common cause is simply an aging sensor that needs replacement. O2 sensors are wear items that degrade over tens of thousands of miles. Before replacing the sensor, visually inspect the wiring and connector for heat damage or corrosion, and check for exhaust leaks near the sensor mounting location. If the code persists after sensor replacement, have the secondary catalytic converter inspected, as its deterioration can produce exhaust conditions that affect sensor readings.
Severity
Symptoms
- •Check engine light is on
- •Vehicle fails emissions testing
- •Slight decrease in fuel economy
- •No significant drivability issues
- •Possible faint unusual exhaust odor
Likely Causes
Over time and miles, the sensing element becomes sluggish and cannot switch between rich and lean readings at the speed the PCM expects.
An exhaust leak allows outside air to dilute the exhaust gases reaching the sensor, causing it to respond more slowly or erratically.
Corroded, frayed, or heat-damaged wiring can cause intermittent signal delays that mimic a slow sensor response.
A degrading secondary catalytic converter can alter the exhaust gas composition in ways that cause the downstream sensor to appear sluggish.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the O2 sensor (Bank 1, Sensor 3)
- Repair exhaust leaks near the sensor
- Repair or replace corroded wiring and connectors
- Inspect secondary catalytic converter for deterioration
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