P0145: O2 Sensor Circuit Slow Response (Bank 1, Sensor 3)

P0145 means the third oxygen sensor on Bank 1 (typically placed after a second catalyst stage or in commercial vehicle aftertreatment systems) is not switching between rich and lean readings quickly enough during the ECU's monitor test. This code applies primarily to specific engine configurations with three sensors per bank, common on diesel commercial vehicles and some V6/V8 multi-converter setups.

P0145 is a emissions-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0145 and illuminates the check engine light.

If your vehicle has triggered P0145, you may notice one or more of these symptoms:

• Check engine light illuminated
• Slight reduction in fuel economy
• Possible failed emissions test
• No noticeable driveability symptoms
• May appear with P0420 if the aftertreatment is also degrading

Here are the most common causes of P0145, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. Safe to drive short term. A slow Sensor 3 distorts the aftertreatment monitoring strategy, so a developing catalyst or SCR problem may be masked. Plan a repair within a few weeks to keep emissions diagnostics working properly.

Follow these steps to pinpoint the root cause of P0145:

1. Confirm the vehicle's exhaust layout. Sensor 3 is rare and only present on multi-catalyst configurations or diesel commercials with extended aftertreatment
2. Read freeze frame data and look for companion codes (P0420, P0143) that suggest a broader aftertreatment issue
3. Inspect the exhaust system around Sensor 3 for leaks that could distort the gas sample
4. Use a scan tool to graph Sensor 3 voltage during steady cruise and deceleration fuel cut. A healthy sensor reacts within roughly 100 ms to a lean spike when fuel is cut
5. Substitute a known-good sensor. Response time is the only definitive test, so if the new sensor responds correctly, the original was aged out

Repair costs for P0145 vary depending on the root cause and your vehicle. Here are typical estimates:

P0145 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0145 or indicate related issues: