Ageing or worn oxygen sensor (Bank 1 Sensor 3) with a slow response; Sensor contaminated by oil, coolant, fuel additives or silicone; Exhaust leak near the sensor letting in air and distorting its reading; Damaged wiring, poor connector contact or corrosion in the sensor signal or earth circuit; Underlying engine fault such as misfire or a persistent fuel mixture problem affecting exhaust gas; Degraded catalytic converter altering the gas reaching the sensor; Fault in the engine control unit.

P0145

O2 Sensor Circuit Slow Response Bank 1 Sensor 3.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
45: FaultThe specific fault in that area

What it means

P0145 means the engine control unit judged the signal from the Bank 1 Sensor 3 oxygen sensor to be too slow in switching between rich and lean. Sensor 3 is fitted downstream of the first catalytic converter, and only on vehicles with a third oxygen sensor, usually after a second catalyst. The control unit compares how quickly the signal changes against what it expects during monitoring, and sets the code when the response is too sluggish. Sensor position and monitoring conditions vary by model and engine.

Symptoms

Engine warning light on
Usually no noticeable change in driving
Possible failed emissions test or monitor not completing
Occasionally slightly higher fuel consumption if other faults are present
Other stored codes for the same sensor, catalyst, fuel trim or misfire may accompany it

Possible causes

Ageing or worn oxygen sensor (Bank 1 Sensor 3) with a slow responselikely
Sensor contaminated by oil, coolant, fuel additives or siliconepossible
Exhaust leak near the sensor letting in air and distorting its readingpossible
Damaged wiring, poor connector contact or corrosion in the sensor signal or earth circuitpossible
Underlying engine fault such as misfire or a persistent fuel mixture problem affecting exhaust gaspossible
Degraded catalytic converter altering the gas reaching the sensorrare
Fault in the engine control unitrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, looking for related codes such as heater circuit, catalyst efficiency, misfire or fuel trim faults
Confirm where Bank 1 Sensor 3 is on this model and engine, as the layout varies
Visually inspect the sensor wiring and connector for heat damage, chafing, corrosion or water ingress
Inspect the exhaust from the manifold to the sensor for leaks, cracked joints or failed gaskets
Check short and long term fuel trims and look for misfires, oil or coolant consumption that could contaminate the sensor
Watch the sensor live data and see how quickly the signal reacts to a brief change in mixture, comparing with the other oxygen sensors and the model's specification
Check the sensor heater supply, earth and resistance against the manufacturer's figures
After repair, clear the codes and complete a drive cycle to confirm the monitor runs and passes

How to fix

Replace the Bank 1 Sensor 3 oxygen sensor if it is slow or contaminated
Repair or replace damaged wiring, terminals or connectors in the sensor circuit
Repair any exhaust leak near or ahead of the sensor
Correct any underlying misfire, fuelling fault or oil or coolant consumption before fitting a new sensor
Replace the catalytic converter only if testing shows it is degraded and the cause has been found and corrected

Can I keep driving?

Low severity

The car can normally be driven while you book it in for diagnosis. Have it checked sooner if the engine runs roughly, misfires or the warning light flashes, as that could damage the catalytic converter.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.