Ageing or contaminated Bank 1 Sensor 3 oxygen sensor with slow response; Damaged wiring, poor connector contact or corrosion in the sensor circuit; Exhaust leak near the sensor letting in air and distorting the reading; Sensor contaminated by oil, coolant, silicone or fuel additives; Underlying fuelling or combustion fault, such as a misfire or a rich or lean running condition, affecting the exhaust gas; Faulty sensor heater circuit or heater supply, causing the sensor to run too cool; Engine control unit fault or outdated calibration, where the manufacturer has issued an update for this code.

P019B

O2 Sensor Delayed Response - Lean to Rich 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
9B: FaultThe specific fault in that area

What it means

P019B is a generic powertrain code meaning the Bank 1 Sensor 3 oxygen sensor is slow to respond when the exhaust changes from lean to rich. The control unit compares how quickly the sensor signal switches against an expected response time, and sets the code when the delay is too long. Sensor 3 is normally a further downstream sensor, but its position and role depend on the exhaust layout of the model and engine.

Symptoms

Engine management light on
Little or no change in driveability in many cases
Possible slight rise in fuel consumption
Other oxygen sensor or catalyst efficiency codes stored alongside
Failed emissions test

Possible causes

Ageing or contaminated Bank 1 Sensor 3 oxygen sensor with slow responselikely
Damaged wiring, poor connector contact or corrosion in the sensor circuitlikely
Exhaust leak near the sensor letting in air and distorting the readingpossible
Sensor contaminated by oil, coolant, silicone or fuel additivespossible
Underlying fuelling or combustion fault, such as a misfire or a rich or lean running condition, affecting the exhaust gaspossible
Faulty sensor heater circuit or heater supply, causing the sensor to run too coolpossible
Engine control unit fault or outdated calibration, where the manufacturer has issued an update for this coderare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including engine load, coolant temperature and fuel trims
Check for related codes such as misfires, fuel trim faults, heater circuit faults or catalyst efficiency codes and deal with those first
Identify which sensor is Bank 1 Sensor 3 on this model, as the exhaust layout varies by vehicle and engine
Inspect the sensor wiring and connector for chafing, heat damage, water ingress and corrosion
Check the exhaust for leaks upstream of and around the sensor, including joints and gaskets
Check the sensor heater circuit supply, fuse and resistance against the manufacturer's specification
View live data and watch the sensor voltage switching during a controlled change in mixture, comparing it with a known good sensor response
Check for signs of contamination on the sensor and for coolant or oil consumption that could cause it

How to fix

Replace the Bank 1 Sensor 3 oxygen sensor if it is confirmed slow or contaminated
Repair or replace damaged wiring, terminals or connectors in the sensor circuit
Repair exhaust leaks and replace faulty gaskets or sections
Fix any underlying misfire, fuelling or engine fault that is contaminating the sensor, then clear the code and retest
Update the engine control unit calibration only if the manufacturer lists an outdated calibration as a known cause for this fault

Can I keep driving?

Low severity

The car can usually be driven normally while you book it in for diagnosis. Do not leave it for long, as an underlying fuelling or exhaust fault could affect emissions and the catalytic converter.

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