Ageing, contaminated or sluggish oxygen sensor (bank 2 sensor 3); Damaged, corroded or loose sensor wiring or connector, or a poor heater circuit supply or earth; Exhaust leak near the sensor letting in outside air and skewing readings; Sensor contaminated by oil, coolant, silicone or fuel additives; Underlying fuel trim or mixture fault on bank 2 (for example a vacuum leak, injector fault or fuel delivery problem); Failing catalytic converter affecting gas readings at the sensor; Fault in the engine control unit.

P019C

O2 Sensor Delayed Response - Rich to Lean Bank 2 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
9C: FaultThe specific fault in that area

What it means

P019C means the engine control unit saw the bank 2 sensor 3 oxygen sensor react too slowly when the exhaust changed from rich to lean. Bank 2 is the side of the engine that does not contain cylinder 1. Sensor 3 is normally a further downstream sensor, but its exact position depends on the model and exhaust layout, so confirm it for the vehicle before replacing anything.

Symptoms

Engine warning light on
Usually no obvious change in driving
Slightly higher fuel consumption in some cases
Other oxygen sensor or catalyst codes stored alongside it
Possible failed emissions test

Possible causes

Ageing, contaminated or sluggish oxygen sensor (bank 2 sensor 3)likely
Damaged, corroded or loose sensor wiring or connector, or a poor heater circuit supply or earthlikely
Exhaust leak near the sensor letting in outside air and skewing readingspossible
Sensor contaminated by oil, coolant, silicone or fuel additivespossible
Underlying fuel trim or mixture fault on bank 2 (for example a vacuum leak, injector fault or fuel delivery problem)possible
Failing catalytic converter affecting gas readings at the sensorrare
Fault in the engine control unitrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine load, temperature and speed when the fault set.
Look up which sensor is bank 2 sensor 3 on this model and engine, and check it is the correct one before testing.
Inspect the sensor wiring, connector and routing for chafing, heat damage, corrosion, water ingress or loose pins.
Check the exhaust for leaks, especially around joints, flanges and the area upstream of the sensor.
Check the sensor heater circuit for supply, earth and resistance against the manufacturer's specification.
Watch live data for the sensor and compare its switching speed and voltage with the other sensors on the same bank during a snap throttle test or overrun.
Check short and long term fuel trims for bank 2, and look for vacuum leaks, injector faults or fuel pressure problems.
Look for signs of oil, coolant or fuel contamination on the sensor and check for other faults that could cause it.

How to fix

Replace the bank 2 sensor 3 oxygen sensor if it is slow and the wiring and exhaust have checked out.
Repair or replace damaged wiring, connectors or terminals, and restore the heater circuit supply or earth.
Repair any exhaust leak near the sensor, using the correct gaskets and fixings.
Fix the underlying mixture, vacuum or fuel delivery fault, and replace any sensor that has been contaminated.
If the catalyst is confirmed as failing, replace it with a suitable approved unit.
Clear the codes after the repair and road test to confirm that the fault does not return.

Can I keep driving?

Low severity

The car can usually be driven normally while you arrange a repair. Do not leave it for long, as the underlying fault could raise emissions and fuel use or harm the catalyst.

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