Faulty secondary air switching or combi valve solenoid (open or shorted coil); Damaged wiring, chafing or corrosion in the valve or relay circuit; Corroded, loose or water-damaged connector at the valve, pump or relay; Faulty secondary air pump relay or blown fuse in the circuit; Seized or failed air pump drawing excess current and affecting the circuit; Fault inside the engine control unit driver for the circuit.

P0419

AIR System Control B Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
19: FaultThe specific fault in that area

What it means

P0419 is the generic code for a fault in the control circuit of the 'B' part of the secondary air injection (AIR) system. This is usually the switching or combi valve, or the control for the second bank or second air path, depending on the vehicle. The engine control unit has seen an electrical fault on that circuit, such as an open circuit, a short or a wrong feedback signal, when it commanded the valve or relay.

Symptoms

Malfunction indicator lamp on
Secondary air pump running at the wrong time, constantly, or not at all
Whining or buzzing from the air pump on a cold start
Possible rough or unstable idle on a cold start
Emissions test failure
Other secondary air or lambda-related codes stored alongside

Possible causes

Faulty secondary air switching or combi valve solenoid (open or shorted coil)likely
Damaged wiring, chafing or corrosion in the valve or relay circuitlikely
Corroded, loose or water-damaged connector at the valve, pump or relaylikely
Faulty secondary air pump relay or blown fuse in the circuitpossible
Seized or failed air pump drawing excess current and affecting the circuitpossible
Fault inside the engine control unit driver for the circuitrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine temperature and conditions when the fault set, and check for related secondary air codes.
Look up the layout for the specific model and engine to identify which valve, relay and pump 'B' refers to, as this varies between manufacturers.
Visually inspect the wiring, connectors, relay and fuse for the secondary air system for damage, moisture, corrosion and loose pins.
Check the relevant fuse and relay, and swap the relay with a known good identical one if the layout allows.
Use a scan tool's actuator test, if supported, to command the valve and pump and listen and feel for operation.
With the connector unplugged, measure the valve solenoid resistance and compare it with the manufacturer's specification.
Check the supply voltage, earth and control signal at the valve connector while it is commanded, and test the wiring back to the control unit for open circuits and shorts.
Check the air pump and hoses for blockage, water ingress or seizure, as this may be part of the cause.

How to fix

Replace the faulty switching or combi valve.
Repair or replace damaged wiring and clean or replace corroded connectors.
Replace a faulty relay or blown fuse, after finding out why it failed.
Replace a seized or failed air pump if it is overloading the circuit.
Have the control unit tested and repaired or replaced only after the wiring and components are confirmed good.

Can I keep driving?

Low severity

The car can normally be driven as the fault mainly affects cold-start emissions, but book it in soon. Repeated pump or valve faults can leave other secondary air faults unresolved and cause an emissions test failure.

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