What Does P0419 Mean?
The PCM has detected a malfunction in the secondary air injection system relay B circuit. Relay B controls power distribution to the AIR system components on bank 2 (or the secondary AIR pump on some applications). Without proper relay operation, the AIR pump or switching valves cannot be energized during cold-start emission reduction. The driver will see the check engine light with no noticeable performance impact.
Common Causes
35%
Failed AIR system relay B (stuck open or welded contacts)
25%
Open or corroded wiring between the PCM and relay B
20%
Blown fuse feeding the AIR relay B coil or contacts
12%
Corroded relay socket terminals in the fuse/relay box
8%
PCM relay driver circuit failure
Diagnostic Steps
1
Locate the AIR relay B in the underhood fuse/relay box (consult the fuse box lid diagram). Remove and inspect the relay terminals and socket for corrosion, overheating, or carbon tracking.
2
Test the relay independently: apply 12V to the coil terminals (pins 85/86) and listen for a click. Use a multimeter to verify continuity across the switch terminals (pins 30/87) when energized.
3
Check the relay coil control wire at the PCM connector for proper ground-side switching. With key on, command the AIR system and verify the PCM is pulling the relay control wire to ground.
4
Verify the fuse providing B+ to the relay contact side (pin 30) is intact and delivering battery voltage. Check for voltage drop across the fuse — more than 0.1V indicates a poor connection.
5
Swap the AIR relay with another identical relay in the box (e.g., AC or fuel pump relay) as a quick functional test. If the code clears with a known-good relay, replace the original.
Estimated Repair Cost
$30 - $250
Parts + labor, varies by vehicle and location
The PCM has detected a malfunction in the secondary air injection system relay B circuit. Relay B controls power distribution to the AIR system components on bank 2 (or the secondary AIR pump on some applications). Without proper relay operation, the AIR pump or switching valves cannot be energized ...
The most common cause of P0419 (Secondary Air Injection System Relay "B" Circuit Malfunction) is: Failed AIR system relay B (stuck open or welded contacts)
Typical repair costs for P0419 range from $30 to $250, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving. The AIR system is for emissions reduction only. If the relay is welded closed, the AIR pump may run continuously, causing slight additional noise but no safety concern.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0419 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emission Control System
Difficulty
Type
Generic (SAE)
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