What causes fault code P0419?

• Most likely: Faulty secondary air injection relay (internal coil failure) • Likely: Blown fuse for the SAI system (often caused by a seizing pump) • Possible: Corrosion or backed-out pins in the relay socket or ECU connector • Rare: Wiring harness issues (short to ground or voltage in the control wire)

How do you fix fault code P0419?

VISUAL INSPECTION: Check the SAI pump fuse and relay. Inspect the relay socket for signs of overheating or corrosion. RELAY MEASUREMENT: Remove the relay and measure the coil resistance (terminals 85 and 86). Typical values are 40-100 Ohms. Verify 12V supply to the control circuit with ignition on. WIRING: Check continuity in the signal wire between the relay socket and the ECU. Ensure there is no short to ground. ADVANCED DIAGNOSIS: Use a scan tool to perform a 'Component Test' or 'Active Test' of the SAI relay and listen for relay clicking or pump activation. REPLACEMENT: Replace relay 'B'. If the fuse blows repeatedly, inspect the SAI pump for high current draw or seizure.

Powertrain (Engine & Gearbox)Standard EOBD

P0419 - Secondary Air Injection System Control Circuit B Malfunction

Q: What are the symptoms of fault code P0419?

• Check engine light (MIL) illuminated • Whining or fan-like noise during cold start (if pump is stuck on) • Absence of pump noise when expected during cold start • Failed emissions test due to slow catalyst warm-up

Last updated:1 February 2026

Related:B, Secondary Air Pump, Engine Control Unit (ECU), Fuse for SAI system

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0400

Exhaust Gas Recirculation Flow Malfunction

P0401

Exhaust Gas Recirculation (EGR) Flow Insufficient Detected

P0402

Exhaust Gas Recirculation Flow Excessive Detected

P0403

Exhaust Gas Recirculation (EGR) Control Circuit

Technical Description

Diagnostic Trouble Code (DTC) P0419 points to an electrical malfunction in the Secondary Air Injection (SAI) pump relay 'B' control circuit. The SAI system's purpose is to inject ambient air into the exhaust manifold during cold starts to promote the oxidation of HC and CO and to reach catalyst 'light-off' temperature faster. The PCM (Powertrain Control Module) monitors the continuity and voltage of the relay circuit. If the PCM detects an open circuit, short to ground, or short to voltage when the relay is commanded on or off, P0419 will trigger. This is a purely electrical circuit fault, distinct from mechanical flow issues (P0411).

Possible Causes

Faulty secondary air injection relay (internal coil failure)

Blown fuse for the SAI system (often caused by a seizing pump)

Corrosion or backed-out pins in the relay socket or ECU connector

Wiring harness issues (short to ground or voltage in the control wire)

Symptoms

Check engine light (MIL) illuminated

Whining or fan-like noise during cold start (if pump is stuck on)

Absence of pump noise when expected during cold start

Failed emissions test due to slow catalyst warm-up

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P0419 - Secondary Air Injection System Control Circuit B Malfunction

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P0419 - Secondary Air Injection System Control Circuit B Malfunction

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