Secondary Air Injection Relay B Circuit Malfunction
The P0419 code indicates a malfunction in the secondary air injection system relay 'B' circuit. This system pumps fresh air into the exhaust to reduce emissions during cold starts. The relay controls power to the air pump or switching valve. A circuit fault (open, short, or high resistance) prevents proper operation, often due to a failed relay, wiring issues, or a blown fuse.
01. Most Common Causes
- Faulty secondary air injection relay B
- Blown fuse or wiring issues (open/short)
- Corroded or loose relay connector
- Failed engine control module (rare)
02. Symptoms You Will Notice
- Check Engine Light on
- Failed emissions test
- Rough idle or hesitation on cold start
- Possible reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0419 is present.
Step 2: Inspect relay B and its fuse; test for power and ground.
Step 3: Check wiring and connectors for damage or corrosion.
Step 4: Swap relay B with a known good relay to test.
Step 5: If issue persists, test the air pump and switching valve.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but the vehicle may fail emissions testing and cold-start emissions will increase. Driving short term is okay, but repair soon to avoid further issues.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on whether it's a relay, fuse, or wiring repair.