Common Symptoms
- Check Engine Light illuminated
- Rough idle or engine hesitation
- Poor acceleration or reduced engine performance
- Increased NOx emissions
- Failed emissions test
Most Likely Root Causes
- Faulty EGR position sensor B
- Damaged or corroded wiring harness to EGR sensor B
- Poor electrical connection at EGR sensor B connector
- Shorted sensor signal wire to ground
- Failed powertrain control module
Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.
AI walks you through every test — one step at a time. Plans start at $12.95/mo.
Component Location
EGR sensor B is typically mounted on or near the EGR valve assembly on the intake manifold or EGR cooler outlet.
Manufacturer Notes
Some vehicles use dual EGR position sensors where sensor B monitors a secondary EGR valve or different point in the EGR system.
Also diagnosing J1939 SPN/FMI codes?
Heavy-duty trucks often throw both OBD-II and J1939 faults simultaneously. AI Diesel Tech handles both protocols in a single guided session.
AI Diesel Tech — The Technician's Diagnostic Engine
AI Diesel Tech diagnostic logic is built by an ASE Certified Diesel Technician. Professional-grade OBD-II and J1939 fault analysis — trusted by technicians nationwide, used in shops, fleets, and training programs.
Get AI-Guided Diagnosis for P0407
The diagnostic engine walks you through every physical test — step by step, on your phone, at the truck.