#EGR
6 posts in Car Diagnostics blog about "EGR" — OBD-II diagnostics, DTC codes, repair. ← All posts
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Surging at a constant speed: fuel trim, torque converter or EGR
A gentle rhythmic pulsing at a steady cruise, with your foot still. The frequency of the pulse points at which system is hunting.
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P0400 and P0403: EGR flow malfunction and control circuit
P0400 says the exhaust gas is not flowing. P0403 says the valve is not being commanded properly. One is usually carbon; the other is usually electrical.
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P0404: EGR position sensor range/performance explained
P0404 compares commanded EGR position against measured position. Carbon, not electronics, is behind most of them — and cleaning beats replacing far more often than parts sellers admit.
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P0405 and P0406: EGR position sensor A low and high
These are the feedback side of the EGR system. Without a trustworthy position signal the ECU is commanding a valve blind, and it will not do that for long.
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EGR valve and EGR cooler leak: codes P0401, P0402, P0404 and why diesel Passat/A6 "got sooted up"
How to diagnose EGR via OBD-II: difference between P0401 (low flow) and P0402 (high), EGR cooler leak, why "EGR delete" is a short fix with long problems.
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Diesel Engine Power Loss: 10 Causes and Step-by-Step Diagnosis
Why a diesel car does not pull, how to quickly distinguish turbo, EGR, DPF or injector issues, and which DTC codes to read first.