EGR systems — electrical command vs actual gas flow
EGR position says 40% commanded, but the engine behaves as if no exhaust gas is flowing. Is the valve electrically dead, mechanically blocked or is the air-path data misleading?
What this lesson covers
CORE TEACHING EGR purpose and NOx reduction; vacuum vs electronic EGR; motor/solenoid drive; position sensor; EGR cooler/bypass; MAF/MAP response to EGR; sticking/carbon; plausibility DTCs; low-pressure/high-pressure EGR awareness on diesels. PRACTICAL DEMONSTRATIONS AND TESTS Command EGR with scan tool; watch position feedback, MAF and MAP; test motor/solenoid power, ground and control; scope PWM/position signal if useful; inspect flow passages where diagnosis points there. ADVANCED / SCAN TOOL LAYER Bidirectional EGR command; MAF/MAP graph; PWM/current; position-sensor scope. KEY DIAGNOSTIC QUESTIONS Did the valve receive command? Did it physically move? Did actual gas flow change? Do MAF/MAP reactions support the command? MUST-COVER CHECKPOINTS Command; position feedback; airflow consequence; electrical drive; mechanical passage; cooler/bypass context; prove flow not just motor movement.
What you will be able to do
EGR position says 40% commanded, but the engine behaves as if no exhaust gas is flowing. Is the valve electrically dead, mechanically blocked or is the air-path data misleading?
Where it sits in the programme
- Builds on
- Lesson 41: Lambda / oxygen sensors and fuel-control feedback
- Feeds into
- Lesson 43: DPF / GPF sensing — soot, ash, differential pressure and EGT